From: Henry Spencer <firstname.lastname@example.org>
Subject: Re: NiCd Memory
Date: Fri, 10 Oct 1997 12:53:09 GMT
In article <email@example.com>,
> I've heard aboout two different sorts of memory in a NiCd battery.
>One is by cycling WITHOUT overcharging and only occurs after many hundred
>cycles, and can be wiped out simply by discharging to 1V per cell or
Basically correct -- although as far as I know, a discharge is the only
way to get rid of it -- but this effect, the true memory effect, occurs
*only* when the battery is repeatedly discharged to *exactly* the same
point. Satellite batteries are about the only real batteries whose
charge/discharge cycle is controlled precisely enough to exhibit genuine
> The other memory I have heard of is caused by cumulative overcharge
>and is called voltage depression and can occur in only about 50 cycles.
This is not memory effect at all. The battery still retains essentially
all of its capacity; it merely delivers it at a slightly lower voltage.
It's often mistaken for memory effect because a lot of stupid circuits try
to sense the charge state of NiCds by measuring their voltage -- a poor
method at best, since NiCd voltage curves are pretty flat. Much of the
folklore about NiCd memory comes from stupid circuits incorrectly deciding
that a battery is empty when in fact it's nearly full but suffering from
>...It too can be wiped out by cycling to 1V per cell.
Note: NiCd discharging should be done on the individual cells, not on the
battery as a whole. If you try to discharge the battery as a whole, it's
quite likely that some cells will hit full discharge a bit early, and the
remaining ones will then reverse-charge them... which kills NiCd cells
If NT is the answer, you didn't | Henry Spencer
understand the question. -- Peter Blake | firstname.lastname@example.org