Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!ogicse!milton!sumax!polari!miker
From: miker@polari.UUCP (Mike Ranta)
Newsgroups: sci.electronics
Subject: Re: Charging Nicads
Message-ID: <4621@polari.UUCP>
Date: 30 Jun 91 00:21:17 GMT
References: <51309@ut-emx.uucp>
Distribution: usa
Organization: Seattle Online Public Unix (206) 328-4944
Lines: 16

>The discussion of charging nicads makes it sound as though a simple
>power supply regulated to about 1.4 volts would be an excellent
>battery charger.  Is that correct?

No, this isn't correct.  It will charge them to a point, but nowhere
near full charge.  Also, depeding on the type of regulation, the
initial current may be way too high.  The cutoff voltage of Nicads
when charging is somewhere around 1.5 - 1.7 volts per cell depending
on the cell and the charging current.  Interestingly, this voltage
actually peaks and STARTS BACK DOWN if you leave the cell on charge
too long.  This is how the most elaborate (and best) chargers work.
They're called "peak detecting" chargers and the automatically
correct for cell aging, ambient temp, and the type of cell.  The
voltage drops because once the cell is fully charged the temp of
the cell starts to rise which causes a subtle drop in voltage (wierd
but true).