User rebuilt battery

Jan 06, 2008 2 Replies
B

Hi folks,



As a refreshing change of pace, there are two known examples of NHW11,



2001-03, battery packs being rebuilt. The first is in Europe by Florian Steiper in Germany and a collaborative effort between Eric and myself:

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The photo is my battery assembly reconditioning unit using an MRC 989 and two custom built end plates. When an NiMH battery charges, it can generate gas if over charged. One of my end-plates has a capacitance load cell that at 13.3 nF is only under clamp pressure, not gas pressure.



I have three spare cells and will pickup an additional 36 cells for refurbishment the end of this month. At $30-40 each, this means a failed battery pack can have just the failed cells replaced and get back on the road again.



Both battery repairs occurred in Nov-Dec so it is too soon to know how long they will last. But for now, two NHW11 Prius have been returned to service for a lot less than a complete battery pack replacement.



Comments? Questions? Concerns?



Bob Wilson


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N

I'm impressed. A few times in my distant past it became necessary to identify and replace a bad cell in a high-voltage series set, and it rarely worked as well as the original. That was probably due to careful matching.

It will be great if you provide more information as time goes on...

Nice!

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B

Thanks!

What I did was ship the battery fully charged, this means above the standard 80% limit. The instruction to the user was to discharge the cell assembly until the no-load voltage matched that the of the adjact cells.

Normally, our Prius battery packs wander between 40-80% but sit mostly at about 60%. This means there is 'head room' so imperfections between the cell assemblies seldom leads to over/under charge conditions.

But battery assemblies that run closer to 100% down to 0% are especially sensitive to balanced cells. In fact, it would be nearly impossible to achieve long battery life if all of the cells has to match at these extreme charge ranges.

Bob Wilson

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