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4 hefty marine deep cycle boys. Think he used to have solar on the roof (whole thing) but it would really only sort of charge one of them, so now he just charges it at home before every trip, if trip longer than a few days either plugs into shore power at whatever race he's at, or drives around a bit, even with a larger alternator it doesn't really do much to batteries unless you drive for 4 hours +
No leisure battery? Any decent sized fan is going to significantly eat into the starter battery if it's running for more than a few hours.
That must be a huge set of batteries.