"Gary" wrote in message ...

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger - what exactly did you mean?

I have rigged up all kinds of circuits as an elec tech, but this would be too risky for me. I would only use a commercial charger and even then would not make any modifications to it. Charging lead-acid batteries always produces hydrogen. Even a little spark or high temp can ignite an explosion which can spray sulfuric acid mist all over. I have never seen an explosion first hand, but have talked to a fellow who is super careful and even he blew one up years ago.

Too many warnings probably, but be sure and connect to the batter first before connecting the charger to the AC source. I also connect the charger to an ext cord, and then (several feet away) connect to the AC receptacle.

FYI, here's a photo of a $25 battery charger I have used for 10+ years. a good investment for other projects.

Battery exploding
http://www.youtube.com/watch?v=d_TnsHu2u4c

Battery getting damaged from improper charging
http://www.youtube.com/watch?v=1APmCDhnuVU

Schumacher 1.5A On-Board Charger Model SE-1-12S. Input 120VAC 4A 60HZ. Output 12VDC 1.5A:
http://imageshack.us/f/205/chargerki.jpg/