2001-03 battery experiment

Hi

With insights from the "Prius_Technical_Group" group, I'm working on reconditioning individual cell assemblies for NHW11 batteries. For example, the cell assembly in the photo has an ending capacity of 3.2 Ahr, enough to match the cells in a used pack that has suffered one or more failed cell assemblies:

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The automated battery conditioner first discharges the cell assembly to 1 VDC. It then charges it up and records the capacity. Three full cycles appear to give consistent results. NiMH charging generates gas so the battery must be clamped to prevent the sides from bowing out and destroying the cell.

The batteries have interlocking 'cups' and 'dimples' and using just a flat board would lead to local, mechanical stress on the sides. So a pair of plastic shims cover each side providing strain relief for these raised surfaces. One board has a capacitive, load sensor to detect excessive gas pressure:

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This approach takes usable cell assemblies from a salvage battery or one with bad modules (preferred) and reconditions the working cells. Someone with a failed battery pack can get replacement cell assemblies, ~$30-40 each, and replace just failed cell units. This won't be a 'new' battery pack but a reworked pack, good enough to keep the Prius rolling for a lot less than the $2,300+ of a whole battery pack.

Questions? Comments? Concerns?

Bob Wilson