Re: 12V Gel Cell Charger Circuit


From: Arjen Raateland (
Date: Tue Jul 27 1999 - 12:02:48 EDT

Dave Barrett wrote:
> Nice looking circuit, Thanks Arjen


Well, I just corrected the URL.

I had a quick look at the text accompanying the circuit. The maximum
charging voltage is only 13,8 V, and therefore I don't understand what
the 'fuss' with double current limits and time limits is all about.

There is no need to limit the final charging current to 50 mA at that
voltage level. The battery will take care of it. All you need is a
source of regulated voltage 13,8 V with one single current limit (the
maximum initial charging current of your battery). In practice different
batteries may of course require different initial current limits, but
for the rest they should take care of themselves when charged at 13,8 V.
The 4,5 h time limit is a strange idea in this context. It will prevent
heavier batteries from charging at a sensible rate.

A simple lead-acid battery charger can be made with essentially an
ordinary regulator; you shouldn't need to use a special IC for that. The
current limit doesn't need to be very stiff anyway. I presume the MAX
xxx IC wasn't intended for **lead-acid** battery charging, but I can't
confirm this.


73, Arjen, OH2ZAZ

Arjen Raateland
Finnish Environment Institute
SAS Support
phone +358 9 4030 0350

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