I've been reading up on how to determine what size charger is needed. Some things I've read is to take the amp hour rating and multiply by 10%. Based on this, it looks like I would need a 20 amp charger (10 amps per channel - 2 batts). But then I've also read that I wouldn't need a 20 amp charger because I don't need the ability to recharge quickly and that a smaller charger could be used. The reason behind not needing the ability to recharge quickly is because the boat sits idle for a week or so between outings.