I was thinking bout an on board charger but I'm nervous about ventilation also. Whenever I stick my head into the battery compartment, you have to be a contortionist to do so, I get some minor fumes. I'm sure it'd be fine, but I have considered putting in a vent fan that engages when the charger is plugged in, but then I'd have to deal with the issues having a small fan would introduce. Though I'm probably just being overly cautious. I was looking at these chargers (
Dual Pro Charger On-Board Battery Chargers - XL Series) or these (
Bass Pro Shops XPS i Series Advantage On-Board Marine Battery Chargers) they seem to get decent reviews and have the best bang for the buck.