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One of the most common causes of premature failure in rechargeable batteries is backdriving; if a somewhat weak cell is put in a series with a stronger one, the stronger one may push current through the weaker one, damaging it severely.
It is therefore imperative that in any application in which
cells will be close to totally discharged, rechargeable batteries always be used in reasonably well-matched sets. Otherwise, whichever cell happens to be weakest will be damaged if it is drained before the others; this cell will then be harmed even more the next time it is used, etc.
Unfortunately, assembling matched cells isn't always as easy as one might like. If a device requires six cells and they come in two-packs, there's no way of knowing for sure that all six cells match. Likewise if one stops using one product that uses rechargeable batteries and wants to use them in a product which requires a different number, there's no good way of getting a matched set aside from buying all new batteries.
I would propose that a rechargeable battery charging unit that includes a function to cycle batteries and measure their performance on the charge/discharge cycles. This would allow someone who uses rechargeable batteries in several devices to rotate the batteries so as to ensure continuing optimal balance.
Why Batteries Haven't Kept Up
http://slashdot.org...id=02/03/04/1153237
Batteries have grown at standard normal industrial rates - which are much slower then Moore's Law, and hence, the source of our problem. [LoriZ]
Battery discharger / Capacity meter
http://www.elektor-.../details/e1101u.htm
First part of two-part article, on Elektor Electronics U K Magazine - Issues Nov & Dec 2001 [LoriZ, Mar 05 2002, last modified Oct 21 2004]
Battery discharger / Capacity meter
http://www.elektor-.../details/e1101u.htm
First part of two-part article, on Elektor Electronics U K Magazine - Issues Nov & Dec 2001 [neelandan, Apr 04 2002, last modified Oct 04 2004]
[link]
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I have seen a series of articles in an electronics magazine (Elektor) addressing this very problem. Fully charged cells are discharged and their discharge curves plotted by a microcontroller and sent to a PC for display. |
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The Elektor link gives plans to build a battery discharge measuring device; certainly such devices, as 'lab equipment', have been around for decades (if nothing else, just use a battery, resistor, and strip-chart recorder). |
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There's a bit of a difference, though, between that and a device which can take a set of four batteries and simultaneously charge and measure them and provide a couple of 'summary figures' describing their state. |
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To put it another way, the concept of measuring battery performance is hardly new, but I'm unaware of any efforts to use such data for 'grouping' similarly-performing batteries, nor of any devices optimized toward that goal. |
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