imho that's not the charger you want .. will charge but very slowly
something like this with adjustable amps and volts
Battery Charger and Engine Starter, 10/2/55 Amp, 6/12 Volt $49.99 harbor freight
http://www.harborfreight.com/10-2-55...ter-66783.html
also you can charge 2 6v batteries together as a 12v