FIRST SUPPLEMENTAL INDENTURE

Exhibit 4.2

EXECUTION VERSION

ENERSYS

ISSUER

THE BANK OF NEW YORK

TRUSTEE

FIRST SUPPLEMENTAL INDENTURE

Dated as of May 28, 2008

To

INDENTURE

Dated as of May 28, 2008

3.375% CONVERTIBLE SENIOR NOTES DUE 2038

ENERSYS

Certain Sections of this Indenture relating to Sections 310 through 318 of the

Trust Indenture Act of 1939:

Note: This reconciliation and tie shall not, for any purpose, be deemed to be a part of this Indenture.

TABLE OF CONTENTS

ARTICLE 1

D EFINITIONS AND O THER P ROVISIONS OF G ENERAL A PPLICATION

ARTICLE 2

N OTE F ORMS

ARTICLE 3

T HE N OTES

i

ARTICLE 4

D ISCHARGE

ARTICLE 5

R EMEDIES

ARTICLE 6

[ RESERVED .]

ARTICLE 7

C ONSOLIDATION , M ERGER , C ONVEYANCE , T RANSFER OR L EASE

ARTICLE 8

S UPPLEMENTAL I NDENTURES

ii

ARTICLE 9

H OLDERS L ISTS AND B Y T RUSTEE AND C OMPANY

ARTICLE 10

C OVENANTS

ARTICLE 12

C ONVERSION OF N OTES

iii

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FIRST SUPPLEMENTAL INDENTURE, dated as of May 28, 2008 (this “ Supplemental Indenture ,” together with the Base Indenture (as defined below), the “ Indenture ”), between ENERSYS, a corporation duly organized and existing under the laws of the State of Delaware, having its principal office at 2366 Bernville Road, Reading, Pennsylvania 19605 (herein called the “ Company ”), and THE BANK OF NEW YORK, as Trustee hereunder (herein called the “ Trustee ”).

RECITALS OF THE COMPANY

WHEREAS, the Company has heretofore executed and delivered to the Trustee an Indenture, dated as of May 28. 2008 (the “ Base Indenture ”).

WHEREAS, the Company desires and has requested the Trustee pursuant to Section 14.01 of the Base Indenture to join with them in the execution and delivery of this Supplemental Indenture in order to supplement the Base Indenture as and to the extent set forth herein to provide for the issuance and the terms of the Company’s 3.375% Convertible Senior Notes due 2038 (herein called the “ Notes ”).

WHEREAS, Section 14.01(p) of the Base Indenture provides that a supplemental indenture may be entered into by the Company and the Trustee without the consent of any Holders to establish the form and terms of Securities (as defined in the Base Indenture) of any series as permitted in Section 3.01 of the Base Indenture.

WHEREAS, the execution and delivery of this Supplemental Indenture has been duly authorized by a Board Resolution of the Company, and all things necessary to make the Notes, when the Notes are executed by the Company and authenticated and delivered hereunder, the valid obligations of the Company have been done. Further, all things necessary to duly authorize the issuance of the Common Stock issuable upon the conversion of the Notes, and to duly reserve for issuance the amount of cash and the number of shares of Common Stock (or, at the election of the Company, the amount of cash or the number of shares of Common Stock) issuable upon such conversion, have been done.

NOW, THEREFORE, THIS INDENTURE WITNESSETH:

For and in consideration of the premises and the purchase of the Notes by the Holders thereof, it is mutually covenanted and agreed, for the equal and proportionate benefit of all Holders of the Notes, as follows:

ARTICLE 1

D EFINITIONS AND O THER P ROVISIONS OF G ENERAL A PPLICATION

Section 1.01. Definitions.

For all purposes of this Supplemental Indenture, except as otherwise expressly provided or unless the context otherwise requires:

(a) capitalized terms used but not defined herein shall have the respective meanings assigned to them in the Trust Indenture Act or the Base Indenture;

(b) the terms defined in this Article 1 have the meanings assigned to them in this Article 1 and include the plural as well as the singular;

(c) all accounting terms not otherwise defined herein have the meanings assigned to them in accordance with generally accepted accounting principles in the United States, and, except as otherwise herein expressly provided, the term “generally accepted accounting principles” with respect to any computation required or permitted hereunder shall mean such accounting principles as are generally accepted at the date of such computation; and

(d) all other terms used in this Supplemental Indenture, which are defined in the Trust Indenture Act or which are by reference therein defined in the Securities Act (except as herein otherwise expressly provided or unless the context otherwise requires), shall have the meanings assigned to such terms in the Trust Indenture Act and in the Securities Act as in force at the date of the execution of this Indenture. The words “herein,” “hereof” and “hereunder” and other words of similar import refer to this Indenture as a whole and not to any particular Article, Section or other subdivision.

“ Accreted Principal Amount ” means the Original Principal Amount at any time prior to June 1, 2015, and the Original Principal Amount as adjusted upward for accretion as described in Section 3.04 at any time on or after June 1, 2015.

“ Additional Notes ” means an unlimited amount of Notes (other than the Initial Notes) issued under this Indenture in accordance with Section 3.06, as part of the same series as the Initial Notes.

“ Additional Shares ” has the meaning specified in Section 12.01(e).

“ Adjustment Determination Date ” has the meaning specified in Section 12.04(i).

“ Adjustment Event ” has the meaning specified in Section 12.04(i).

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“ Agent Member ” means any member of, or participant in, the Depositary.

“ Applicable Procedures ” means, with respect to any transfer or transaction involving a Global Note or beneficial interest therein, the rules and procedures of DTC or any successor Depositary, in each case to the extent applicable to such transaction and as in effect from time to time.

“ Base Indenture ” has the meaning ascribed to it in the first paragraph under the caption “Recitals of the Company.”

“ Board of Directors ” means either the board of directors of the Company or any duly authorized committee of that board, as applicable.

“ Board Resolution ” means a copy of a resolution certified by the Secretary or an Assistant Secretary of the Company to have been duly adopted by the Board of Directors and to be in full force and effect on the date of such certification, and delivered to the Trustee.

“ Capital Stock ” means, for any entity, any and all shares, interests, rights to purchase, warrants, options, participations or other equivalents of or interests in (however designated) stock issued by that entity.

“ Cash Percentage ” means the percentage of the Daily Conversion Value in excess of the Principal Portion that the Company will elect to satisfy (or be deemed to have elected to satisfy) in cash, as specified in a Consideration Notice pursuant to Section 12.02(b) (or zero percent (0%) if no Cash Percentage is specified in a Consideration Notice).

“ Certificated Note ” means a certificated Note registered in the name of the Holder thereof and issued in accordance with this Supplemental Indenture, substantially in the form of Section 2.02 hereof, except that such Note will not bear the Global Note Legend.

“ close of business ” means 5:00 p.m. (New York City time).

“ Code ” means the Internal Revenue Code of 1986 as in effect on the date hereof.

“ Combination Settlement ” means settlement of the Company’s Conversion Obligation by delivering (a) cash for the Principal Portion and (b) for the excess, if any, of the Conversion Obligation above the Principal Portion, a combination of cash and shares of Common Stock (or units of Reference Property) based on the Cash Percentage specified (or deemed to have been specified) in the applicable Consideration Notice.

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“ Commission ” means the United States Securities and Exchange Commission.

“ Common Stock ” means the Common Stock, par value $0.01 per share, of the Company authorized at the date of this instrument as originally executed or as such stock may be constituted from time to time. Subject to the provisions of Section 12.10, shares issuable upon conversion of Notes shall include only shares of Common Stock or shares of any class or classes of common stock resulting from any reclassification or reclassifications thereof; provided , however , that if at any time there shall be more than one such resulting class, the shares so issuable on conversion of Notes shall include shares of all such classes, and the shares of each such class then so issuable shall be substantially in the proportion which the total number of shares of such class resulting from all such reclassifications bears to the total number of shares of all such classes resulting from all such reclassifications.

“ common stock ” includes any stock of any class of Capital Stock which has no preference in respect of dividends or of amounts payable in the event of any voluntary or involuntary liquidation, dissolution or winding up of the issuer thereof and which is not subject to redemption by the issuer thereof.

“ Company ” means the Person named as the “ Company ” in the first paragraph of this instrument until a successor Person shall have become such pursuant to the applicable provisions of this Indenture, and thereafter “ Company ” shall mean such successor Person.

“ Consideration Notice ” has the meaning specified in Section 12.02(b).

“ Contingent Interest ” means interest that accrues and is payable as provided in Section 3.03.

“ Contingent Payment Debt Regulations ” has the meaning specified in Section 10.08(a).

“ Continuing Directors ” means (a) individuals who on the Issue Date constituted the Board of Directors and (b) any new directors whose election to the Board of Directors or whose nomination for election by the stockholders of the Company was approved by at least a majority of the directors then still in office (or a duly constituted committee thereof), either who were directors on the Issue Date or whose election or nomination for election was previously so approved.

“ Conversion Agent ” means any Person authorized by the Company to convert Notes in accordance with Article 12. The Company has initially appointed the Trustee as its Conversion Agent pursuant to Section 10.02.

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“ Conversion Consideration ” has the meaning specified in Section 12.02(c).

“ Conversion Date ” has the meaning specified in Section 12.02(d).

“ Conversion Obligation ” means the obligation of the Company to deliver the consideration due under Article 12 upon a conversion of the Notes in accordance herewith.

“ Conversion Price ” means at any given time the amount equal to $1,000 divided by the then applicable Conversion Rate.

“ Conversion Rate ” has the meaning specified in Section 12.01(a).

“ Custodian ” means the Trustee, as custodian with respect to the Notes in global form, or any successor entity thereto.

“ Daily Conversion Value ” means, for each of the 25 consecutive VWAP Trading Days during the Observation Period, one-twenty-fifth (1/25) of the product of (a) the applicable Conversion Rate and (b) the Daily VWAP of the Common Stock (or the Reference Property pursuant to Section 12.10) on such VWAP Trading Day, as determined by the Company. Any determination of the Daily Conversion Values by the Company shall be conclusive absent manifest error.

“ Daily Settlement Amount ” means, for each of the 25 VWAP Trading Days during the Observation Period,

(a) an amount of cash equal to the lesser of (i) the quotient of the Accreted Principal Amount per $1,000 Original Principal Amount as of such VWAP Trading Day and 25 and (ii) the Daily Conversion Value for such VWAP Trading Day (the “ C !Principal Portion ”); and

(b) if such Daily Conversion Value for such VWAP Trading Day exceeds the Principal Portion, either:

(i) if the Cash Percentage equals 0%, a number of shares of Common Stock (or the Reference Property pursuant to Section 12.10) (the “ Maximum Deliverable Shares ”) equal to (1) the difference between such Daily Conversion Value and the Principal Portion, divided by (2) the Daily VWAP of the Common Stock (or the Reference Property pursuant to Section 12.10) for such VWAP Trading Day, or

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(ii) if the Cash Percentage is greater than 0%, (1) an amount of cash equal to the product of the Cash Percentage and the Maximum Deliverable Shares and (2) a number of shares of Common Stock (or the Reference Property pursuant to Section 12.10) equal to the product of (x) 100% minus the Cash Percentage and (y) the Maximum Deliverable Shares.

“ Daily VWAP ” of the Common Stock (or Reference Property) means, for each of the 25 consecutive VWAP Trading Days during the Observation Period, the per share volume-weighted average price as displayed under the heading “Bloomberg VWAP” on Bloomberg page ENS.N <equity> AQR (or any equivalent successor page) in respect of the period from the scheduled open of trading on the principal trading market for the Common Stock to the scheduled close of trading on such market on such VWAP Trading Day (without regard to after-hours trading), or if such volume-weighted average price is unavailable, the market value of one share of the Common Stock (or one unit of Reference Property consisting of marketable equity securities) on such VWAP Trading Day using a volume-weighted method (or, in the case of Reference Property consisting of cash, the amount of such cash or in the case of Reference Property other than marketable equity securities or cash, the market value thereof), in each case as determined by a nationally recognized independent investment banking firm retained for this purpose by the Company.

“ Default ” means any event which is, or after notice or lapse of time or both would become, an Event of Default pursuant to Section 5.01.

“ Defaulted Interest ” has the meaning specified in Section 3.10.

“ Delivery Date ” has the meaning specified in Section 12.04(l).

“ Depositary ” means, with respect to Notes issuable in whole or in part in the form of one or more Global Notes, a clearing agency registered under the Exchange Act that is designated to act as Depositary for such Notes as contemplated by Section 3.07. C !

“ Distributed Property ” has the meaning specified in Section 12.04(c).

“ DTC ” means The Depository Trust Company, a New York corporation, or any successor.

“ Effective Date ” means the date on which a Fundamental Change occurs or becomes effective.

“ Event of Default ” has the meaning specified in Section 5.01.

“ Ex-Date ” means, with respect to any distribution on the Common Stock, the first date on which the shares of the Common Stock trade on the relevant exchange or in the relevant market, regular way, without the right to receive the issuance or distribution in question.

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“ Exchange Act ” means the Securities Exchange Act of 1934 and any statute successor thereto, in each case as amended from time to time.

“ Exchange Election ” has the meaning specified in Section 12.02(c).

“ Existing Credit Facilities ” means the credit facilities entered into by EnerSys Capital, Inc. with various lending institutions in effect on the Issue Date.

“ Extension Fee ” has the meaning specified in Section 5.02.

“ Extension Right ” has the meaning specified in Section 5.02.

“ Financial Institution ” has the meaning specified in Section 12.02(c).

“ Fundamental Change ” will be deemed to have occurred at the time after the Issue Date if any of the following occurs:

(1) any Person acquires beneficial ownership, directly or indirectly, through a purchase, tender or exchange offer, merger or other acquisition, transaction or series of transactions, of shares of the Company’s Capital Stock entitling the Person to exercise 50% or more of the total voting power of all shares of the Company’s Capital Stock entitled to vote generally in elections of directors and files a Schedule 13D or Schedule TO or any other schedule, form or report under the Exchange Act disclosing such beneficial ownership or the Company otherwise knows of such beneficial ownership; provided , however , that a Fundamental Change shall not occur as a result of this clause (1) if clause (2) also applies in which case clause (2) below shall apply (for purposes of this clause (1), whether a Person is a “beneficial owner” shall be determined in accordance with Rule 13d-3 under the Exchange Act, and “Person” shall include any syndicate or group that would be deemed to be a “person” under Section 13(d)(3) of the Exchange Act); or

(2) the Company (i) merges or consolidates with or into any other Person, another Person merges with or into the Company, or the Company conveys, sells, transfers or leases all or substantially all of the Company’s assets to another Person or (ii) engages in any recapitalization, reclassification or other transaction in which all or substantially all of the Common Stock is exchanged for or converted into cash, securities or other property, in each case other than any merger or consolidation:

(x) that does not result in a reclassification, conversion, exchange or cancellation of the Company’s outstanding Common Stock and pursuant to which the consideration received by holders of the Company’s Common Stock immediately prior to the transaction entitles such holders to exercise, directly or indirectly, 50% or more of the voting

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power of all shares of Capital Stock entitled to vote generally in the election of directors of the continuing or surviving corporation immediately after such transaction in substantially the same proportions as their respective ownership of the Company’s voting securities immediately prior to the transaction; or

(y) which is effected solely to change the Company’s jurisdiction of incorporation and results in a reclassification, conversion or exchange of outstanding shares of the Common Stock solely into shares of common stock of the surviving entity; or C !

(3) the first day on which a majority of the members of the Company’s Board of Directors does not consist of Continuing Directors; or

(4) the Company is liquidated or dissolved or holders of the Common Stock approve any plan or proposal for the Company’s liquidation or dissolution; or

(5) if shares of the Common Stock, or shares of any other common stock into which the Notes are convertible pursuant to the terms of this Supplemental Indenture, are not listed for trading on any of the New York Stock Exchange, the NASDAQ Global Market or the NASDAQ Global Select Market (or any of their respective successors).

“ Fundamental Change Repurchase Date ” has the meaning specified in Section 11.09(a).

“ Fundamental Change Repurchase Notice ” has the meaning specified in Section 11.09(a)(i).

“ Fundamental Change Repurchase Notice Information ” has the meaning specified in Section 11.09(b).

“ Fundamental Change Repurchase Price ” has the meaning specified in Section 11.09(a).

“ Fundamental Change Repurchase Right Notice ” has the meaning specified in Section 11.09(b).

“ Global Note ” means a Note bearing the Global Note Legend that is registered in the Securities Register in the name of a Depositary or a nominee thereof.

“ Global Note Legend ” means the legend set forth in Section 2.02, which is required to be placed on all Global Notes issued under this Supplemental Indenture.

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“ Holder ” means the Person in whose name the Note is registered in the Securities Register.

“ Indenture ” has the meaning specified in the first paragraph of this instrument.

“ Initial Notes ” means the first $150,000,000 aggregate Original Principal Amount of the Notes issued under this Supplemental Indenture on the date hereof. The Initial Notes and the Additional Notes shall be treated as a single class for all purposes under this Supplemental Indenture, and unless the context otherwise requires, all references to the Notes shall include the Initial Notes and any Additional Notes.

“ Interest ” means Regular Interest and Contingent Interest, if any.

“ Interest Payment Date ” means June 1 and December 1 of each year, beginning on December 1, 2008 and ending on June 1, 2015.

“ Interest Period ” has the meaning specified in Section 3.02.

“ Irrevocable Net Share Settlement Election ” has the meaning specified in Section 12.02(b).

“ Issue Date ” means May 28, 2008.

“ Last Reported Sale Price ” of the Common Stock on any date means the closing sale price per share (or if no closing sale price is reported, the average of the last bid and ask prices or, if more than one in either case, the average of the average last bid and the average last ask prices) on that date as reported in composite transactions for the principal U.S. national or regional securities exchange on which the Common Stock is traded, as determined by the Company. If the Common Stock is not listed for trading on a U.S. national or regional securities exchange on the relevant date, the “ Last Reported Sale Price ” shall be the average of the last quoted bid and ask prices for the Common Stock in the over-the-counter market on the relevant date as reported by Pink Sheets LLC or a similar organization. If the Common Stock is not so quoted, the “ Last Reported Sale Price ” shall be the average of the mid-point of the last bid and ask prices for the Common Stock on the relevant date from each of at least three nationally recognized independent investment banking firms, which may include any or all of the Underwriters, selected by the Company for this purpose. Any such determination shall be conclusive absent manifest error.

“ Make-Whole Fundamental Change ” means any transaction or event that occurs on or prior to June 6, 2015 and that constitutes a Fundamental Change pursuant to clauses (1), (2) or (5) under the definition thereof.

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“ Make-Whole Reference Date ” means with respect to any Make-Whole Fundamental Change, the earliest of the date on which such Make-Whole Fundamental Change is publicly announced, occurs or becomes effective.

“ Market Disruption Event ” means the occurrence or existence on any Scheduled Trading Day for the Common Stock of any suspension or limitation imposed on trading (by reason of movements in price exceeding limits permitted by the stock exchange or otherwise) in the Common Stock or in any options contracts or futures contracts relating to the Common Stock, and such suspension or limitation occurs or exists at any time within the 30 minutes prior to the closing time of the relevant exchange on such day.

“ Maturity, ” when used with respect to any Notes, means the date on which the principal of such Notes becomes due and payable as therein or herein provided, whether on the Maturity Date or by declaration of acceleration, exercise of the redemption right or repurchase right, set forth in Article 11 or otherwise.

“ Maturity Date ” means, with respect to the Notes, June 1, 2038.

“ Maximum Deliverable Shares ” has the meaning specified in the definition of Daily Settlement Amount.

“ Measurement Period ” (i) for purposes of determining whether the Company is required to pay Contingent Interest, has the meaning specified in Section 3.03(a) and (ii) for purposes of determining whether the Trading Price Condition has been met, the meaning specified in Section 12.01(a)(i).

“ Merger Event ” has the meaning specified in Section 12.10.

“ New Credit Facilities ” means any credit facilities entered into by the Company to refinance the Existing Credit Facilities.

“ Notes ” has the meaning ascribed to it in the second paragraph under the caption “Recitals of the Company.” Unless the context otherwise requires, all references to the Notes shall include the Initial Notes and any Additional Notes.

“ Notice of Conversion ” has the meaning specified in Section 12.02(d).

“ Notice of Redemption ” has the meaning specified in Section 11.03.

“ Observation Period ” means, with respect to any Notes:

(a) with respect to any Conversion Date occurring within the Optional Redemption Conversion Period, the 25 consecutive VWAP Trading Day period beginning on, and including, the Redemption Date (or if the Redemption Date is not a VWAP Trading Day, the next succeeding VWAP Trading Day); or

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(b) with respect to any Conversion Date occurring on or after the 30th Scheduled Trading Day prior to the Maturity Date of the Notes, the 25 consecutive VWAP Trading Day period beginning on, and including, the 27th Scheduled Trading Day prior to the Maturity Date (or if such day is not a VWAP Trading Day, the next succeeding VWAP Trading Day); or

(c) in all other instances, the 25 consecutive VWAP Trading Day period beginning on, and including, the third VWAP Trading Day after the related Conversion Date in respect of such Notes.

“ Opinion of Counsel ” means a written opinion of counsel, who may be an employee of or counsel to the Company, and who shall be reasonably acceptable to the Trustee.

“ Optional Redemption Conversion Period ” means the 15 calendar day period beginning on, and including, the 16th calendar day immediately preceding a Redemption Date.

“ Optional Put Repurchase Offer ” has the meaning specified in Section 11.08(a)(ii).

“ Optional Put Repurchase Date ” has the meaning specified in Section 11.08(a)(i).

“ Optional Put Repurchase Notice ” has the meaning specified in Section 11.08(a)(ii).

“ Optional Put Repurchase Price ” has the meaning specified in Section 11.08(a)(i).

“ Original Principal Amount ” means (a) with respect to the Initial Notes, the principal amount of the Initial Notes as of the Issue Date and (b) with respect to Additional Notes, if any, the principal amount of such Additional Notes on their date of issuance.

“ Outstanding, ” when used with respect to the Notes, means, as of the date of determination, all Notes theretofore authenticated and delivered under this Supplemental Indenture, except:

(a) Notes theretofore canceled by the Trustee or delivered to the Trustee for cancellation;

(b) Notes for the payment of which money in the necessary amount has been theretofore deposited with the Trustee or any Paying Agent (other than the Company) in trust or set aside and segregated in trust by the Company (if the Company shall act as its own Paying Agent) for the Holders of such Notes in accordance with the terms of this Supplemental Indenture;

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(c) Notes which have been paid pursuant to Section 3.09 or in exchange for or in lieu of which other Notes have been authenticated and delivered pursuant to this Supplemental Indenture;

(d) Notes converted into Common Stock pursuant to Article 12; and

(e) Notes redeemed or repurchased pursuant to Article 11;

provided , however , that in determining whether the Holders of the requisite principal amount of Outstanding Notes are present at a meeting of Holders for quorum purposes or have given any request, demand, authorization, direction, notice, consent or waiver hereunder, Notes owned by the Company or any other obligor upon the Notes or any Affiliate of the Company or such other obligor shall be disregarded and deemed not to be Outstanding, except that, in determining whether the Trustee shall be protected in relying upon any such determination as to the presence of a quorum or upon any such request, demand, authorization, direction, notice, consent or waiver, only Notes which a Responsible Officer of the Trustee has been notified in writing to be so owned shall be so disregarded. Notes so owned which have been pledged in good faith may be regarded as Outstanding if the pledgee is not the Company or any other obligor upon the Notes or any Affiliate of the Company or such other obligor, and the Trustee shall be protected in relying upon an Officers’ Certificate to such effect.

“ Paying Agent ” means any Person authorized by the Company to pay the principal of or Interest on any Notes on behalf of the Company and, except as otherwise specifically set forth herein, such term shall include the Company if it shall act as its own Paying Agent. The Company has initially appointed the Trustee as its Paying Agent pursuant to Section 10.02.

“ Person ” means any individual, corporation, limited liability company, partnership, joint venture, trust, estate, unincorporated organization or government or any agency or political subdivision thereof and any syndicate or group that would be deemed a “person” under Section 13(d)(3) of the Exchange Act.

“ Predecessor Note ” of any particular Note means every previous Note evidencing all or a portion of the same debt as that evidenced by such particular Note and, for the purposes of this definition, any Note authenticated and delivered under Section 3.09 in exchange for or in lieu of a mutilated, destroyed, lost or stolen Note shall be deemed to evidence the same debt as the mutilated, destroyed, lost or stolen Note.

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“ Press Release ” means any press release issued by the Company and disseminated to a reputable national newswire service.

“ Principal Portion ” has the meaning specified in the definition of Daily Settlement Amount.

“ Prospectus Supplement ” means the prospectus supplement dated May 21, 2008 to the prospectus dated May 19, 2008 relating to the offering and sale of the Notes.

“ Record Date ” means any Regular Record Date or Special Record Date.

“ Redemption Date ” when used with respect to any Note to be redeemed, means the date fixed by the Company for such redemption pursuant to this Indenture.

“ Redemption Price ” has the meaning specified in Section 11.01.

“ Reference Property ” has the meaning specified in Section 12.10(a).

“ Registrar ” means the Trustee, for the purpose of registering Notes and transfers of Notes.

“ Regular Interest ” has the meaning specified in Section 3.02.

“ Regular Record Date ” for Interest payable in respect of any Note on any Interest Payment Date means 5:00 p.m. New York time on May 15 or November 15 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date.

“ Scheduled Trading Day ” means a day that is scheduled to be a Trading Day on the principal U.S. national or regional securities exchange or market on which the Common Stock is listed or admitted for trading or, if the Common Stock is not listed or admitted for trading on any exchange or market, a Business Day.

“ Securities Act ” means the Securities Act of 1933 and any statute successor thereto, in each case as amended from time to time.

“ Significant Subsidiary ” means, with respect to any Person, a Subsidiary of such Person that would constitute a “significant subsidiary” as such term is defined under Rule 1-02 of Regulation S-X under the Securities Act and the Exchange Act.

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“ Special Record Date ” has the meaning specified in Section 3.10(a).

“ Spin-Off ” has the meaning specified in Section 12.04(c).

“ Stock Price ” means the price per share of Common Stock at the time of a Make-Whole Fundamental Change pursuant to which Additional Shares shall be added to the Conversion Rate as set forth in Section 12.01(e), which shall be equal to (i) if holders of the Common Stock receive only cash consideration for their shares of Common Stock (in a single per-share amount, other than with respect to appraisal and similar rights) in connection with a Make-Whole Fundamental Change, the cash amount paid per share of Common Stock and (ii) in all other cases, the average of the Last Reported Sale Prices of the Common Stock over the 10 consecutive Trading Day period ending on, and including, the Trading Day preceding the date on which such Make-Whole Fundamental Change occurs or becomes effective.

“ Successor Company ” has the meaning specified in Section 7.01(a).

“ Supplemental Indenture ” has the meaning specified in the first paragraph of this instrument.

“ Trading Day ” means a day during which (i) trading in the Common Stock generally occurs and (ii) there is no Market Disruption Event.

“ Trading Price ” of the Notes on any date of determination means the average of the secondary market bid quotations obtained by the Company or the Company’s agent for $2.0 million in Original Principal Amount of the Notes at approximately 3:30 p.m., New York City time, on such determination date from three independent nationally recognized securities dealers the Company selects, which may include any or all of the Underwriters; provided that if three such bids cannot reasonably be obtained, but two such bids are obtained, then the average of the two bids shall be used, and if only one such bid is obtained, that one bid shall be used. If at least one bid for $2.0 million in Original Principal Amount of the Notes cannot reasonably be obtained, then the Trading Price per $1,000 in Original Principal Amount of the Notes shall be deemed to be less than 98% of the product of the Last Reported Sale Price of the Common Stock and the applicable Conversion Rate. Any such determination shall be conclusive absent manifest error. Notwithstanding the foregoing, for purposes of Section 3.03 only, if two bids cannot reasonably be obtained for $2.0 million Original Principal Amount of the Notes from nationally recognized securities dealers that the Company has selected, but one such bid can reasonably be obtained, this one bid shall be used. If at least one bid cannot reasonably be obtained for $2.0 million Original Principal Amount of the Notes from a nationally recognized securities dealer or in the Company’s reasonable judgment the bid quotations are not indicative of the secondary market value of the Notes, then the Trading Price of

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the Notes will be deemed to equal the product of (i) the Conversion Rate then in effect and (ii) the average Last Reported Sale Price of the Common Stock over the five Trading Day period ending on such determination date.

“ Trading Price Condition ” has the meaning specified in Section 12.01(a)(i).

“ Trigger Event ” has the meaning specified in Section 12.04(c).

“ Trust Indenture Act ” means the Trust Indenture Act of 1939 as in force at the date as of which this instrument was executed; provided , however , that in the event the Trust Indenture Act of 1939 is amended after such date, “ Trust Indenture Act ” means, to the extent required by any such amendment, the Trust Indenture Act of 1939 as so amended.

“ Trustee ” means the Person named as the “Trustee” in the first paragraph of this instrument until a successor Trustee shall have become such pursuant to the applicable provisions of this Indenture, and thereafter “Trustee” shall mean such successor Trustee.

“ Underwriters ” means Goldman, Sachs & Co., Banc of America Securities LLC, Wachovia Capital Markets, LLC and PNC Capital Markets LLC.

“ VWAP Market Disruption Event ” means (i) a failure by the principal U.S. national or regional securities exchange or market on which the Common Stock is listed or admitted to trading to open for trading during its regular trading session or (ii) the occurrence or existence prior to 1:00 p.m. on any Scheduled Trading Day for the Common Stock for an aggregate one half-hour period of any suspension or limitation imposed on trading (by reason of movements in price exceeding limits permitted by the stock exchange or otherwise) in the Common Stock or in any options contracts or futures contracts relating to the Common Stock.

“ VWAP Trading Day ” means a day during which (i) trading in the Common Stock generally occurs on the principal U.S. national or regional securities exchange or market on which the Common Stock is listed or admitted for trading and (ii) there is no VWAP Market Disruption Event. If the Common Stock is not so listed or traded, then “ VWAP Trading Day ” means a Business Day.

Section 1.02. [Reserved].

Section 1.03. [Reserved].

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Section 1.04. Effect of Headings and Table of Contents.

The Article and Section headings herein and the Table of Contents are for convenience only and shall not affect the construction hereof.

Section 1.05. [Reserved].

Section 1.06. [Reserved].

Section 1.07. [Reserved].

Section 1.08. Conflict with Trust Indenture Act.

If any provision hereof limits, qualifies or conflicts with a provision of the Trust Indenture Act that is required under such Act to be a part of and govern this Supplemental Indenture, the latter provision shall control. If any provision of this Supplemental Indenture modifies or excludes any provision of the Trust Indenture Act that may be so modified or excluded, the latter provision shall be deemed to apply to this Supplemental Indenture as so modified or to be excluded, as the case may be.

Section 1.09. Successors and Assigns.

All covenants and agreements in this Supplemental Indenture by the Company shall bind its successors and assigns, whether so expressed or not.

Section 1.10. Separability Clause.

In case any provision in this Supplemental Indenture or in the Notes shall be invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining provisions shall not in any way be affected or impaired thereby.

Section 1.11. Benefits of Indenture.

Nothing in this Supplemental Indenture or in the Notes, express or implied, shall give to any Person, other than the parties hereto and their successors hereunder and the Holders, any benefit or any legal or equitable right, remedy or claim under this Supplemental Indenture.

Section 1.12. Governing Law.

This Supplemental Indenture and the Notes shall be governed by and construed in accordance with the laws of the State of New York.

Section 1.13. Legal Holidays.

In any case where any Interest Payment Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or the Maturity Date

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of any Note or the last date on which a Holder has the right to convert his Notes shall not be a Business Day, then (notwithstanding any other provision of this Supplemental Indenture or of the Notes) payment of Interest or principal or conversion of the Notes need not be made on such date, but may be made on the next succeeding Business Day with the same force and effect as if made on the Interest Payment Date, Redemption Date, Optional Put Repurchase Date or Fundamental Change Repurchase Date, or at the Maturity Date, or on such last day for conversion; provided that no Interest shall accrue and no principal amount shall accrete for the period from and after such Interest Payment Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or the Maturity Date, as the case may be. Notwithstanding the foregoing, the right to convert a Note shall cease at the close of business on the Scheduled Trading Day immediately preceding the Maturity Date.

Section 1.14. [Reserved].

Section 1.15. Relationship with Base Indenture.

The terms and provisions contained in the Base Indenture shall constitute, and are hereby expressly made, a part of this Supplemental Indenture and the Company and the Trustee, by their execution and delivery of this Supplemental Indenture, expressly agree to such terms and provisions and to be bound thereby. However, to the extent any provision of the Base Indenture conflicts with the express provisions of this Supplemental Indenture, the provisions of this Supplemental Indenture shall govern and be controlling.

The Trustee accepts the amendment of the Base Indenture effected by this Supplemental Indenture and agrees to execute the trust created by the Base Indenture as hereby amended, but only upon the terms and conditions set forth in the Indenture, including the terms and provisions defining and limiting the liabilities and responsibilities of the Trustee in the performance of the trust created by the Base Indenture, and without limiting the generality of the foregoing, the Trustee shall not be responsible in any manner whatsoever for or with respect to any of the recitals or statements contained herein, all of which recitals or statements are made solely by the Company, or for or with respect to (a) the validity or sufficiency of this Supplemental Indenture or any of the terms or provisions hereof, (b) the proper authorization hereof by the Company, (c) the due execution hereof by the Company or (d) the consequences (direct or indirect and whether deliberate or inadvertent) of any amendment herein provided for, and the Trustee makes no representation with respect to any such matters.

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ARTICLE 2

N OTE F ORMS

Section 2.01. Form Generally.

The Notes shall be in substantially the form set forth in this Article 2, with such appropriate insertions, omissions, substitutions and other variations as are required or permitted by this Supplemental Indenture, and may have such letters, numbers or other marks of identification and such legends or endorsements placed thereon as may be required to comply with the rules of any securities exchange, the Code, and regulations thereunder, or as may, consistent herewith, be determined by the officers executing such Notes, as evidenced by their execution thereof. The Company shall furnish any such legends and endorsements to the Trustee in writing. All Notes shall be in fully registered form.

Notices of Conversion shall be in substantially the form set forth in Section 2.03.

The Notes shall be printed, lithographed, typewritten or engraved or produced by any combination of these methods or may be produced in any other manner permitted by the rules of any automated quotation system or securities exchange (including on steel engraved borders if so required by any securities exchange upon which the Notes may be listed) on which the Notes may be listed for trading, as the case may be, all as determined by the officers executing such Notes, as evidenced by their execution thereof.

Section 2.02. Form of Note.

[FORM OF FACE OF NOTE]

The following legend shall appear on the face of each Global Note:

THIS NOTE IS A GLOBAL NOTE WITHIN THE MEANING OF THE SUPPLEMENTAL INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF THE DEPOSITARY OR A NOMINEE OF THE DEPOSITARY, WHICH MAY BE TREATED BY THE COMPANY, THE TRUSTEE AND ANY AGENT THEREOF AS OWNER AND HOLDER OF THIS NOTE FOR ALL PURPOSES.

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER

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NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN DEFINITIVE REGISTERED FORM IN THE LIMITED CIRCUMSTANCES REFERRED TO IN THE SUPPLEMENTAL INDENTURE, THIS GLOBAL NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

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ENERSYS

3.375% Convertible Senior Notes due 2038

CUSIP No. 29275Y AA0

ENERSYS, a corporation duly organized and existing under the laws of the State of Delaware (herein called the “ Company, ” which term includes any successor Person under the Supplemental Indenture referred to on the reverse hereof), for value received, hereby promises to pay to                      [ if this Note is a Global Note , then insert – CEDE & CO.], or registered assigns, the principal sum of [                      UNITED STATES DOLLARS (U.S. $                      )] [ if this Note is a Global Note, then insert — the principal sum as set forth in the “Schedule of Increases or Decreases” attached hereto plus an accreted amount as specified below and in the Supplemental Indenture, which shall not exceed                      UNITED STATES DOLLARS ($              ) except for such accreted amount], on June 1, 2038 (the “ Maturity Date ”), and to pay interest thereon, from May 28, 2008, or from the most recent Interest Payment Date (as defined below) to which interest has been paid or duly provided for, semi-annually in arrears on June 1 and December 1 in each year (each, an “ Interest Payment Date ”), commencing on December 1, 2008 at the rate of 3.375% per annum. The Notes will cease to bear interest (except Contingent Interest, as applicable) on June 1, 2015, and instead from such date the principal amount of the Notes will accrete at a rate that provides Holders with an aggregate annual yield to maturity of 3.375% per year (computed on a semi-annual bond-equivalent basis) as provided in the Supplemental Indenture. The interest so payable, and punctually paid or duly provided for, on any Interest Payment Date shall, as provided in the Indenture, be paid to the Person in whose name this Note (or one or more Predecessor Notes) is registered at the close of business on the Regular Record Date for such interest, which shall be the May 15 or November 15 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Except as otherwise provided in the Supplemental Indenture, any such interest not so punctually paid or duly provided for shall forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Note (or one or more Predecessor Notes) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee pursuant to Section 3.10 of the Supplemental Indenture, notice whereof shall be given to Holders not less than 10 days prior to the Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any automated quotation system or securities exchange on which the Notes may then be listed for trading, and upon such notice as may be required by such exchange, all as more fully provided in the Supplemental Indenture. At the Company’s request, the Trustee shall give any notice required hereunder to be provided to Holders in the Company’s name

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and at the Company’s expense; provided that the text of such notice shall be prepared by the Company. Payments of principal shall be made upon the surrender of this Note by the Holder thereof at the Corporate Trust Office of the Trustee, or at such other office or agency of the Company as may be designated by it for such purpose in such lawful monies of the United States of America as at the time of payment shall be legal tender for the payment of public and private debts, or at such other offices or agencies as the Company may designate. All amounts due in cash with respect to the Notes shall be paid (a) in the case this Note is in global form, by wire transfer of immediately available funds to the account designated by the Depositary or its nominee; (b) in the case this Note is held, other than in global form, by a Holder in an aggregate principal amount of $5.0 million or less, by check mailed to such Holders; and (c) in the case this Note is held, other than in global form, by a Holder in an aggregate principal amount of more than $5.0 million, either by check mailed to such Holder or, upon application by such Holder to the Registrar not later than the relevant Record Date or 15 calendar days prior to such other date on which such amounts are due, by wire transfer in immediately available funds to such Holder’s account within the United States, which application shall remain in effect until the Holder notifies, in writing, the Registrar to the contrary.

Except as specifically provided herein and in the Supplemental Indenture, the Company shall not be required to make any payment with respect to any tax, assessment or other governmental charge imposed by any government or any political subdivision or taxing authority thereof or therein.

Reference is hereby made to the further provisions of this Note set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to on the reverse hereof or an Authenticating Agent by the manual signature of one of their respective authorized signatories, this Note shall not be entitled to any benefit under the Supplemental Indenture or be valid or obligatory for any purpose.

[Remainder of page intentionally left blank]

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IN WITNESS WHEREOF, the Company has caused this Note to be duly executed.

TRUSTEE’S CERTIFICATE OF AUTHENTICATION

This is one of the Notes referred to in the within-mentioned Supplemental Indenture.

Dated:                     

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[FORM OF REVERSE OF NOTE]

ENERSYS

3.375% Convertible Senior Notes due 2038

This Note is one of a duly authorized issue of Notes of the Company designated as its “ 3.375% Convertible Senior Notes due 2038 ” (herein called the “ Notes ”) issued and to be issued under the Indenture (the “ Base Indenture ”), dated as of May 28, 2008, between the Company and The Bank of New York, as Trustee (herein called the “ Trustee, ” which term includes any successor trustee under the Indenture (as defined below)), as supplemented and modified by the First Supplemental Indenture (the “ Supplemental Indenture ” and, together with the Base Indenture, the “ Indenture ”), dated as of May 28, 2008, between the Company and the Trustee, to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee and the Holders of the Notes and of the terms upon which the Notes are, and are to be, authenticated and delivered. As provided in the Supplemental Indenture and subject to certain limitations therein set forth, the Notes are exchangeable for a like aggregate Original Principal Amount of Notes of any authorized denominations as requested by the Holder surrendering the same upon surrender of the Note or Notes to be exchanged, at the Corporate Trust Office of the Trustee. The Trustee upon such surrender by the Holder hereof and the satisfaction of any requirements therefor set forth in the Supplemental Indenture shall issue the new Notes in the requested denominations. Additional Notes may be issued in an unlimited aggregate principal amount, subject to certain conditions specified in the Supplemental Indenture.

No sinking fund is provided for in the Notes.

In any case where any Interest Payment Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or the Maturity Date of any Note or the last date on which a Holder has the right to convert his Notes shall not be a Business Day, then (notwithstanding any other provision of the Supplemental Indenture or of the Notes) payment of Interest or Accreted Principal Amount or conversion of the Notes need not be made on such date, but may be made on the next succeeding Business Day with the same force and effect as if made on the Interest Payment Date, Redemption Date, Optional Put Repurchase Date or Fundamental Change Repurchase Date or at the Maturity Date, or on such last day for conversion, as the case may be; provided that no Interest shall accrue and no principal amount shall accrete for the period from and after such Interest Payment Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or the Maturity Date, as the case may be.

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The Supplemental Indenture contains provisions permitting the Company and the Trustee in certain circumstances, without the consent of the Holders of the Notes, and in other circumstances, with the consent of the Holders of not less than a majority in aggregate Original Principal Amount of the Notes at the time outstanding, evidenced as in the Supplemental Indenture provided, to execute supplemental indentures adding any provisions to or changing in any manner or eliminating any of the provisions of the Supplemental Indenture or of any supplemental indenture or modifying in any manner the rights of the Holders of the Notes; provided , however , that no such supplemental indenture shall make any of the changes set forth in Section 8.02 of the Supplemental Indenture, without the consent of the Holder of each Outstanding Note affected thereby. It is also provided in the Supplemental Indenture that, prior to any declaration accelerating the maturity of the Notes, the Holders of a majority in Original Principal Amount of the Notes at the time Outstanding may on behalf of the Holders of all of the Notes waive any past Default or Event of Default under the Supplemental Indenture and its consequences except as provided in the Supplemental Indenture. Any such consent or waiver by the Holder of this Note (unless revoked as provided in the Supplemental Indenture) shall be conclusive and binding upon such Holder and upon all future holders and owners of this Note and any Notes which may be issued in exchange or substitution hereof, irrespective of whether or not any notation thereof is made upon this Note or such other Notes.

No reference herein to the Supplemental Indenture and no provision of this Note or of the Supplemental Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the Accreted Principal Amount of, and accrued and unpaid Interest on, this Note, at the place, at the respective times, at the rate and in the lawful money herein prescribed.

Subject to the provisions of the Supplemental Indenture, upon the occurrence of a Fundamental Change or on an Optional Put Repurchase Date, the Holder has the right, at such Holder’s option, to require the Company to repurchase all of such Holder’s Notes or any portion thereof (in Original Principal Amounts of $1,000 or integral multiples thereof) on the Fundamental Change Repurchase Date or Optional Put Repurchase Date, as applicable, at a price equal to 100% of the Accreted Principal Amount of the Notes such Holder elects to require the Company to repurchase, together with accrued and unpaid Interest to, but excluding, the Fundamental Change Repurchase Date or Optional Put Repurchase Date, as applicable, unless such Fundamental Change Repurchase Date or Optional Put Repurchase Date, as applicable, falls after a Regular Record Date and on or prior to the corresponding Interest Payment Date, in which case the Company shall pay the full amount of accrued and unpaid Interest payable on such Interest Payment Date to the Holder of record at the close of business on the corresponding Regular Record Date. No later than 20 Business Days prior to each Optional Put Repurchase Date, the Company shall give notice to each Holder (and to beneficial owners as required by applicable law) of their related repurchase

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right. The Company or, at the written request of the Company, the Trustee shall mail to all Holders of record of the Notes a notice of the occurrence of a Fundamental Change and of the repurchase right arising as a result thereof after the occurrence of any Fundamental Change, but on or before the 15th calendar day following such occurrence.

The Holder hereof has the right, at its option, (a) upon the occurrence of certain conditions specified in the Supplemental Indenture, at any time prior to the close of business on the Scheduled Trading Day immediately preceding March 1, 2015, or (b) on or after March 1, 2015, at any time prior to the close of business on the Scheduled Trading Day immediately preceding the Maturity Date, to convert any Notes or portion thereof which is $1,000 in Original Principal Amount or an integral multiple thereof, into a combination of cash and shares of Common Stock (or entirely cash or entirely shares of Common Stock, at the election of the Company, as set forth in Section 12.02 of the Supplemental Indenture) or Reference Property, in each case at the Conversion Rate specified in the Supplemental Indenture, as adjusted from time to time as provided in the Supplemental Indenture, upon satisfaction of certain requirements set forth in the Supplemental Indenture, including, if applicable, the surrender of this Note, together with a Notice of Conversion, a form of which is contained under Section 2.03 of the Supplemental Indenture, as provided in the Supplemental Indenture and this Note, to the Conversion Agent, and, unless the shares of Common Stock or Reference Property, as the case may be, issuable on conversion are to be issued in the same name as this Note, duly endorsed by, or accompanied by instruments of transfer in form satisfactory to the Company duly executed by, the Holder or by his duly authorized attorney. The initial Conversion Rate shall be 24.6305 shares of Common Stock for each $1,000 in Original Principal Amount of Notes. No fractional shares of Common Stock or Reference Property, as the case may be, shall be issued upon any conversion, but an adjustment in cash shall be paid to the Holder, as provided in the Supplemental Indenture, in respect of any fraction of such share which would otherwise be issuable upon the surrender of any Note or Notes for conversion. No adjustment shall be made for dividends or any such shares issued upon conversion of such Notes except as provided in the Supplemental Indenture.

Upon due presentment for registration of transfer of this Note at the office or agency of the Company, a new Note or Notes of authorized denominations for an equal aggregate Original Principal Amount shall be issued to the transferee in exchange thereof, subject to the limitations provided in the Supplemental Indenture, without charge except for any tax, assessments or other governmental charge imposed in connection therewith.

The Company, the Trustee, any Authenticating Agent, any Paying Agent, any Conversion Agent and any Registrar may deem and treat the registered Holder hereof as the absolute owner of this Note (whether or not this Note shall

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be overdue and notwithstanding any notation of ownership or other writing hereon), for the purpose of receiving payment hereof, or on account hereof, for the conversion hereof and for all other purposes, and neither the Company nor the Trustee nor any other authenticating agent nor any Paying Agent nor any other Conversion Agent nor any Registrar shall be affected by any notice to the contrary. All payments made to or upon the order of such registered Holder shall, to the extent of the sum or sums paid, satisfy and discharge liability for monies payable on this Note.

No recourse for the payment of the Accreted Principal Amount of, or accrued and unpaid Interest on, this Note, or for any claim based hereon or otherwise in respect hereof, and no recourse under or upon any obligation, covenant or agreement of the Company in the Supplemental Indenture or any indenture supplemental thereto or in any Note, or because of the creation of any Indebtedness represented thereby, shall be had against any incorporator, stockholder, employee, agent, officer, director or Subsidiary, as such, past, present or future, of the Company or of any successor corporation, either directly or through the Company or any successor corporation, whether by virtue of any constitution, statute or rule of law or by the enforcement of any assessment or penalty or otherwise, all such liability being, by the acceptance hereof and as part of the consideration for the issue hereof, expressly waived and released.

Terms used in this Note and defined in the Supplemental Indenture are used herein as therein defined.

In the case of any conflict between the provisions of this Note and the Indenture, the provisions of the Indenture shall control.

The Indenture and this Note shall be governed by and construed in accordance with the laws of the State of New York.

Customary abbreviations may be used in the name of a Holder or an assignee, such as TEN COM (=tenants in common), TENANT (=tenants by the entireties), JT TEN (joint tenants with right of survivorship and not as tenants in common), CUST (=custodian), and U/G/M/A (=Uniform gift to Minors Act).

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[TO BE INCLUDED IN GLOBAL NOTES]

SCHEDULE OF INCREASES OR DECREASES

The initial Original Principal Amount of this Note is                      UNITED STATES DOLLARS ($                      ). The following increases or decreases in a part of this Note have been made:

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FORM OF OPTIONAL PUT REPURCHASE NOTICE AND FUNDAMENTAL CHANGE REPURCHASE NOTICE

To: EnerSys

The undersigned registered owner of this Note hereby acknowledges receipt of a notice from EnerSys (the “ Company ”) as to the occurrence of (check the appropriate box):

and hereby directs the Company to pay, or cause the Trustee to pay, it or                      an amount in cash equal to 100% of the Accreted Principal Amount, or the portion thereof (which is $1,000 in Original Principal Amount or an integral multiple thereof) below designated, to be repurchased plus interest accrued to, but excluding, the Optional Put Repurchase Date or the Fundamental Change Repurchase Date, as applicable, except as provided in the Supplemental Indenture.

Dated:

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Section 2.03. Form of Notice of Conversion.

NOTICE OF CONVERSION

The undersigned Holder of this Note hereby irrevocably exercises the option to convert this Note, or any portion of the Accreted Principal Amount hereof (which is U.S. $1,000 Original Principal Amount or an integral multiple of U.S. $1,000 in excess thereof; provided that the unconverted portion of such Original Principal Amount is U.S. $1,000 or any integral multiple of U.S. $1,000 in excess thereof) below designated, into a combination of cash and shares of Common Stock (or, at the election of the Company, entirely cash or entirely shares of Common Stock) or Reference Property in accordance with the terms of the Supplemental Indenture referred to in this Note, and directs that the consideration due upon such conversion (including a check in payment for any fractional share and any Notes representing any unconverted principal amount hereof), be delivered to and be registered in the name of the undersigned unless a different name has been indicated below. If shares of Common Stock, Reference Property or Notes are to be registered in the name of a Person other than the undersigned, (a) the undersigned shall pay all transfer taxes payable with respect thereto and (b) the signature(s) must be guaranteed by an Eligible Guarantor Institution with membership in an approved signature guarantee program pursuant to Rule 17Ad-15 under the Securities Exchange Act of 1934. Any amount required to be paid by the undersigned on account of interest accompanies this Note.

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If only a portion of the Notes is to be converted, please indicate:

Amount: U.S. $                  Denominations: U.S. $                 

(U.S. $1,000 Original Principal Amount or any integral multiple of U.S. $1,000 in excess thereof, provided that the unconverted portion of such principal amount is U.S. $1,000 Original Principal Amount or any integral multiple of U.S. $1,000 in excess thereof).

Section 2.04. Form of Assignment.

ASSIGNMENT

For value received,                      hereby sell(s), assign(s) and transfer(s) unto                      (Please insert Social Security or other identifying number of assignee) the within note, and hereby irrevocably constitutes and appoints                                          as attorney to transfer the said note on the books of the Company, with full power of substitution in the premises.

Signature(s) must be guaranteed by an Eligible Guarantor Institution with membership in an approved signature guarantee program pursuant to Rule 17Ad-15 under the Securities Exchange Act of 1934.

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ARTICLE 3

T HE N OTES

Section 3.01. Title and Terms.

(a) The Notes shall be known and designated as the “ 3.375% Convertible Senior Notes due 2038 ” of the Company. Their Maturity Date shall be June 1, 2038 and they shall bear Regular Interest on the Original Principal Amount in accordance with Section 3.02.

(b) Beginning with the six-month period commencing on June 1, 2015, Contingent Interest shall be paid, if applicable, in accordance with Section 3.03.

(c) Commencing on June 1, 2015, the Accreted Principal Amount shall increase in accordance with Section 3.04.

(d) The Company shall pay Interest on overdue Accreted Principal Amount at the rate borne by the Notes, and it shall pay Interest on overdue installments of Interest at the same rate, in each case to the extent lawful.

(e) The Notes shall be subject to repurchase by the Company at the option of the Holders as provided in Section 11.08 and Section 11.09 hereof.

(f) The Accreted Principal Amount of and Interest on the Notes shall be payable as provided in the form of Notes set forth in Section 2.02. The Optional Put Repurchase Price or the Fundamental Change Repurchase Price, as applicable, shall be payable at such place as is identified in the Optional Put Repurchase Notice or the Fundamental Change Repurchase Right Notice, as applicable, given pursuant to Section 11.08 and Section 11.09, respectively.

(g) The Notes shall be general senior unsecured obligations of the Company and shall rank pari passu with all of the Company’s other general senior unsecured obligations.

(h) The Notes may be redeemed at the option of the Company prior to Maturity pursuant to Section 11.01 hereof.

(i) The Notes shall be convertible as provided in Article 12.

(j) Article XII of the Base Indenture shall not be applicable to the Notes.

Section 3.02. Regular Interest.

Subject to the last paragraph of Section 3.10, Regular Interest will accrue on the Notes at the rate of 3.375% per year (“ Regular Interest ”) during any six-month period from and including June 1 to and including November 30 or from

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and including December 1 to and including May 31 (each, an “ Interest Period ”), commencing on December 1, 2008; provided that the initial Interest Period shall commence on May 28, 2008 and run to and including November 30, 2008. Regular Interest will be payable semi-annually in arrears on each Interest Payment Date (subject to Section 1.13) to the Holder of record at the close of business on the Regular Record Date preceding such Interest Payment Date; provided that the Notes will cease to accrue Regular Interest as of June 1, 2015.

Section 3.03. Contingent Interest.

(a) The Company will pay Contingent Interest in cash to Holders during any Interest Period beginning with the six-month Interest Period commencing on June 1, 2015, during any Interest Period if the Trading Price of the Notes for each of the five Trading Days ending on, and including, the second Trading Day immediately preceding the first day of the applicable Interest Period (as used in this Section 3.03, the “ Measurement Period ”) equals or exceeds 130% of the Accreted Principal Amount of the Notes as of such Trading Day.

(b) During any Interest Period when Contingent Interest shall be payable with respect to the Notes, the Contingent Interest payable per $1,000 in Original Principal Amount of Notes will equal 0.40% of the average Trading Price of $1,000 in Original Principal Amount of the Notes for the applicable Measurement Period.

(c) The Company will promptly (and in any event prior to the applicable Interest Payment Date) notify Holders upon determination that they will be entitled to receive Contingent Interest during an Interest Period.

(d) The Company shall pay Contingent Interest owed pursuant to this Section 3.03 for any Interest Period on the Interest Payment Date immediately succeeding the applicable Interest Period, to Holders of the Notes as of the Regular Record Date related to such Interest Payment Date.

Section 3.04. Accretion.

Commencing on June 1, 2015, the Original Principal Amount shall accrete at a rate that provides Holders with an aggregate annual yield to Maturity of 3.375% per annum (computed on a semi-annual bond-equivalent yield basis). Schedule B hereto sets forth the Accreted Principal Amounts as of specified dates during the period from June 1, 2015 through the Maturity Date.

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Section 3.05. Denominations.

The Notes shall be issuable only in registered form, without coupons, in denominations of U.S. $1,000 of Original Principal Amount and integral multiples of U.S. $1,000 in excess thereof.

Section 3.06. Execution, Authentication, Delivery and Dating.

The Notes shall be executed on behalf of the Company by its Chief Executive Officer, its President or one of its Vice Presidents, attested by its Secretary or one of its Assistant Secretaries. The signature of any of these officers on the Notes may be manual or facsimile.

Notes bearing the manual or facsimile signatures of individuals who were at any time the proper officers of the Company shall bind the Company, notwithstanding that such individuals or any of them have ceased to hold such offices prior to the authentication and delivery of such Notes or did not hold such offices at the date of such Notes.

At any time and from time to time after the execution and delivery of this Supplemental Indenture, the Company may deliver Notes executed by the Company to the Trustee for authentication, together with a Company Order for the authentication and delivery of such Notes; and the Trustee in accordance with such Company Order shall authenticate and deliver such Notes as provided in this Indenture and not otherwise.

Each Note shall be dated the date of its authentication.

No Note shall be entitled to any benefit under this Supplemental Indenture or be valid or obligatory for any purpose unless there appears on such Note a certificate of authentication substantially in the form provided for herein executed by the Trustee by manual signature, and such certificate upon any Note shall be conclusive evidence, and the only evidence, that such Note has been duly authenticated and delivered hereunder.

Section 3.07. Global Notes; Non-Global Notes; Book-Entry Provisions.

(a) Global Notes

(i) Each Global Note issued and authenticated under this Supplemental Indenture shall be registered in the name of the Depositary designated by the Company for such Global Note or a nominee thereof and delivered to such Depositary or a nominee thereof or custodian therefor, and each such Global Note shall constitute a single Note for all purposes of this Indenture. The Company hereby appoints DTC as the initial Depositary.

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(ii) Except for exchanges of Global Notes for definitive, non-Global Notes at the sole discretion of the Company, no Global Note may be exchanged in whole or in part for Notes registered, and no transfer of a Global Note in whole or in part may be registered, in the name of any Person other than the Depositary for such Global Note or a nominee thereof unless (A) such Depositary (1) has notified the Company that it is unwilling or unable to continue as Depositary for such Global Note, or (2) has ceased to be a clearing agency registered as such under the Exchange Act, has ceased to be a “clearing corporation” within the meaning of the Uniform Commercial Code, or announces an intention permanently to cease business or does in fact do so or (B) there shall have occurred and be continuing an Event of Default with respect to such Global Note and the maturity of the Notes shall have been accelerated in accordance with Section 5.02 and any Holder shall have given written notice to the Company requesting the issuance of definitive Notes. In such event set forth in clause (A) above, if a successor Depositary for such Global Note is not appointed by the Company within 90 calendar days after the Company receives such notice or becomes aware of such ineligibility, the Company shall execute, and the Trustee, upon receipt of a Company Order directing the authentication and delivery of Notes, shall authenticate and deliver, Notes, in any authorized denominations in an aggregate principal amount equal to the Accreted Principal Amount of such Global Note in exchange for such Global Note.

(iii) If any Global Note is to be exchanged for other Notes or canceled in whole, it shall be surrendered by or on behalf of the Depositary or its nominee to the Trustee, as Registrar, for exchange or cancellation, as provided in this Article 3. If any Global Note is to be exchanged for other Notes or canceled in part, or if another Note is to be exchanged in whole or in part for a beneficial interest in any Global Note, in each case as provided in this Article 3, then either (A) such Global Note shall be so surrendered for exchange or cancellation, as provided in this Article 3, or (B) the Original Principal Amount thereof shall be reduced or increased by an amount equal to the portion thereof to be so exchanged or canceled, or equal to the principal amount of such other Note to be so exchanged for a beneficial interest therein, as the case may be, by means of an appropriate adjustment made on the records of the Trustee, as Registrar, whereupon the Trustee, in accordance with the Applicable Procedures, shall instruct the Depositary or its authorized representative to make a corresponding adjustment to its records. Upon any such surrender or adjustment of a Global Note, the Trustee shall, upon receipt of a Company Order, subject to this Article 3, authenticate and deliver any Notes issuable in exchange for such Global Note (or any portion thereof) to or upon the order of, and registered in such names as may be directed

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by, the Depositary or its authorized representative. The Trustee shall be entitled to receive from the Depositary the names, addresses and tax identification numbers of the Persons in whose names the Notes are to be registered prior to such authentication and delivery. Upon the request of the Trustee in connection with the occurrence of any of the events specified in the preceding paragraph, the Company shall promptly make available to the Trustee a reasonable supply of Notes that are not in the form of Global Notes. The Trustee shall be entitled to rely upon any order, direction or request of the Depositary or its authorized representative which is given or made pursuant to this Article 3 if such order, direction or request is given or made in accordance with the Applicable Procedures.

(iv) Every Note authenticated and delivered upon registration of transfer of, or in exchange for or in lieu of, a Global Note or any portion thereof, whether pursuant to this Article 3 or otherwise, shall be authenticated and delivered in the form of, and shall be, a registered Global Note, unless such Note is to be registered in accordance with this Article 3 in the name of a Person other than the Depositary for such Global Note or a nominee thereof, in which case such Note shall be authenticated and delivered in definitive, fully registered form, without interest coupons.

(v) The Depositary or its nominee, as registered owner of a Global Note, shall be the Holder of such Global Note for all purposes under this Supplemental Indenture and the Notes, and owners of beneficial interests in a Global Note shall hold such interests pursuant to the Applicable Procedures. Accordingly, any such owner’s beneficial interest in a Global Note shall be shown only on, and the transfer of such interest shall be effected only through, records maintained by the Depositary or its nominee or its Agent Members and such owners of beneficial interests in a Global Note shall not be considered the owners or holders thereof.

(b) Non-Global Notes. Notes issued pursuant to Section 3.07(a)(ii) shall be in definitive, fully registered form, without interest coupons.

Section 3.08. Persons Deemed Owners.

Prior to due presentment of a Note for registration of transfer, the Company, the Trustee, any Paying Agent and any agent of the Company, the Trustee or any Paying Agent may treat the Person in whose name such Note is registered as the owner of such Note for the purpose of receiving payment of principal of and (subject to Section 3.10) Interest on such Note and for all other purposes whatsoever, whether or not such Note be overdue, and neither the Company, the Trustee, any Paying Agent nor any agent of the Company, the Trustee or any Paying Agent shall be affected by notice to the contrary.

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Section 3.09. Mutilated, Destroyed, Lost and Stolen Notes.

If any mutilated Note is surrendered to the Trustee, the Company shall execute and upon receipt of a Company Order, the Trustee shall authenticate and deliver in exchange therefor a new Note of like tenor and Original Principal Amount and bearing a number not contemporaneously Outstanding.

If there shall be delivered to the Company and the Trustee (a) evidence to their satisfaction of the destruction, loss or theft of any Note and (b) such security or indemnity as may be required by them to save each of them and any agent of either of them harmless, then, in the absence of notice to the Company or the Trustee that such Note has been acquired by a bona fide purchaser, the Company shall execute and upon receipt of a Company Order, the Trustee shall authenticate and deliver, in lieu of any such destroyed, lost or stolen Note, a new Note of like tenor and principal amount and bearing a number not contemporaneously Outstanding.

Upon the issuance of any new Note under this Section 3.09, the Company may require the payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in relation thereto and any other expenses (including the fees and expenses of the Trustee) connected therewith.

Every new Note issued pursuant to this Section 3.09 in lieu of any destroyed, lost or stolen Note shall constitute an original additional contractual obligation of the Company, whether or not the destroyed, lost or stolen Note shall be at any time enforceable by anyone, and shall be entitled to all the benefits of this Supplemental Indenture equally and proportionately with any and all other Notes duly issued hereunder.

The provisions of this Section 3.09 are exclusive and shall preclude (to the extent lawful) all other rights and remedies with respect to the replacement or payment of mutilated, destroyed, lost or stolen Notes.

Section 3.10. Payment of Interest; Interest Rights Preserved.

Interest on any Note which is payable, and is punctually paid or duly provided for, on any Interest Payment Date shall be paid to the Person in whose name that Note (or one or more Predecessor Notes) is registered at the close of business on the Regular Record Date for such Interest.

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Any Interest on any Note which is payable, but is not punctually paid or duly provided for, on any Interest Payment Date (herein called “ Defaulted Interest ”) shall forthwith cease to be payable to the Holder on the relevant Regular Record Date by virtue of having been such Holder, and such Defaulted Interest may be paid by the Company, at its election in each case, as provided in clause (a) or (b) below:

(a) The Company may elect to make payment of any Defaulted Interest to the Persons in whose names the Notes (or their respective Predecessor Notes) are registered at the close of business on a special record date for the payment of such Defaulted Interest (a “ Special Record Date ”), which shall be fixed in the following manner. The Company shall notify the Trustee in writing of the amount of Defaulted Interest proposed to be paid on each Note and the date of the proposed payment, and at the same time the Company shall deposit with the Trustee an amount of money equal to the aggregate amount proposed to be paid in respect of such Defaulted Interest or shall make arrangements reasonably satisfactory to the Trustee for such deposit prior to the date of the proposed payment, such money when deposited to be held in trust for the benefit of the Persons entitled to such Defaulted Interest as in this clause provided. Thereupon the Trustee shall fix a Special Record Date for the payment of such Defaulted Interest which shall be not more than 15 days and not less than 10 days prior to the date of the proposed payment and not less than 10 days after the receipt by the Trustee of the notice of the proposed payment. The Trustee shall promptly notify the Company of such Special Record Date and, in the name and at the expense of the Company, shall cause notice of the proposed payment of such Defaulted Interest and the Special Record Date therefor to be mailed, first-class postage prepaid, to each Holder at his address as it appears in the Securities Register, not less than 10 days prior to such Special Record Date. Notice of the proposed payment of such Defaulted Interest and the Special Record Date therefor having been so mailed, such Defaulted Interest shall be paid to the Persons in whose names the Notes (or their respective Predecessor Notes) are registered at the close of business on such Special Record Date and shall no longer be payable pursuant to the following clause (b).

(b) The Company may make payment of any Defaulted Interest in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Notes may be listed, and upon such notice as may be required by such exchange, if, after notice given by the Company to the Trustee of the proposed payment pursuant to this clause, such manner of payment shall be deemed practicable by the Trustee.

Subject to the foregoing provisions of this Section 3.10, each Note delivered under this Supplemental Indenture upon registration of transfer of or in exchange for or in lieu of any other Note shall carry the rights to Interest accrued and unpaid, and to accrue, which were carried by such other Note, as provided for in this Indenture and the Notes.

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Section 3.11. Cancellation.

All Notes surrendered for payment, registration of transfer or exchange or conversion shall, if surrendered to any Person other than the Trustee, be delivered to the Trustee and shall be promptly cancelled by it. The Company may at any time deliver to the Trustee for cancellation any Notes previously authenticated and delivered hereunder which the Company may have acquired in any manner whatsoever, and all Notes so delivered shall be promptly cancelled by the Trustee. No Notes shall be authenticated in lieu of or in exchange for any Notes cancelled as provided in this Section 3.11, except as expressly permitted by this Supplemental Indenture. All cancelled Notes held by the Trustee shall be disposed of as directed by a Company Order.

Section 3.12. Computation of Interest.

Interest on the Notes shall be computed on the basis of a 360-day year of twelve 30-day months.

ARTICLE 4

D ISCHARGE

Section 4.01. Discharge of Liability on Notes.

When (a) the Company shall deliver to the Registrar for cancellation all Notes then Outstanding not theretofore delivered to the Registrar for cancellation or (b) all the Notes then Outstanding not theretofore delivered to the Registrar for cancellation shall have (i) been deposited for conversion and the Company shall deliver to the Holders a combination of cash and shares of Common Stock (or, at the election of the Company, entirely cash or entirely shares of Common Stock) sufficient to pay all amounts owing in respect of all such Notes or (ii) become due and payable on the Maturity Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or otherwise, and the Company shall deposit with the Trustee cash sufficient to pay all amounts owing in respect of all such Notes, including the Accreted Principal Amount and Interest accrued and unpaid to the Maturity Date, Redemption Date, Optional Put Repurchase Date, Fundamental Change Repurchase Date or other such date, and if in either case of clauses (a) or (b) above, no Event of Default set forth in Section 5.01(i) or (j) hereof or event (including resulting from such deposit) that, with lapse of time or notice or both, would become an Event of Default set forth in Section 5.01(i) or (j) hereof with respect to the Notes shall have occurred and be continuing, and the Company shall also pay or cause to be paid all other sums payable hereunder by the Company, then this Supplemental Indenture with respect to the Notes shall cease to be of further effect (except as to (x) remaining rights of registration of transfer, substitution and exchange and conversion of Notes, (y) rights hereunder of Holders to receive from the Trustee payments of the amounts then due, including Interest with respect to the Notes and the other rights, duties and

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obligations of Holders, as beneficiaries hereof solely with respect to the amounts, if any, so deposited with the Trustee and (z) the rights, obligations and immunities of the Trustee, Authenticating Agent, Paying Agent, Conversion Agent and Registrar under this Supplemental Indenture with respect to the Notes), and the Trustee, on demand of the Company accompanied by an Officers’ Certificate and an Opinion of Counsel as required by Section 4.03 and at the cost and expense of the Company, shall execute proper instruments acknowledging satisfaction of and discharging this Supplemental Indenture with respect to the Notes; provided , however , the Company hereby agrees to reimburse the Trustee, Authenticating Agent, Paying Agent, Conversion Agent and Registrar for any costs or expenses thereafter reasonably and properly incurred by the Trustee, Authenticating Agent, Paying Agent, Conversion Agent and Registrar and to compensate the Trustee, Authenticating Agent, Paying Agent, Conversion Agent and Registrar for any services thereafter reasonably and properly rendered by the Trustee, Authenticating Agent, Paying Agent, Conversion Agent and Registrar in connection with this Indenture with respect to the Notes.

Section 4.02. Reinstatement.

If the Trustee or the Paying Agent is unable to apply any money to the Holders entitled thereto by reason of any order or judgment of any court of governmental authority enjoining, restraining or otherwise prohibiting such application, the Company’s obligations under this Supplemental Indenture with respect to the Notes shall be revived and reinstated as though no discharge of liability on the Notes had occurred pursuant to Section 4.01 until such time as the Trustee or the Paying Agent is permitted to apply all such money in accordance with this Supplemental Indenture and the Notes to the Holders entitled thereto; provided , however , that if the Company makes any payment of the Accreted Principal Amount of or Interest on any Note following the reinstatement of its obligations, the Company shall be subrogated to the rights of the Holders of such Notes to receive such payment from the money held by the Trustee or Paying Agent.

Section 4.03. Officers’ Certificate; Opinion of Counsel.

Upon any application or demand by the Company to the Trustee to take any action under Section 4.01, the Company shall furnish to the Trustee an Officers’ Certificate and Opinion of Counsel stating that all conditions precedent, if any, provided for in this Supplemental Indenture relating to the proposed action have been complied with.

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ARTICLE 5

R EMEDIES

Section 5.01. Events of Default.

“ Event of Default, ” wherever used herein, means any one of the following events with respect to the Notes (whatever the reason for such Event of Default or whether it shall be voluntary or involuntary or be effected by operation of law or pursuant to any judgment, decree or order of any court or any order, rule or regulation of any administrative or governmental body):

(a) default in any payment of Interest on any Note when due and payable and the default continues for a period of 30 days;

(b) default in the payment of Accreted Principal Amount of any Note when due and payable at Maturity, upon required repurchase, upon redemption, upon acceleration or otherwise;

(c) failure by the Company to comply with its obligation to convert