Exhibit 99.4

Certification Pursuant to Section 302  of the Sarbanes-Oxley Act of 2002

I, John Sheridan, certify that:

|1. | I have reviewed this annual report on Form 40-F of   Ballard Power Systems Inc.;                                                                                                                                                                                                                                                    
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|2. | Based on my knowledge, this report does not contain   any untrue statement of a material fact or omit to state a material fact   necessary to make the statements made, in light of the circumstances under   which such statements were made, not misleading with respect to the period   covered by this annual report;           
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|3. | Based on my knowledge, the financial statements, and   other financial information included in this report, fairly present in all   material respects the financial condition, results of operations and cash   flows of the issuer as of, and for, the periods presented in this report;                                           
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|4. | The issuers other certifying officer and I are   responsible for establishing and maintaining disclosure controls and   procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and   internal control over financial reporting (as defined in Exchange Act Rules   13a-15(f) and 15d-15(f)) for the issuer and have:
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|5. | The issuers other certifying officer and I have   disclosed, based on our most recent evaluation of internal control over   financial reporting, to the issuers auditors and the audit committee of the   issuers board of directors (or persons performing the equivalent functions):                                           
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|   | b)                                                                                                                                                                                                                                                                                                                                  

|Date: March 26, 2007                  | 
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|/s/ John Sheridan                     | 
|                                      | 
|President and Chief Executive Officer | 

A signed original of this written statement required by Section 302 has been provided to Ballard Power Systems Inc. and will be retained by Ballard Power Systems Inc. and furnished to the Securities and Exchange Commission or its staff upon request.



Certification Pursuant to Section 302  of the Sarbanes-Oxley Act of 2002

I, Dave Smith, certify that:

|1. | I have reviewed this annual report on Form 40-F of   Ballard Power Systems Inc.;                                                                                                                                                                                                                                                    
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|   |                                                                                                                                                                                                                                                                                                                                     
|2. | Based on my knowledge, this report does not contain   any untrue statement of a material fact or omit to state a material fact   necessary to make the statements made, in light of the circumstances under   which such statements were made, not misleading with respect to the period   covered by this annual report;           
|   |                                                                                                                                                                                                                                                                                                                                     
|3. | Based on my knowledge, the financial statements, and   other financial information included in this report, fairly present in all   material respects the financial condition, results of operations and cash   flows of the issuer as of, and for, the periods presented in this report;                                           
|   |                                                                                                                                                                                                                                                                                                                                     
|4. | The issuers other certifying officer and I are   responsible for establishing and maintaining disclosure controls and   procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and   internal control over financial reporting (as defined in Exchange Act Rules   13a-15(f) and 15d-15(f)) for the issuer and have:
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|   | a.                                                                                                                                                                                                                                                                                                                                  
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|   | b.                                                                                                                                                                                                                                                                                                                                  
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|   | d.                                                                                                                                                                                                                                                                                                                                  
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|5. | The issuers other certifying officer and I have   disclosed, based on our most recent evaluation of internal control over   financial reporting, to the issuers auditors and the audit committee of the   issuers board of directors (or persons performing the equivalent functions):                                           
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|   | a.                                                                                                                                                                                                                                                                                                                                  
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|   | b.                                                                                                                                                                                                                                                                                                                                  

|Date: March 26, 2007    | 
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|                        | 
|                        | 
|/s/ Dave Smith          | 
|                        | 
|Chief Financial Officer | 

A signed original of this written statement required by Section 302 has been provided to Ballard Power Systems Inc. and will be retained by Ballard Power Systems Inc. and furnished to the Securities and Exchange Commission or its staff upon request.