Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!samsung!think!eplunix!raoul
From: raoul@eplunix.UUCP (Otero)
Newsgroups: sci.electronics
Subject: Re: battery chargers
Message-ID: <808@eplunix.UUCP>
Date: 2 Dec 89 21:05:09 GMT
References: <28220@amdcad.AMD.COM>
Organization: Eaton-Peabody Lab, Boston, MA
Lines: 31

In article <28220@amdcad.AMD.COM>, phil@diablo.amd.com writes:
> I just found a source of 12 V 6 AH sealed no maintenance lead acid
> batteries for $10 each. They seem to have a lot of applications (house
> burglar alarm, CB radio power, video camera and lights, etc) so I am
> looking for some advice on what a charger needs to do. What is an
> appropriate fast charge rate? Is it ok to trickle charge them in a
> burglar alarm application? What does the discharge curve look like?
> How should a fast charger know when to turn off? Do lead acids have
> the memory problems of NiCads? Is it ok to leave them flat? What is
> the best condition to store them in? 

Yuasa batteries has an excellent catalog, data sheets, and source of
information on how to treat sealed lead-acid batteries. Call them at
(800) 423-4667 or (800) 962-1287 for it. 

In general, recharge at a constant current of <1/10th the AH rating.
Put a diode between the battery and your charger to prevent accidental
discharge, and make sure your maximum charging voltage is limited as
well. A CVCC (constant voltage constant current) recharger is your
best bet. There is an excellent recharging circuit shown in the National
Semiconductor data books for the LM317 and LM337 voltage regulators.
Just make sure your heat sink is big enough as well. If you send me
an address, I'll send you a diagram of the automatic recharging
circuit I set up for some medical instruments here. Don't leave them
flat, and do leave them charged in a cool well-ventilated place. They
don't have Ni-Cads memory problems, fortunately. Trickle charging should
not hurt a sealed lead-acid. 
-- 
			Nico Garcia
			Designs by Geniuses for use by Idiots
			eplunix!cirl!raoul@eddie.mit.edu


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