Charging an 8 volt battery

Build a circuit to install inline with the battery and then charge with a 12v charger.. ( seies pas regulator.. or zenir shunt regulator.. or even a diode junction based regulator, figuring in forward voltage drop... as your target will be in the 9v range.

Could also hit an electronics supply store and buy a wall transformer / battery eliminator in the 9v range, and slap some gator clips on the end.. or get one of those multi-voltage power adapters that plug into a cig lighter and let you select lower voltages like 9v, 7.5v 6v.. etc.. and use that in conjunction with a 12v charger.. just play with the current settings on the charger and have a vom hooked up to see charge voltage using the 9v setting ont he adapter.

As another poster said.. you need a higher potential at the charge source to get current flow.. thus to fully charge your battery.. you need 9 or just over 9v.. etc.

Soundguy

That all being said (Im an attorney I, love disclaimers lol) I doubt she will charge much if any at all set on the 6 volt range, Sooooo ooo it will most likely have to be set on the 12 to charge at all. HOWEVER, if using the 12 volt I would set her on on a lower charge rate (if the charger is adjustable) plus not leave it on for long periods of time to avoid overcharging and outgassing. I.E. use the 12 setting but dont leave her on too long and keep an eye out for overcharging and bubbling over of acid n outgassing and DO NOT remove the charger leads until AFTER the charger is shut down and shes stabilized and not outgassing them expolsive gasses as a spark (like when cables removed) can ignite them

BE CAREFUL, try it at 6 which I doubt will do anything, so then use 12 which I know will charge her, but use caution n not overcharge or let her run too long cuz if unattended it could eventually harm the battery or worse

John T