Battery switch and house battery

C-Dawg · Posted: Thu Apr 16, 2009 1:16 pm Post subject: Battery switch and house battery

I'm getting my ducks in a row to add a house battery. I plan to put a group 24 AGM and a battery charger under the galley. The charger will be powered by the onshore power system to be installed, also.

I read some old threads, but didn't see a couple of things answered.

So, first question: where did others put their battery switch? I'd like to keep it as accessible as possible from either in or out of the boat. Is the splashwell okay with the terminals inside the starboard lazzarette?

But it would also be nice to have it near the battery charger so I can put the charge leads on it; would save running some wire.

Second: anyone have a good schematic of how their boat is wired with dual batteries? Cranking and house batteries, one big motor and kicker.

Thanks.

Sea Wolf

NewMoon · Posted: Thu Apr 16, 2009 5:51 pm Post subject:

Hi C-Dawg,

I have a diagram of such a setup. It's a little different, since the diesel engine has a separate alternator and regulator, and there's a Link amp-hour meter, but it should be pretty easy to understand and modify to your needs. It's a Word document, using the simple drawing tools. Post or send your email address and I'll send to you. Mine's newmoon1@prodigy.net

thataway · Posted: Thu Apr 16, 2009 6:15 pm Post subject:

You want to keep the heavy duty (00) cables to a minumum--and the charging wires will only be 5 to 10 amps, so they can be #10--or even #12 on a C Dory 22. Thus it is better to have both batteries near both the switch and the engine.

You run the 00 cables from the battery to the switch, -the engine start to #1 and house to #2. You put each battery charger positive to the same terminal or to the battery. You put the "output" of the switch to the engine start and circuits of the boat. This way you can use all, 1 or 2. It is best to have a "Make before break" switch--this way the alternator is always connected to a battery and there is no risk of blowing the diodes.

The stove and bilge pump will be directly connected to one of the batteries--and fused appropiately.

For the most part, outboards do not have a fuse between the engine and the battery--all other circuits are fused within 7" as Joe noted.

Capital Sea · Posted: Thu Apr 16, 2009 7:14 pm Post subject:

Put the charger under the heater and the house battery under there as well. You should get advice from Aaron at Fife SeaRay if you are going with sealed Gel batteries as he was able to work out the switching, breaker and such, so the system works well with two different size batteries. The switch is such that the only time you will ever want to change its setting is when the crank or house battery is dead. I have never had that situation. The outboards, charge the crank battery first and then the house battery. Also, I had a gage installed on the dash along with an A/B switch, so I can check charge status at the touch of a finger.
There is a thread that shows how to set up shore power with a GFI protected extension cord mounted under the sink and wired into a bulkhead pass through exiting up under the valance to the storage shelf outside the cabin, where it is protected from rain. You plug the charger into the GFI outlet and have another outlet for misc electrical devices while the boat is plugged in. When parked on land, my dehumidifier plugs in here.

Got my kicker servo system in the mail today, so back at ya my friend.

thataway · Posted: Fri Apr 17, 2009 4:12 pm Post subject:

I suspect that Captain Steve means AGM battery, rather than Gel cell. The charging voltage of the outboard's relitatively poor regulation will damage Gel cells.

Chuck S · Posted: Fri Apr 17, 2009 6:59 pm Post subject:

Takes very little amperage to start a Honda 50. I don't recall the amps, but I've got one battery on my 16 Criiser and it's a Group 24 deep cycle. Not dual purpose starting/deep cycle. Seems to be handling the small load just fine. I'd think a pair of deep cycles would work just fine with twin 50s.

On my auxillary powered sail boats with two house and starting batteries I just ran the battery charger to the same place on the Off-1-Both-2 switch that the alternator connected. With isolation both batteries would charge off the engine or off the batery charger when idle. Heck, they'd charge with the battery switch in the OFF position without harming the alternator.

-- Chuck

C-Dawg · Posted: Fri Apr 17, 2009 11:21 pm Post subject:

Since Boater's World is having their going-out-fo-business sale, they have marine wire at 50% off. They have enough 2 AWG for me to do the job; is that big enough to run about 10-12' from house battery to switch?

The next size they had was 1/0 and it seemed way too big for the job.

Capital Sea · Posted: Sat Apr 18, 2009 7:26 pm Post subject:

Both Batteries are Optima Bluetop sealed marine multi purpose.

thataway · Posted: Sat Apr 18, 2009 10:46 pm Post subject:

C Dawg,
You probably can get by with #2. The distance is the total distance or 20 to 24 feet--not 10 feet for calculations. You will get about 6% voltage drop with the #2--to get only 3% drop you could draw no more than 120 amps (not sure what power your outboard draws).