Generator
Franklin,You do need some additional information. You need to know the capacity of the batteries. It is expressed in amp hours or we can make a pretty good estimation if you can give us the size. Size is not voltage, but rather Group 24, Group 27, Group 4D, etc.Also, with that large a generator you will want a larger charger than you currently are getting. Dump the automotive charger. The 40 amp is fine for most recharge events, except when you want to minimize generator time and have a fairly large discharge. Also, make sure the 40 amp is a good three stage charger. If not, dump it and get a good inverter/charger that puts out around 100 amps charge.I disagree with a bit of the advice here. Rather than using 50% of battery capacity before recharge time, you need to think in terms of 35% (sucks huh?). The reason is that you do not want to discharge your batteries beyond 50% (hence their 50% advice), but, that is only valid on the first discharge from a full charge. After that, on the generator, you will probably only want to run it until your charge parameters equal about 85% of fully charged. This is because the last 15% takes too long except on shore power because the charge rate tapers faily dramatically at that point. So, after the first discharge, you are subsequently working on a 35% range.What does this mean? If you have two Group 4D batteries like we do, then you get 200 amp hours of use the first discharge. After that you get 140 amp hours between recharge events with the generator or engine driven alternator (assuning you take them up to 85% each recharge).Hope this incrementally helps.Dan Jonas (S/V Feije II)