RE: NiCd Battery Storage

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jeff W. Parisse by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jparisse-at-teslacoil-dot-com>

Gary,

Modern NiCad's pack quite a punch!

I fly large NiCad packs in model airplanes (16 1700mAh cells at 40A peak
for 5 minutes) and the jury is out on storage but many, including
myself, store them discharged (used multiple times or not) for safety
sake (no need to store the energy too).

NiCad packs can (and in some people's opinions should) be discharged to
.8 volts per cell and allowed to cool before recharging. Discharging any
lower than that can cause "cell reversal" which, as I understand it, is
a disadvantageous chemical change.

I use a 1.2 ohm high watt wire wound resistor and watch the voltage with
a multimeter until the .8V/cell mark. I often forget and have ruined a
couple of packs this way. I'm sure some simple zener diode voltage
cutoff circuit would solve the problem but for now, I just discharge the
packs to the .8V/cell level manually. I believe some newer chargers
provide a cycle down and cutoff feature.


Jeff Parisse
www.teslacoil-dot-com





-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com] 
Sent: Wednesday, August 21, 2002 10:50 AM
To: tesla-at-pupman-dot-com
Subject: NiCd Battery Storage


Original poster: "Gary Peterson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>

To the list,

I read that NiCd batterys should be stored uncharged.  Is this still
true for older nicads that have been charged and discharged a number of
times? What about storing a newer battery that has seen only one or two
charge/discharge cycles?

What would be a good proceedure for discharging a battery pack?,
discharge until the output voltage drops off then stop, or continue
discharging until current flow is minimal?

BTW, I use 9 volt nicads for portable operation of a SSTC pulse
generator, and to run a MOSFET driver circuit.

Gary