Exhibit 10.1

THE OPTION IDENTIFIED HEREIN AND ANY SHARES ISSUABLE UPON EXERCISE THEREOF HAVE
NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE
SOLD, TRANSFERRED, ASSIGNED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED
UNDER SUCH ACT, OR UNLESS TRMI HOLDINGS INC. ("TRMI-H") HAS RECEIVED AN OPINION
OF COUNSEL OR OTHER EVIDENCE SATISFACTORY TO TRMI-H AND ITS COUNSEL TO THE
EFFECT THAT SUCH REGISTRATION IS NOT REQUIRED.


                                OPTION AGREEMENT


     This Option Agreement ("Agreement") is entered into by and among Ovonic
Battery Company, Inc. ("OBC"), Energy Conversion Devices, Inc. ("ECD") and TRMI
Holdings Inc. ("TRMI-H") as of December 2, 2004.

                              W I T N E S S E T H:

      WHEREAS, TRMI-H is the owner of 4,376,633 shares (the "Shares") of the
outstanding common stock, par value $0.01 per share (the "Common Stock"), of ECD
under that certain Stock Purchase Agreement, dated May 1, 2000 (the "SPA")
between ECD and TRMI-H; and

      WHEREAS, ECD, TRMI-H, ChevronTexaco Technology Ventures LLC, f/k/a Texaco
Energy Systems LLC, f/k/a Texaco Energy Systems Inc. ("CTTV"), OBC, COBASYS LLC
("COBASYS") and Texaco Ovonic Hydrogen Systems LLC ("TOHS") are parties to that
certain Master Agreement dated as of December 2, 2004 (the "Master Agreement");
and

      WHEREAS, the execution and delivery of this Agreement by OBC, ECD and
TRMI-H is a condition precedent to the closing of the transactions contemplated
by the Master Agreement;

      NOW THEREFORE, in consideration of the premises, OBC, ECD and TRMI-H
hereby agree as follows:

      1. Grant of Option. In consideration of the contribution of intellectual
         ---------------
property and related market rights and amendments to the operating agreement of
COBASYS, TRMI-H hereby grants to OBC and its permitted assigns as set forth in
this Agreement, as optionee ("Optionee"), an irrevocable option (the "Option")
to purchase all, or any portion, of the Shares, at a purchase price of per share
(the "Exercise Price") equal to $4.55, and otherwise on the terms and subject to
the conditions set forth in this Agreement. The number of shares of Common Stock
subject to the Option and the Exercise Price shall be subject to adjustment as
provided in Section 10 below.

                                       1

<PAGE>

      2. Term. The Option shall be exercisable from the date of this Agreement
         ----
until November 1, 2005 (the "Termination Date").

      3. Exercise of Option. (a) In order to exercise all or any portion of the
         ------------------
Option, Optionee shall deliver to TRMI-H a Notice of Option Exercise and Stock
Purchase Agreement substantially in the form attached hereto as Exhibit A (the
"Notice of Option Exercise") which shall in no case be for an amount less than
250,000 shares of Common Stock. The Notice of Option Exercise shall be delivered
to TRMI-H in accordance with Section 10(b) of this Agreement no fewer than three
(3) and no more than ten (10) business days prior to the Closing Date (as such
term is defined in the Notice of Option Exercise). Any sale of Common Stock
pursuant to the Option shall be subject to the terms and conditions of this
Agreement and the Notice of Option Exercise. The parties hereby agree that in
the event the Optionee that delivers the Notice of Option Exercise to TRMI-H is
not OBC or an affiliate of OBC, at the Closing (as such term is defined in the
Notice of Option Exercise) (i) TRMI-H will deliver to ECD the stock
certificate(s) representing the shares of Common Stock subject to the Option and
(ii) ECD will deliver to Optionee one or more newly issued stock certificates
representing the Common Stock sold pursuant to the Notice of Option Exercise.
Unless the shares of Common Stock sold pursuant to the Notice of Option Exercise
are included in a registration statement that has been declared effective by the
Securities and Exchange Commission (the "Commission"), each such stock
certificate shall bear a legend in substantially the following form:

      THE SHARES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, TRANSFERRED,
      ASSIGNED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER SUCH
      ACT, OR UNLESS THE ISSUER AND TRMI HOLDINGS INC. ("TRMI-H") HAVE EACH
      RECEIVED AN OPINION OF COUNSEL OR OTHER EVIDENCE SATISFACTORY TO EACH OF
      THE ISSUER AND TRMI-H AND THEIR RESPECTIVE COUNSEL TO THE EFFECT THAT SUCH
      REGISTRATION IS NOT REQUIRED.

      (b) ECD agrees that in connection with any exercise of the Option by any
person other than OBC or an affiliate of OBC, it will grant such Optionee an
opportunity to ask questions and receive answers from ECD regarding the
business, properties, prospects and financial condition of ECD.

      (c) To facilitate the exercise of the Option and/or the sale of any of the
Shares following the Termination Date, TRMI-H hereby requests a Stock
Registration (as such term is defined in the SPA) to permit the public sale of
the Shares from time to time following the effectiveness of the registration
statement, all as contemplated by Rule 415 of Regulation C promulgated by the
Commission. ECD hereby waives its rights under Section 4.3(f) of the SPA with
respect to any public sale of the Shares (including any sale pursuant to Rule
144 of the Commission). TRMI-H agrees that ECD may delay the filing of a
registration statement pursuant to the foregoing request until May 31, 2005.
TRMI-H further agrees that, to the extent permitted by the rules and regulations
of the Commission, the registration statement filed by ECD pursuant


                                       2

<PAGE>

to the foregoing request may include the Option as an additional security
registered thereunder and may register, or be amended to register, the resale of
the Shares by permitted assigns of the Option.

      4. Agreement Not to Sell Common Stock. From the date of this Agreement
         ----------------------------------
until the Termination Date, TRMI-H agrees that it shall not pledge, sell,
contract to sell, sell any option or contract to purchase, purchase any option
or contract to sell, grant any option, right or warrant to purchase, lend, or
otherwise transfer or dispose of, directly or indirectly, any Common Stock or
any securities convertible into or exercisable or exchangeable for Common Stock,
or enter into any swap or other arrangement that transfers to another, in whole
or in part, any of the economic consequences of ownership of Common Stock,
whether any such transaction is to be settled by delivery of Common Stock or
other securities, in cash or otherwise, except pursuant to the Option.

      5. Conditions to Option Exercise. Optionee's right to exercise the Option
         -----------------------------
shall be subject to the condition precedent that Optionee shall deliver or cause
to be delivered to TRMI-H:

           (a)  in the event Optionee is OBC or an affiliate of OBC, an opinion
      dated the Closing Date to the effect that such exercise by Optionee is
      lawful and results in a valid and binding obligation of Optionee,
      enforceable in accordance with its terms, such opinion to be (i) in
      substantially the form set forth in Exhibit B and (ii) issued by Baker &
      McKenzie LLP or other counsel reasonably satisfactory to TRMI-H and
      Optionee; and

           (b)  in the event Optionee is not OBC or an affiliate of OBC, a duly
      executed Representation Certificate substantially in the form attached
      hereto as Exhibit C dated the Closing Date.

      6. Failure to Exercise Option in Full Prior to Termination Date. In the
         ------------------------------------------------------------
event that, by the Termination Date:

           (a)  the Option shall not have been exercised in full for all the
      Shares;

           (b)  a registration statement under the Securities Act of 1933, as
      amended (the "Securities Act"), to permit TRMI-H to make a public offering
      of all of the shares of Common Stock held by it has not been declared
      effective by the Commission and/or is not then in effect; and

           (c)  TRMI-H is otherwise unable to effect an immediate public sale of
      the Shares in full without violation of any applicable law; then, in such
      event, the provisions of Part 4 of the SPA shall be of no further force or
      effect.

      7. Representations of ECD. ECD represents to TRMI-H:
         ----------------------

           (a)  Organization. ECD is a corporation duly organized and validly
      existing under the laws of the State of Delaware. ECD has the full power
      and authority to execute, deliver and perform its obligations under this
      Agreement.


                                       3

<PAGE>

           (b)  Authority. The execution and delivery of this Agreement by ECD,
      and the consummation of the transactions contemplated hereby, have been
      duly authorized by all requisite action on the part of ECD.

           (c)  Enforceability. This Agreement constitutes the legal, valid and
      binding obligation of ECD, enforceable against ECD in accordance with its
      terms, subject to applicable bankruptcy, insolvency, reorganization,
      moratorium and other similar laws affecting creditors' rights generally
      and to the principles of equity (whether enforcement is sought in a
      proceeding in equity or at law).

           (d)  No Conflicts. Neither the execution nor delivery of this
      Agreement, nor the consummation of the transactions contemplated hereby by
      ECD will violate, require a consent, or cause a default under any
      agreement to which ECD is a party. No consent, approval or filing with any
      Governmental Body is required to authorize the execution and delivery of
      this Agreement by ECD or ECD's performance of the terms of this Agreement.

           (e)  Litigation. There is no action, suit, proceeding, claim or
      investigation by any person, entity, administrative agency or Governmental
      Body pending or, to the knowledge of ECD, threatened, against ECD that
      impedes or is likely to impede ECD's ability to consummate the
      transactions contemplated by this Agreement.

      8. Representations of OBC. OBC represents to TRMI-H:
         ----------------------

           (a)  Organization. OBC is a corporation duly organized and validly
      existing under the laws of the State of Delaware. OBC has the full power
      and authority to execute, deliver and perform its obligations under this
      Agreement.

           (b)  Authority. The execution and delivery of this Agreement by OBC,
      and the consummation of the transactions contemplated hereby, have been
      duly authorized by all requisite action on the part of OBC.

           (c)  Enforceability. This Agreement constitutes the legal, valid and
      binding obligation of OBC, enforceable against OBC in accordance with its
      terms, subject to applicable bankruptcy, insolvency, reorganization,
      moratorium and other similar laws affecting creditors' rights generally
      and to the principles of equity (whether enforcement is sought in a
      proceeding in equity or at law).

           (d)  No Conflicts. Neither the execution nor delivery of this
      Agreement, nor the consummation of the transactions contemplated hereby by
      OBC will violate, require a consent, or cause a default under any
      agreement to which OBC is a party. No consent, approval or filing with any
      Governmental Body is required to authorize the execution and delivery of
      this Agreement by OBC or OBC's performance of the terms of this Agreement.


                                       4

<PAGE>

           (e)  Litigation. There is no action, suit, proceeding, claim or
      investigation by any person, entity, administrative agency or Governmental
      Body pending or, to the knowledge of OBC, threatened, against OBC that
      impedes or is likely to impede OBC's ability to consummate the
      transactions contemplated by this Agreement.

      9. Representations of TRMI-H. TRMI-H represents to ECD and OBC as follows:
         -------------------------

           (a)  Organization. TRMI-H is a corporation duly organized and validly
      existing under the laws of the State of Delaware. TRMI-H has the full
      power and authority to execute, deliver and perform its obligations under
      this Agreement.

           (b)  Authority. The execution and delivery of this Agreement by
      TRMI-H and the consummation of the transactions contemplated hereby have
      been duly authorized by all requisite action on the part of TRMI-H.

           (c)  Enforceability. This Agreement constitutes the legal, valid and
      binding obligation of TRMI-H, enforceable against TRMI-H in accordance
      with its terms, subject to applicable bankruptcy, insolvency,
      reorganization, moratorium and other similar laws affecting creditors'
      rights generally and to the principles of equity (whether enforcement is
      sought in a proceeding in equity or at law).

           (d)  No Conflicts. Neither the execution nor delivery of this
      Agreement nor the consummation of the transactions contemplated hereby by
      TRMI-H will violate, require a consent, or cause a default under any
      agreement to which TRMI-H is a party. No consent, approval or filing with
      any Governmental Body is required to authorize the execution and delivery
      of this Agreement by TRMI-H or TRMI-H's performance of the terms of this
      Agreement.

           (e)  Litigation. There is no action, suit, proceeding, claim or
      investigation by any person, entity, administrative agency or Governmental
      Body pending or, to the knowledge of TRMI-H, threatened, against TRMI-H
      that impedes or is likely to impede TRMI-H's ability to consummate the
      transactions contemplated by this Agreement.

           (f)  Title to Shares. TRMI-H is the record owner and sole beneficial
      owner of the Shares. TRMI-H holds the Shares free and clear of any lien,
      pledge, security interest, option, right of first refusal or other adverse
      claim (other than the Option, certain restrictions on transfer and other
      obligations arising under the SPA and restrictions on transfer of the
      Shares arising under the federal and state securities laws).

      10. Adjustment upon Changes in Capitalization, Merger or Recapitalization.
          ---------------------------------------------------------------------

           (a)  In the event of any change in the outstanding shares of Common
      Stock by reason of a stock dividend, stock split, split-up, merger,
      consolidation, recapitalization, combination, conversion, exchange of
      shares, extraordinary or liquidating dividend or


                                       5

<PAGE>

      similar transaction which would have the effect of diluting Optionee's
      rights hereunder, the type and number of shares or securities purchasable
      upon the exercise of the Option and the Exercise Price shall be adjusted
      appropriately, and proper provision will be made in the agreements
      governing such transaction, as shall fully preserve the economic benefits
      provided hereunder to Optionee.

           (b)  Without limiting the foregoing, whenever the number of shares of
      Common Stock purchasable upon exercise of the Option is adjusted as
      provided in this Section 10, the Exercise Price shall be adjusted by
      multiplying the Exercise Price by a fraction, the numerator of which is
      equal to the number of shares of Common Stock purchasable prior to the
      adjustment and the denominator of which is equal to the number of shares
      of Common Stock purchasable after the adjustment.

           (c)  In the event that ECD enters into an agreement (i) to
      consolidate with or merge into any person and ECD will not be the
      continuing or surviving corporation in such consolidation or merger, (ii)
      to permit any person to consolidate with or merge into ECD and ECD will
      not be the continuing or surviving corporation in such consolidation or
      merger, or (iii) to sell or otherwise transfer all or substantially all of
      its assets to any person, then, and in each such case, the agreement
      governing such transaction will make proper provision so that the Option
      will, upon the consummation of such transaction and upon the terms and
      conditions set forth herein, be converted into, or exchanged for, an
      option with identical terms appropriately adjusted to acquire the number
      and class of shares or other securities or property that Optionee would
      have received in respect of the shares of Common Stock subject to the
      Option had the Option been exercised immediately prior to such
      consolidation, merger, sale or transfer or the record date therefor, as
      applicable, and will make any other necessary adjustments. ECD shall take
      such steps in connection with such consolidation, merger, liquidation or
      other such transaction as may be reasonably necessary to assure that the
      provisions hereof shall thereafter apply as nearly as possible to any
      securities or property thereafter deliverable upon exercise of the Option.

      11. Miscellaneous.
          -------------

           (a)  Further Assurances. Each party hereto at the reasonable request
      of the other, shall execute and deliver, or shall cause to be executed and
      delivered from time to time, such further certificates, agreements or
      instruments of conveyance and transfer, assumption, release and
      acquittance and shall take such other action as the other party hereto may
      reasonably request to consummate or implement the transactions
      contemplated by this Agreement. Without limiting the generality of the
      foregoing, if requested by the Optionee in connection with its exercise of
      the Option, TRMI-H shall deliver a certificate to the Optionee, executed
      by a duly authorized officer, confirming that the representations and
      warranties of TRMI-H set forth in Section 9 of this Agreement are true and
      correct on and as of the Closing Date (as such term is defined in the
      Notice of Option Exercise) as though then made. Except as expressly
      provided in the preceding sentence, TRMI-H shall


                                       6

<PAGE>

      not be obligated pursuant to this Agreement to make any additional
      representations or warranties regarding the Shares, the business of ECD
      or any other matter.

           (b)  Notices. Any notice, communication, request, instruction or
      other document required or permitted hereunder shall be given in writing
      and shall be deemed given as follows: (i) by personal delivery when
      delivered personally, (ii) by overnight courier upon written verification
      of receipt, (iii) by telecopy or facsimile transmission when confirmed by
      telecopier or facsimile transmission, or (iv) by certified or registered
      mail, return receipt requested, five (5) days after deposit in the mail.
      All notices shall be delivered to the address of the applicable party as
      set forth below:

                 ECD or OBC:        Energy Conversion Devices Inc.
                                    2956 Waterview Drive
                                    Rochester Hills, Michigan  48309
                                    Attention:  Robert C. Stempel
                                    Tel:  (248) 293-0440
                                    Fax:  (248) 844-1214

                 TRMI-H:            TRMI Holdings Inc.
                                    6001 Bollinger Canyon Road, Building T
                                    San Ramon, California 94583
                                    Attention:  Chief Corporate Counsel
                                    Attention:  Allen H. Uzell
                                    Tel:  (925) 842-1679
                                    Fax:  (925) 842-2056

      Any party may, by written notice so delivered, change its address for
      notice purposes hereunder.

           (c)  Choice of Law. This Agreement shall be construed in accordance
      with, and governed by, the laws of the State of Delaware, without giving
      effect to principles of conflicts of law.

           (d)  Entire Agreement; Amendment. This Agreement, the Master
      Agreement and the other Master Transaction Agreements (as defined in the
      Master Agreement) constitute the entire understanding among the parties
      with respect to the subject matter hereof and thereof, superseding all
      negotiations, prior discussions, representations and prior agreements and
      understandings relating to such subject matter. No amendment of this
      Agreement shall be binding unless agreed to in writing by all parties to
      this Agreement and, in the event the Optionee is not OBC or an affiliate
      of OBC and such amendment would have an adverse effect on the Optionee's
      rights under the Option, Optionee.

           (e)  Successors and Assigns; Assignments; Third Party Beneficiaries.
      This Agreement shall be binding upon and shall inure to the benefit of the
      parties hereto, and,


                                       7

<PAGE>

      except as otherwise prohibited, their respective successors and permitted
      assigns. Neither this Agreement nor any of the rights, interests or
      obligations hereunder may be assigned by any party without the prior
      written consent of the other parties; provided that OBC may transfer its
      rights, interests and obligations as Optionee hereunder (for the
      avoidance of doubt, excluding any other rights, interests and obligations
      of OBC hereunder) without the prior written consent of TRMI-H, subject
      to the restrictions identified in the legend appearing on the first page
      of this Agreement. Nothing in this Agreement shall or is intended to
      confer upon any other person or entity any benefits, rights or remedies.

           (f)  Severability. If any provision herein is contrary to any lawful
      statute, rule, regulation, proclamation or other lawful mandate
      whatsoever, whether or not listed, this Agreement shall be construed as
      modified to the extent necessary to conform with such legal strictures.
      The provisions of this Agreement are severable to the extent the partial
      invalidity of one or more provisions will not affect the validity of the
      Agreement as a whole so long as the economic or legal substance of the
      transactions contemplated hereby is not affected in any materially adverse
      manner as to any party hereto.

           (g)  Waiver. Any party may (i) extend the time for the performance of
      any of the obligations or other acts of any other party hereto or (ii)
      waive compliance with any of the agreements of any other party or with any
      conditions to its own obligations. Any agreement on the part of a party
      hereto to any such extension or waiver shall be valid if set forth in an
      instrument in writing signed on behalf of such party. Except as otherwise
      expressly provided herein, no failure to exercise, delay in exercising, or
      single or partial exercise of any right, power or remedy by any party, and
      no course of dealing between the parties, shall constitute a waiver of any
      such right, power or remedy. No waiver by a party of any default,
      misrepresentation or breach of warranty or covenant hereunder, whether
      intentional or not, shall be deemed to extend to any prior or subsequent
      default, misrepresentation or breach of warranty or covenant hereunder or
      affect in any way any rights arising by virtue of any prior or subsequent
      such occurrence.

           (h)  Expenses. Except as otherwise provided herein, all costs and
      expenses, including without limitation, fees and disbursements of counsel,
      incurred in connection with this Agreement and the transactions
      contemplated hereby shall be paid by the party incurring such costs and
      expenses.

           (i)  Counterparts. This Agreement may be executed in several
      counterparts, and by different parties in separate counterparts, which
      when taken together shall be deemed to constitute one and the same
      instrument.

           (j)  Facsimile Signatures. This Agreement shall become effective upon
      execution and delivery hereof by the parties hereto; delivery of this
      Agreement may be made by facsimile to the parties with original copies
      promptly to follow by overnight courier.


                                       8

<PAGE>

           (k)  Headings. The headings of the Sections, Schedules and Exhibits
      of this Agreement are for guidance and convenience of reference only and
      have no significance in the interpretation of this Agreement or any
      Schedule or Exhibit hereto.

           (l)  Dispute Resolution. Any dispute, controversy or claim relating
      to this Agreement shall be resolved exclusively in accordance with the
      dispute resolution procedures set forth in Section 11(d) of the Master
      Agreement.

           (m)  Status of Stock Purchase Agreement. The parties agree that the
      provisions of the SPA shall continue in full force and effect from and
      after the date of this Agreement; provided that (i) Section 4.3(f) of the
      SPA has been partially waived by ECD as provided in Section 3(c) of this
      Agreement and (ii) Part 4 of the SPA is subject to termination as of the
      Termination Date under the circumstances described in Section 6(c) of this
      Agreement; provided further that, if the Option is exercised in full on
      or before May 31, 2005, TRMI-H agrees that it shall not, without the prior
      invitation of ECD, acquire ECD common stock prior to January 1, 2008.


                            [SIGNATURE PAGE FOllOWS]

                                       9

<PAGE>

            EXECUTED on behalf of ECD, OBC, and TRMI-H as of the date first
above written.

                         ENERGY CONVERSION DEVICES, INC.

                         By: /s/ Robert C. Stempel
                             ---------------------------------------------
                               Robert C. Stempel
                               Chairman and Chief Executive Officer


                         OVONIC BATTERY COMPANY, INC.

                         By: /s/ Robert C. Stempel
                             ---------------------------------------------
                               Robert C. Stempel
                               Chairman


                         TRMI HOLDINGS INC.

                         By: /s/ W.C. Taylor
                             ---------------------------------------------
                               W.C. Taylor
                               Vice President



                          [SIGNATURE PAGE TO OPTION AGREEMENT]


<PAGE>

                                    EXHIBIT A

        FORM OF NOTICE OF OPTION EXERCISE AND STOCK PURCHASE AGREEMENT

                            [LETTERHEAD OF OPTIONEE]

[Date]

TRMI Holdings Inc.
6001 Bollinger Canyon Road, Building T
San Ramon, California 94583
Attention:  Chief Corporate Counsel
Attention:  Allen H. Uzell
Tel:  (925) 842-1679
Fax:  (925) 842-2056

      Re:  Notice of Option Exercise and Stock Purchase Agreement

This Notice of Option Exercise and Stock Purchase Agreement (this "Purchase
Agreement") is delivered pursuant to Section 3 of that certain Option Agreement
(the "Option Agreement") dated as of November __, 2004 among Ovonic Battery
Company, Inc. ("OBC"), Energy Conversion Devices, Inc. ("ECD") and TRMI Holdings
Inc. ("TRMI-H"). Capitalized terms used but not defined herein shall have the
respective meanings given them in the Option Agreement.

The undersigned Optionee hereby gives notice to TRMI-H that it elects to
exercise the Option and shall purchase [INSERT NUMBER OF SHARES] shares of
Common Stock subject to the Option (the "Securities") on [INSERT CLOSING DATE]
(the "Closing Date") on the terms and subject to the conditions set forth in the
Option Agreement and this Purchase Agreement.

The closing of the purchase and sale of the Securities (the "Closing") shall
take place at the offices of TRMI-H located at ____________________________ at
9:00 a.m. on the Closing Date.

In addition to any other deliveries required under the Option Agreement, at the
Closing, (a) Optionee shall deliver to TRMI-H the Exercise Price by wire
transfer of immediately available funds to TRMI-H's account number [number] at
[bank] (or such other account or accounts as TRMI-H shall have notified Optionee
in writing) and (b) TRMI-H shall deliver to Optionee the certificate or
certificates representing the Securities; provided that in the event Optionee is
not OBC or an affiliate of OBC, TRMI-H shall deliver such certificate or
certificates to ECD and ECD shall issue and deliver to Optionee a new stock
certificate in accordance with Section 3 of the Option Agreement.

Optionee acknowledges and agrees that the purchase and sale of the Securities
pursuant to the Option Agreement and this Purchase Agreement have not been and
will not be registered under the Securities Act of 1933, as amended (the
"Securities Act") and that the Securities may not be sold,


<PAGE>


transferred, or otherwise disposed of without registration under the
Securities Act or an exemption from registration thereunder, and that in the
absence of an effective registration statement covering the Securities, or an
available exemption from registration under the Securities Act, the Securities
must be held indefinitely. Optionee further acknowledges that each certificate
representing the Securities shall be endorsed with a legend substantially in the
form identified in Section 3 of the Option Agreement and agrees that it will
comply with the transfer restrictions set forth in such legend.(1)

IN WITNESS WHEREOF, OPTIONEE has executed this Notice of Option Exercise and
Stock Purchase Agreement as of the date first set forth above.


                                    [NAME OF OPTIONEE]


                                    By:
                                        --------------------------------------






------------------------------
(1)   Paragraph to be included if the offer and sale of the Shares are not
covered by a registration statement that has been declared effective by the
Commission.


<PAGE>

                                    EXHIBIT B

                     FORM OF OPINION OF COUNSEL TO OPTIONEE

                        [Baker & McKenzie LLP Letterhead]


                              _______________, 200_



Board of Directors
Energy Conversion Devices, Inc.
2956 Waterview Drive
Rochester Hills, Michigan 48309

      Re:   Exercise of Option Granted by TRMI Holdings Inc.
            -----------------------------------------------

Ladies and Gentlemen:

      Energy  Conversion  Devices,   Inc.  (the  "Company"),   Ovonic  Battery
Company,  Inc., a subsidiary  of the Company  ("OBC"),  and TRMI Holdings Inc.
("TRMI-H")  are  parties to an Option  Agreement  dated as of December 2, 2004
(the  "Option  Agreement")  pursuant to which TRMI-H has granted OBC an option
(the  "Option") to purchase  4,376,633  shares of the Company's  Common Stock,
par value $.01 per share ("Common Stock").

      We understand  that OBC intends to exercise the Option as of the date of
this letter with  respect to  __________  shares of Common  Stock.  We further
understand that the aggregate  exercise price payable in connection with OBC's
exercise of the Option is $_____________ in cash (the "Exercise Price").

      In connection with the foregoing exercise of the Option, you have
requested our opinion that the payment of the Exercise Price upon the exercise
of the Option by OBC, if viewed as a stock purchase or redemption of Common
Stock by the Company, would not constitute an unlawful stock purchase or
redemption for which the directors of the Company would have personal liability
under the Delaware General Corporation Law (the "DGCL").


<PAGE>


Summary of Applicable Provisions of the DGCL

      Under Section 170 of the DGCL, the directors of a Delaware corporation are
permitted to declare and pay dividends only out of the corporation's "surplus"
or, if there is no surplus, then out of the net profits of the corporation for
the current and preceding fiscal year. Section 154 of the DGCL defines "surplus"
to mean the excess of the "net assets" of a corporation over its "capital." "Net
assets" is defined for this purpose to mean the amount by which a corporation's
total assets exceed its total liabilities. Capital and surplus are disregarded
in the calculation of net assets. For a corporation that has authorized shares
with a stated par value, the "capital" of the corporation is in most cases equal
to the aggregate par value of the corporation's issued and outstanding shares.

      The DGCL permits a corporation to purchase or redeem its own shares as
long as the purchase or redemption does not occur when the corporation's capital
is impaired and the transaction would not result in any impairment of capital. A
purchase or redemption is deemed to impair a corporation's capital if the value
of the consideration paid in the transaction exceeds the amount of the
corporation's surplus.

      Under Section 174 of the DGCL, the directors of a Delaware corporation may
in certain cases incur personal liability with respect to violation of the
provisions of the DGCL prohibiting unlawful dividends, stock purchases and
redemptions.

      Option Exercise Transaction

      Although the Option is exercisable for shares of the Company's Common
Stock, the Option was granted to and is being exercised by OBC. Accordingly, it
may be argued that the provisions of the DGCL relating to stock purchases and
redemptions are not applicable to the exercise of the Option. Because OBC is a
91.7 percent-owned subsidiary of the Company, however, you have requested that
our opinion that the transaction, if viewed as a purchase or redemption of
Common Stock by the Company, would be lawful under the provisions of the DGCL
discussed above.

      Assumptions

      We have been provided with a schedule prepared by Grant Thornton LLP, the
Company's independent auditors, indicating that the Company's surplus as of [end
of preceding fiscal quarter] was $_____ million, calculated in accordance with
the DGCL based on the Company's [un]audited consolidated financial statements as
of that date prepared in accordance with generally accepted accounting
principles. A copy of the schedule is attached to this letter. We have assumed
that the information set forth in the attached schedule is accurate and complete
in all respects.

      We have also received a certificate, executed on behalf the Company by its
Chief Financial Officer, stating, among other matters, that based on the amount
of the Company's current total assets and total liabilities and the number of
shares of the Company's Common


<PAGE>


Stock currently outstanding, the Company's surplus on the date of this letter
is not less than $___________. A copy of the certificate is attached to this
letter. We have assumed that the information set forth in the attached
certificate is accurate and complete in all respects.

      Opinion

      Based on the foregoing, we are of the opinion that the exercise of the
Option and payment of the Exercise Price, if viewed as a purchase or redemption
of Common Stock by the Company, would not constitute an unlawful stock purchase
or redemption for which the directors of the Company would have personal
liability pursuant to the DGCL.

      Qualifications and Limitations

      In reaching our opinion set forth in this letter, we have relied only upon
our examination of the foregoing schedules and certificates and we have made no
independent verification of the financial calculations, valuations or other
factual matters set forth in such documents.

      Our opinion set forth in this letter is limited to the DGCL referred to in
this letter and we express no opinion with respect to the effect or application
of any other laws, including the possible effect or application of laws relating
to bankruptcy, insolvency, fraudulent conveyance, fraudulent transfer or other
similar laws or judicial doctrines.

      Our opinion set forth in this letter is limited to the application of the
specific provisions of the DGCL referred to in this letter to the Company and we
have not been requested to, and do not, express any opinion with respect to any
matters relating to OBC or with respect to the compliance by the Company's
directors with their fiduciary duties in connection with the authorization of
the Option Agreement, any related agreement or any of the transactions
contemplated thereby. Further, we have not been requested to, and do not,
express any opinion with respect to any agreement or transaction between the
Company, ChevronTexaco Corporation and their respective affiliates other than
our opinion with respect to the Option Agreement as set forth in this letter.


<PAGE>


      This letter is limited to the matters stated herein, and no opinion is
implied or may be inferred beyond the matters expressly stated. The Company is
authorized to provide a copy of this letter to TRMI-H in connection with the
exercise of the Option, but TRMI-H and its affiliates are not authorized to rely
on this letter for any purpose. Without our prior written approval, this letter
may not be relied upon by any person or entity other than you, quoted in whole
or in part or otherwise referred to in any report or document, furnished to any
other person or entity (other than as expressly permitted pursuant to the
preceding sentence) or relied upon for any purpose other than in connection with
consummating the transactions described herein.


                                    Very truly yours,


                                    BAKER & McKENZIE LLP





<PAGE>


                                    EXHIBIT C

                       FORM OF REPRESENTATION CERTIFICATE

                           REPRESENTATION CERTIFICATE

      This Representation Certificate is delivered in connection with the
exercise of the Option pursuant to that certain Option Agreement among Ovonic
Battery Company, Inc. ("OBC"), Energy Conversion Devices, Inc., a Delaware
corporation ("ECD"), and TRMI Holdings Inc., a Delaware corporation ("TRMI-H"),
dated as of November __, 2004 (the "Option Agreement") and that certain Notice
of Option Exercise and Stock Purchase Agreement dated as of ____________
delivered to TRMI-H by Optionee (the "Purchase Agreement"). Capitalized terms
used but not defined in this Representation Certificate shall have the
respective meanings given them in the Option Agreement.

      The undersigned hereby represents and warrants to TRMI-H as follows:

      1. Authorization; Binding Obligation. Optionee has full power and
         ---------------------------------
authority to exercise the Option and to enter into the Purchase Agreement and
the Purchase Agreement when executed and delivered, will constitute a valid and
legally binding obligation of Optionee.

      2. Purchase Entirely for Own Account. The Common Stock to be received by
         ---------------------------------
Optionee upon exercise of the Option (the "Securities") will be acquired for
investment for Optionee's own account, not as a nominee or agent, and not with a
view to the resale or distribution of any part thereof in violation of the
registration requirements of the Securities Act of 1933, as amended (the
"Securities Act"), and Optionee has no present intention of selling, granting
any participation in, or otherwise distributing the same in violation of the
Securities Act. By executing this Representation Certificate, Optionee further
represents that it does not have any contract, undertaking, agreement or
arrangement with any person to sell, transfer or grant participations to such
person or to any third person, with respect to any of the Securities to the
extent the same would violate the Securities Act.(2)

      3. Receipt of Information. Optionee believes it has received all the
         ----------------------
information it considers necessary or appropriate for deciding whether to
purchase the Securities. Optionee further represents that it has had an
opportunity to ask questions and receive answers from ECD regarding the
business, properties, prospects and financial condition of ECD.

      4. Investment Experience. Optionee acknowledges that it is able to fend
         ---------------------
for itself, can bear the economic risk of its investment in the Securities, and
has such knowledge and experience





-------------------------
(2)   To be included if the sale of the Shares has not been registered under
the Securities Act.


<PAGE>

in financial or business matters that it is capable of evaluating the merits
and risks of the investment in the Securities.  If other than an individual,
Optionee also represents it has not been organized for the purpose of acquiring
the Securities.

      5. Accredited Investor. Optionee is an "accredited investor" within the
         -------------------
meaning of Rule 501 of Regulation D under the Securities Act, as presently in
effect.

      6. Restricted Securities. Optionee understands that the Securities it is
         ---------------------
purchasing are characterized as "restricted securities" under the federal
securities laws inasmuch as they are being acquired from TRMI-H in a transaction
not involving a public offering and that under such laws and applicable
regulations such securities may be resold only in certain limited circumstances
without registration under the Securities Act. Optionee represents that it is
familiar with Rule 144 under the Securities Act, as presently in effect, and
understands the resale limitations imposed thereby and by the Securities Act.(3)

      7. Non-U.S. Optionees. If Optionee is not a United States person, Optionee
         ------------------
hereby represents that he or she has satisfied himself or herself as to the full
observance of the laws of his or her jurisdiction in connection with any
invitation to purchase the Option or the Securities or any use of the Option
Agreement, including (i) the legal requirements within his or her jurisdiction
for the purchase of the Securities, (ii) any foreign exchange restrictions
applicable to such purchase, (iii) any governmental or other consents that may
need to be obtained, and (iv) the income tax and other tax consequences, if any,
that may be relevant to the purchase, holding, sale, or transfer of the
Securities and further represents that Optionee's subscription and payment for,
and his or her continued beneficial ownership of the Securities, will not
violate any applicable securities or other laws of his or her jurisdiction.

                                    [NAME OF OPTIONEE]


                                    By:
                                      --------------------------------------
                                      Name:
                                      Title:





---------------------
(3)   To be included if the sale of the Shares has not been registered under the
Securities Act.

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