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Path: utzoo!watmath!watcgl!dmmartindale
From: dmmartindale@watcgl.UUCP (Dave Martindale)
Newsgroups: net.consumers,net.physics
Subject: Re: lifetime of rechargeable batteries
Message-ID: <340@watcgl.UUCP>
Date: Tue, 6-Nov-84 12:09:18 EST
Article-I.D.: watcgl.340
Posted: Tue Nov  6 12:09:18 1984
Date-Received: Wed, 7-Nov-84 07:17:32 EST
References: <1789@garfield.UUCP> <488@aluxe.UUCP>
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Organization: U of Waterloo, Ontario
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More info on nicads:
Real "D" cell nicads are made, and can be found at large electronic
distributors.  They cost a lot though, and require a different charger,
since a charger that puts out an appropriate charge rate for C cells
will not fully charge a real D cell.

Nicad batteries are used in some business jets as the main battery.
They put out more current than a lead-acid battery, which translates
into a faster rate of acceleration of the turbine when starting a
jet engine, which results in less wear to the engine.  In this
use, the "memory" effect is well known, and after the battery has been
used for a certain number of engine starts it is serviced.  It is
fully discharged to see how much power it can still deliver; if that
is less than some high percentage of the original output, it is
recharged and discharged again to see if its capacity has improved.
When it can't be rejuvenated, it will be replaced.

One potential problem with discharging by leaving a battery-powered
appliance on for a long time:  If some cells hold a bit more charge
than others (due to production non-uniformities or age) then when
you do this, one cell will reach zero output first, and then start
reverse-charging as the other cells continue forcing current
through it.  This is a good way of developing a short in the cell.
You probably want to discharge the cells to the point where output
drops drastically - the cells are almost discharged at that point.