Join Date: Mar 2006
Location: Fort Lauderdale
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Going to golf cart batteries is a good idea...if you take a holistic view of your electrical system and your cruising needs. How long do you plan on being away from shore power and how much motoring do you do where the alternator can charge up the batteries? Are you willing/able to simply run the engine to top up the batteries?
*edit*Flooded batteries, which most 6v golf cart batteries are, can be *end edit* a bit of pain as it relates to accepting charge. They do take a good initial charge to get them up from deep discharge, but their internal resistance as charge level goes up gets higher. That means getting them to full charge takes a loooong time...which is tough to do if you're using the engine to power them up. Especially if you have an outboard with an alternator. So you'll probably need a couple of charging mechanisms for these...your alternator and perhaps solar charging.
Speaking of which, even though you have an outboard with an alternator, will your alternator be the right size to keep the charge up on those deep cycles after usage? Two golf cart (6 v set up in series) will give you ~220 Amp Hours (Ah). You really should have four batteries set up in series/parallel because if you have the two 6v battery configuration, if you lose a single battery you've lost your whole bank! So that means with four batteries in series/parallel...thats ~440 Ah of capacity. To keep your batteries charged up, a good rule of thumb is to have an alternator which has output of 25-40% of the size of your battery bank. For you in a series/parallel configuration, thats a minimum of a 100 Amp alternator...somehow, I doubt that your alternator is that large on an outboard that pushes a sailboat...different story on an inboard diesel. BTW - a good 100 Amp alternator is usually in the $600-$700 range from what I've seen.
But wait, there's more! Now that you have such a big battery bank, you'll need to make sure you dont fry those batteries when they're charging from the solar secondary charging mechanism to keep them fully topped up. Now you're talking a regulator too....another set of boat bucks :-)
To be honest, my opinion on golf cart batteries is that its great for cruisers that are away from marinas for days, weeks, if not months on end. If thats the kind of sailing you intend to do, then go for the golf cart batteries....their capacity cant be beat for the price and they're pretty universally available. But if you go that route, dont half ass the installation....otherwise, you'll find yourself needing to buy another set of batteries in a couple of years because the first set never were kept in the right state of charge and prematurely wore out.
Last edited by night0wl; 07-28-2010 at 12:06 PM.