Hard to tell from the picture, but it seems that is a 12v charger.
If it is, there is NO WAY POSSIBLE to use it to charge
both batteries
at the same time. Don't try it. You'll fry something, and probably more than one thing. There's no problem with swapping one charger between the batteries. It would be a pain, but it works electrically.
If you have TWO chargers, no problem. Just connect one to the front battery and one to the rear battery.
The rear battery charger MUST NOT be connected to the vehicle body anywhere.
There are probably two good ways to connect to the rear (24v) battery:
- Charger + terminal to the 24v buss bar at the back of the engine compartment, and the charger - terminal to the 12v terminal block over near the GP relay. (Yes, that's what I said.)
- Charger + terminal to the 24v buss bar at the + terminal of the rear battery, and the charger - terminal to the - terminal of the rear battery.
Holler if you have questions.