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Archive for September 13th, 2009

NiMH Cells: Finding the Weak Link

I recently bought two dozen Tenergy Ready-to-Use NiMH cells, rated at 2.3 Ah, with the intent of making up three 8-cell packs (identified as A, B, and C, for lack of anything smarter) for the amateur radio HTs we use on our bikes. However, one of the packs measured a consistently short runtime and I suspected one weak cell.

So I ran pairs of cells from the weak pack and found these results:

DSC-H5 Battery - Tenergy RTU NiMH AA Cells

DSC-H5 Battery - Tenergy RTU NiMH AA Cells

Observations…

These are all measured just after charging, so they’re all the best you can expect from the cells. I haven’t done any self-discharge tests yet.

The overall capacity at 1 A load is roughly 65% of the 2.3 Ah rating.

The red trace falls far short of the others, so that’s the pair with the weak cell. I charged & tested those two cells individually, which are the lower two traces: cell A4 has 58% of nominal capacity. Admittedly, that’s 90% of the capacity of the rest, but, still …

I’ll use the other three pairs of cells through the Sony DSC-H5 camera, for reasons described there. Cell A4 is destined for the shelf…

Now, the question becomes: who should I buy the next batch of cells from?

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