Alt-BEAM Archive
Message #01690
To: beam@corp.sgi.com
From: Wouter Brok w.j.m.brok@stud.tue.nl
Date: Tue, 23 Mar 1999 08:56:36 +0100
Subject: [alt-beam] Re: Solar charger for NI-CAD walker...
Hello,
Just wanted to tell that at present I'm building a two-motor walker with a
NiCd-battery, charged by solarcells.
I use three 24x33 (is this a standard size, I'm not sure) sunceram cell (in
series), in series with a 1N5817 diode. This is connected to the poles of a
3.6V, 60mAh NiCd battery (the one the use as a BIOS-backup-battery) and to
the circuitry as well.
In spring-sun I measured a charge-current of 14.6 mA and in my room it
varried from 1 mA to something like 8 mA near the window. Leakage-current
is the dark is about 700 nA.
The diode-idea I got from somebody (sorry, I forgot who), after I posted a
question on the list. Later I disassembled a commercial
solar-battery-charger and I found the 1N5817 in it, which I think has a low
threshold-voltage (about 2.0 V) if I measured it correctly.
My idea about the memory-effect of the NiCd's was that I should charge and
discharge the battery in 'the proper way' once in a while, like Steven
mentioned already.
Wouter Brok
> I was going through my 1000 Circuits book from none other than Forrest
>Mims and found a circuit for a solar charger. I was thinking that I could
>implement a solarize my walker by trickle charging a NICAD with a solar
>cell. My question is this - can you be charging a nicad and drawing from it
>at the same time - I think that NICADS have memory, so would this damage the
>battery's ability to store its maximum power level? Also, the circuit I
>have doesn't seem to have any protection against overcharging - anyone know
>how to implement this?
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