You could use a diode as a simple rectifier but I would recommend
using a voltage regulator to stop overcharging the battery.
--- In email@example.com
, "dbuser2" <bawestbrook@...>
> I'm considering replacing a recoil type small engine with an electric
> start engine with a built-in 3 amp alternator. Is there some kind of
> diode or rectifier circuit to allow the engine to charge a small
> lawnmower type battery? The engine has a start switch and solenoid. The
> start switch has an "off" "run" and "start" position. The battery will
> only be charging when the switch is in the "run" position. The charging
> circuit will only need to stop charging when the voltage is around 13.8
> to 14 VDC so it doesn't overcharge.