This charger can charge almost any battery type at any voltage. It desulfates lead acid batteries as well. It works quite well. Be warned tho, it contains lethal voltages. If powered by 120vac it can get up to 170 volts and 340 volts on 220vac.
Step 1: Materials:
Ac run capacitor
Rectifier or 4 diodes
As you can see it is quite simple. The capacitor couples the battery to the mains as well as limiting the current. At 120vac it charges at 1 amp for ever 22uf in capacitance, 13 uf at 240. The switch is merely convenience so i dont have to unplug and replug. Then the diode bridge rectifies it to dc.
Step 4: Usage
it works in a way that if the battery is sulfated or weak etc. it will always charge at the preset amps. So if the battery is only taking 5 amps at 12 volts and u have it set for 10 amps, it will raise its voltage until it is charging at 10 amps. At 120vac the charging voltage could go up to 170vdc. 340 with 240. It also pulses at 120 herts which desulfates the lead acid batteries. It should also be noted that this is a universal charger and will charge any voltage battery. It should also be noted that the is no protection against over charging and if it is left on the charger when the battery is already charged it could damage the battery.