12v GEL battery charging

[CptClinac]

Hi guys,
I've also done quite a bit with gel batts. I disagree with Evil Twin regarding charge voltage.
The slightly different chemistry of the gel battery shold not be charged to the same max voltage. In Pb-Acid batts this is 13.4 through to 14.4 V absolute max. In gel this should be reduced to 13.2 to 13.6 V.
Most cheapo chargers allow the battery to overcharge at 'trickle' (up to 16V at very low current) where gasing will happen. Not too much prob as water can be replaced. On sealed batteries this IS a problem. On gel batteries this is even more of a problem.

If your car alternator is set to definitely no more than 13.6 V you can connect it OK. Watch out for excess charge current heating the battery. (ie don't try putting a small gell cell on a 150A alternator).

A cunning ploy to charge the gel from a slightly higher V alternator is to fit a silicon diode of sufficient current rating in series. Each diode drops aprox 0.6V. You can pick 10A diodes from Jaycar etc. This would allow a 14.2V system to be used to supply 13.6max.

Bare solar chargers are much the same as the cheapo chargers. I have put a regulator on my solar-gel system.
My solar charger claims to be suitable for automotive top-up and has a max V of around 18V ! ! ! ! !