Charging batteries

[Surgical_ass]

I've got 2 batteries hooked to an acr system that I just installed. I'm wondering if I hook an external batrery charger to one of the batteries will it:

1. be ok to do?
2. Will it charge both batteries?
3. Should I just unhook and charge the batteries individually?

I hope to install an onboard charger soon.

[MLA]

1) wont hurt anything either way
2) depends on how you have the entire system wired
3) I dont see a need to unhook any battery cables, but again, refer to #2