Bonneville America Forums Forums Off Topic Discussion Forums Lounge Any Boaters On Board? Dual Battery Questions.

I was raised boating and since growed have owned 2 outright, a 19' Wellcraft cuddy cabin and a huge honkin' Thompson 21' tri-hull cuddy - a lot of boat in 21 feet. I recently bought a project boat and am re-doing the whole thing. I have decided to go with a 2 battery setup and am wondering how or if a single voltmeter (not an ammeter) works with a dual battery set-up. I'm using the basic "off-1-all-2" perko battery switch. does anyone know if a voltmeter will work? is there anthing to be concerned about while using hte switch? i am under the impression that i can start on one battery and switch to "all" and then the next battery to charge it. what about accessories? what if my fish finder is on and i switch to "all"? will it fry my 12 volt fish finder? any help would be appreciated!

Not a boat but a pickup that I used for a cabover camper. I had a battery isolator that had the high CCA battery connected to just the starter and a deep cycle battery connected to fuse box and thus to everything else. I had both an ampmeter and a voltmeter that was on the line from the alternator and into the isolator. Using two batteries made both of them last a long time. I also had a tiny jumper cable in case I ever ran the deep cycle down to the point where it wouldn’t trip the solenoid.

I had a 1964 Mahogany lapstrake Pembrook cabin cruiser It had a dual Bat set up and a single volt meter set up...No you should not fry your fish finder (although I don't recommend switching batteries with the fish finder on) The all position does not put the batteries in series so their is no voltage increase.

Parallel is how they will run

Parallel (+ to + - to -) = same voltage double capacity (amp hours)
Series (+ to - ) = double voltage same capacity (amp hours)

For a dual batt set up I used to have one "cranking battery" that had the needed CCA (cold cranking amps) to fire the engine and one that had max amp hours (for those long days at anchor waiting for the "big one" to bite while playing the stereo, vhs radio, fish finder all day long...

charge at "all" for the trip home....just be sure your alternator can handle the added load...or charge from shore when you get in...

Pick up a Boaters Bible guide to DC wiring...

connect your volt meter any place after the "out" side of the battery switch...and I had a momentary contact switch in the line so if I wanted to check the voltage a quick push of the button gave me the info I needed...and no nasty "constant draw" oh and keep your zincs freash and pleantiful...

Like this? A boat and a work of art:

EXACTLY like THAT!!

bigger pic

I have a Sea Ray 280 Sundancer with two batteries and a lot of stuff that stays on. You won't create any problem turning through "Both" to the other battery. As a matter of fact, with the engine running (charging), you should NEVER turn the switch through "Off" to the other battery.

They charge best one at a time. The main purpose for the "Both" setting is if batteries are weak and you need help starting. Voltage is the same but it will raise your cranking amps. If out boating or fishing, ride away from home on one battery and back on the other so both will get charged.

thanks guys! excellent advice!! i did a quick read of boat electronics for dummies at boaters world and you guys confirmed their instructions. i also bought 15 things and spent $223! i went in to buy 4 things. saturday i took the wife and son there to buy 5 things which would total $230. i bought 35 items which totaled $560!! boats are fun!! you know what b.o.a.t. stands for? break out another thousand!! seriously tho', thanks again for the "warm and fuzzy". reading it is one thing but hearing it from other folks is a world of difference!!