Repair FEW/MMH Battery - GreenHybrid - Hybrid Cars

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Old 04-11-2017, 07:46 AM
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Default Repair FEW/MMH Battery


I'm researching hybrid SUVs and the FEH/MMH seems to offer a good combo. I'm a DIYer and was hoping that some folks could tell me if the battery in these cars would be reparable via cells purchased individually and replaced. The Dorman replacement is about 3k, unfortunately.

From what I can tell, the pack itself seems to be easily accessible and the cells seem to be accessible as well. Is this something that someone else has done? Would it even require removing the pack from the car to remove and diagnose the sanyo cells? any guidance would be appreciated. Thanks.
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Old 04-11-2017, 01:01 PM
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Default Re: Repair FEW/MMH Battery

The cells are welded in series forming 5 cell "sticks". Individual cell replacement would be VERY impractical; however, replacement of 5 cell sticks is relatively straightforward.

Doing it in the car, while possible, would be vastly more difficult than outside the car on a suitable table or other work space.

The battery is not made with DIY disassembly in mind. I've disassembled most types of Toyota packs, and the FEH pack is significantly more cumbersome and complex than the worst Toyota pack.

1) Identifying which of the 250 cells are bad.
2) Obtaining a reliable replacement.
3) Disassembly/replacement/reassembly without breaking something.

You would likely benefit more by obtaining a complete pack from a salvage yard and replacing the whole thing.

Lastly, the FEH battery has been extremely reliable. The cooling system is pretty much the best of all the NiMH hybrids out there. I didn't believe it at first, but all my subsequent research and experience suggests it's true. The biggest "failure" is those that sit for extended periods and discharge the hybrid battery to the point that it can't start the ICE. For 2007 and earlier, this is a non-issue due to the build-in hybrid battery jump starter that uses the 12V to charge the HV battery. This was removed sometime after 2007 with the claim that it was never needed - I am aware of at least four examples where it was needed - one where I manually charged a MMH battery sitting at 250V, a youtube video demonstrating its use in an inop FEH and at least two posts on this forum claiming issue on later years where the jump start system was removed.
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Old 04-11-2017, 01:17 PM
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Default Re: Repair FEW/MMH Battery

Thanks a lot for the input.

I've called a few repair shops, and all seem to indicate that they're not familiar with replacing the packs, so it does indicate that they endure well.
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Old 04-11-2017, 08:42 PM
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Default Re: Repair FEW/MMH Battery

Yeah, it's usually best to replace the whole pack. I have an entire pack I'm selling for 400 if Wisconsin is close to you at all.
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Old 04-13-2017, 01:49 AM
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Default Re: Repair FEW/MMH Battery

Ebay always has used FEH batteries. Prices vary a lot, but start around $500. Those are asking prices, not selling prices.
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Old 04-20-2017, 08:01 PM
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Default Re: Repair FEW/MMH Battery

Originally Posted by xspirit View Post
Ebay always has used FEH batteries. Prices vary a lot, but start around $500. Those are asking prices, not selling prices.
Yeah and looking at how few actually sell is more proof on the reliability of them.
If they were problematic with the vast number of them on the road someone would probably be making new replacement 5 cell sticks. I hope someone someday will manufacture quality replacements. I plan to be driving my MMH for 50 years
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