Any ideas on charging 12v battery on fl250?

[mazdarx7s2]

I have an 83 fl250 and i would like to add a 12v deep cycle battery to power a cooling fan and HID lights.
I have a battery, fan and lights, only problem is finding a way to charge the battery.

I have tried converting the lamp coil out put to a floating ground to convert the current to DC using a bridge rectifier, however i only get 2v.
coil will run standard lights using AC, so i am assuming it is working correctly.

any ideas? how do the electric start kits charge the battery?

[1978flcod]

you can get a rotortiller v drive pully for a y belt for rear axl and just use automotive alternater

[copper204]

Try to find a wiring diagram of the Goki electric start? it has a charging circuit built into it that uses the lighting coil.?