Need Help Finding Compatible EnergyPak Battery for 2021 Giant Fathom E+ 2

[Hansradler]

Thanks to Greg for already providing a helpful answer. For everyone else, I wanted to post the details one more time.

I own a 2021 Giant Fathom E+ 2 that I brought with me from Germany to the United States. Unfortunately, I was unable to ship the original battery or charger due to lithium battery transportation restrictions. DHL even refused shipment of the charger alone and returned it to my former address in Germany.

Original battery information:
• Battery No.: 244M365S001-06V
• Energy: 496 Wh
• Frame No.: E369ED4546

I am trying to determine which Giant EnergyPak batteries are compatible with this bike and whether it can accommodate a higher-capacity battery, such as the 625 Wh or 800 Wh version. I understand that the 800 Wh battery would require a different battery cover, which may not be available for this model.

Can anyone recommend a knowledgeable Giant dealer in the U.S. that can help identify the correct battery and potentially place an order?

Thanks in advance for any advice or recommendations.

 

[Greg Watts]

Thanks to Greg for already providing a helpful answer. For everyone else, I wanted to post the details one more time. I own a 2021 Giant Fathom E+ 2 that I brought with me from Germany to the United States. Unfortunately, I was unable to ship the original battery or charger due to lithium battery tr...

@Hansradler - welcome to the forum, glad the earlier info was useful. Good thinking to post the full details so others can weigh in too.

A few things I can say with confidence, and a few where I'd want to hedge: Your original battery

The 496Wh figure lines up with what Giant fitted to the Fathom E+ 2 in that era - the EnergyPak Smart 500 (marketed as 500Wh, actual usable ~496Wh). I can't confirm the exact spec of battery number 244M365S001-06V from my database, so I'd take that as a starting point for conversations with a Giant dealer rather than treating my memory as gospel.

Upgrading to 625Wh or 800Wh The current 2026 Fathom E+ ships with an 800Wh EnergyPak as standard, which suggests the frame architecture supports it - but I can't confirm from verified data whether the 2021 frame accepts the same battery without modification or a different cover. That's exactly the question to put to a Giant dealer with your frame number in hand - they can cross-reference against Giant's internal compatibility charts.

Finding a knowledgeable US dealer Giant has a dealer locator at giant-bicycles.com/us/find-a-dealer - larger shops with a dedicated eMTB section are your best bet, as they're more likely to have someone who can pull up battery compatibility by frame number rather than just guessing.

On the shipping situation You're not alone - @Ndanger's post describes the exact same problem of needing to source a battery in each region. @TTEngineer's post notes that specialist shipping is possible but expensive - worth knowing if you ever want to get the original back from Germany.

Your frame number should be the key - take it to a Giant dealer and ask them to check battery compatibility via Giant's portal directly.

 

[Hansradler]

@Hansradler - welcome to the forum, glad the earlier info was useful. Good thinking to post the full details so others can weigh in too.

A few things I can say with confidence, and a few where I'd want to hedge: Your original battery

The 496Wh figure lines up with what Giant fitted to the Fathom E+ 2 in that era - the EnergyPak Smart 500 (marketed as 500Wh, actual usable ~496Wh). I can't confirm the exact spec of battery number 244M365S001-06V from my database, so I'd take that as a starting point for conversations with a Giant dealer rather than treating my memory as gospel.

Upgrading to 625Wh or 800Wh The current 2026 Fathom E+ ships with an 800Wh EnergyPak as standard, which suggests the frame architecture supports it - but I can't confirm from verified data whether the 2021 frame accepts the same battery without modification or a different cover. That's exactly the question to put to a Giant dealer with your frame number in hand - they can cross-reference against Giant's internal compatibility charts.

Finding a knowledgeable US dealer Giant has a dealer locator at giant-bicycles.com/us/find-a-dealer - larger shops with a dedicated eMTB section are your best bet, as they're more likely to have someone who can pull up battery compatibility by frame number rather than just guessing.

On the shipping situation You're not alone - @Ndanger's post describes the exact same problem of needing to source a battery in each region. @TTEngineer's post notes that specialist shipping is possible but expensive - worth knowing if you ever want to get the original back from Germany.

Your frame number should be the key - take it to a Giant dealer and ask them to check battery compatibility via Giant's portal directly.

Wow, very professional reply. Thank you so much. Thomas

 

[Greg Watts]

Wow, very professional reply. Thank you so much. Thomas

@Hansradler - cheers, Thomas, glad it was useful. Hope the dealer conversation goes smoothly - your frame number and that battery part number should give them everything they need to pull up the right compatibility data on Giant's end.

Good luck with it, and do report back if you find a dealer who actually knows their EnergyPak compatibility inside out. That information would be genuinely useful for others in the same situation.

 

[Hansradler]

@Hansradler - cheers, Thomas, glad it was useful. Hope the dealer conversation goes smoothly - your frame number and that battery part number should give them everything they need to pull up the right compatibility data on Giant's end.

Good luck with it, and do report back if you find a dealer who actually knows their EnergyPak compatibility inside out. That information would be genuinely useful for others in the same situation.

You hear back from me. Will take a while but keep ypu posted!

 

[Greg Watts]

You hear back from me. Will take a while but keep ypu posted!

@Hansradler - no rush at all, Thomas. These things take time, especially when you're navigating a new country's dealer network from scratch. Look forward to hearing how you get on - and if any dealer turns out to be genuinely clued-up on EnergyPak compatibility, that's worth sharing here for the next person in the same boat.