Battery Tips

[pelkins]

Can anyone point me to a best practices guide to running multiple batteries in an outboard boat?

Thanks in advance

[DaleH]

If not equipped with an isolator, I'd run 2 of the same type betteries off of a 3-way battery switch that has positions for Off, #1, Both, and #2.

I prefer the dual-purpose cranking/deep cycle batteries (I use Exides) in Group 24 size and they're fine for up to V6 OBs to 250hp. Some "newer" motors require specific cranking requirements and you might need Group 27s.

If an odd day of the week, I run on #1 position, and then on #2 if an even day, like today 02May05. I find this keeps the batteries cycled pretty easily. While you can run the OB on "Both" (no harm, it will NOT overcharge one battery with most OB systems) the danger is if you shutdown the motor. If one battery was hotter then the other one was weak, they will equalize. So if on a long run, sure, switch to BOth, but make darn sure to switch to one position or the other once you shut her down.

Best tips for long life is to keep the top of the battery clean, keep connections clean and TIGHT (use nylok nuts ... THROW AWAY any wing-nuts!), and check the electrolyte level every month. Top off with distilled water if/when needed. Keep them regularly charged. One other thing, after charging a battery, if you do not have a load tester, you must wait 2 days for the surface charge to dissipate. Testing otherwise, with hydrometer or a voltmeter, can give you a false sense of their condition.

[pelkins]

Thanks for the feedback. sounds like both batteries should match. Is it possible to run one cranking for startign and one for running accesories?

[uncle4]

Most modern outboard engines have two charging circuits. You can have
one battery dedicated to starting your engine (smaller) and one dedicated to
electronics, trolling motor, etc (larger). The on-board circuitry of the alternator
will charge each battery appropriately (what I do).

Check your outboard owner's manual....

If you don't have dual charging circuits, you can get a balancer/
charger from Cabelas, Pep Boys, etc that'll take the alternator out-
put of your engine and route 2-4 different charging circuits going to
individual batteries.

No reason to keep all the batteries the same: I've got a smaller batter to turn
the engine over, and two larger batteries for electronics.

Uncle 4

[lemaymiami]

If possible get a copy of the current West Marine catalogue. They have a good basic technical advice section for most critical systems on your boat. They'll provide a good starting point for any technical questions you might have. Although I've been rigging my own boats for lots of years now I still refer to their advisories from time to time.... particularly things electrical.

[pelkins]

Thanks for the guidance all I think I am on the road to electrical valhala :brow