🚀 go-pugleaf

In article <985@eplunix.UUCP>, raoul@eplunix.UUCP (Nico Garcia) writes:
> In article <5664@uafhp.uark.edu>, bbs00068@uafcseg.uucp (Joel Kolstad) writes:
> >[questions about gel cells]

> Hmmm. I won't address your NiCad questions, since I've never worked with 
> those directly. However, for a Gel-Cell charger, use a LM317 rated for
> your maximum voltage from your power supply to provide a regulated 
> charge voltage, and drop a resistor on the output of it to limit the current
> to your batteries. You only need a trickle charge anyway, and a 12 Volt
> supply, even if you put the battery in backwards, will only put a 24 Volt
> drain on it. Put a 1 K resistor there, and a diode to stop discharges,
> and you win.

Sorry, accidentally sent this off before checking your power demands.
For a 12 Volt supply, with a 10 mAH drain once per hour, you want a recharge
of oh, say, 100 mA to charge quickly: and 1/10 your maximum AH capacity
as recharge current is 100 mA for 1 AH gel-cells. So, figure a mimimum 
1 Volt differential, and a 10 Amp resistor is needed. 12 Volts for
a completely discharged battery, and you get almost 15 watts heat 
dissipation. Gaah, a bit large. You could use a second LM317 as a 
current limiter. The National books have good application notes on 
this. Depends on your size and circuitry constraints. Don't forget 
a 3-Volt drop and minimum currents for good regulation.

I've had very good luck with gel-cells left on trickle charge. The Yuasa
12-Volt 0.8 AH have behaved very well, even if their connectors are a bit
weird.
-- 
			Nico Garcia
			Designs by Geniuses for use by Idiots
			eplunix!cirl!raoul@eddie.mit.edu