For lead-acid chemistry? Have a look at the TI UC3906 data sheet and
the ap note for that part. You just need to provide the pass
controller capable of 20 amps. I've been toying with using that part
to control a switching circuit to keep efficiency high and power
dissipation low, but haven't actually tried it yet. The controller IC
does a good job, though. I've used them in lower-power linear-pass
circuits.

Cheers,
Tom

David Carrick wrote in message . ..
Looking for a circuit for a 12 volt three stage 20 amp battery
charger.