Re: ThinkJet batteries from Ebay Message #7 Posted by glynn on 3 May 2003, 7:38 p.m., in response to message #6 by Ellis Easley
Except where moisture/humidity or temp extremes are involved. Once the battery gets furry on top, don't trust it.
ALSO: packs are subject to things that individual cells aren't. There is such a thing as "cell reversal", which comes about because cells can't be made all perfect and with exactly the same capacity.
If you string three cells, say, in series, and the actual capacity of each is, say, 502mA, 499mA, 501mA-- as the cell self-discharges, the middle one empties first. Then cell one and cell three have a differential to equalize between them. In practice, the tolerances on cell capacities vary much more than my little example, and sometimes the differential between cells is enough to cause a backwards flow through the middle cell, killing it with a "short". Then once you've lost a cell, charging the pack as a 3.6v unit is wrong, because now it is a 2.4v pack.
For reasons above, pack manufacturers usually ship the packs "unformed", meaning they don't charge the whole to its fullest extent. This reduces reversal problems on the shelf. 1-3 charge cycles "form" the pack to its fullest capacity.
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