Battery charger using MOSFET

scribb

I want to build a MOSFET battery charger for 12v lead-acid batteries. Currently, I am using a relay to do the switching; I use a comparator to shut off the relay when the battery voltage reaches a certain level. Can someone give an example of a circuit that uses a series pass MOSFET (instead of the relay)? I plan to have it rated for 3 to 6 amps.

Thank you

KenM

Expensive...IRF4905. Ultra low on resistance.