how to operate battery switches?

[pvan]

I looked but did not find how my battery switches work? I have three total 12v marine batteries.
I have two switches: one that has off, batt1, batt2, and both
\the other switch has on or off

how do the switches work and when is the inverter charging the batts and when is the boat 12v running only off the inverter that is plugged into shore power?
thanks in advance :smt021

 

[trflgrl]

Trace your wires to be certain, but....

Most likely the switch with on/off settings controls a single battery that starts one of the engines and possibly some other critical items. The other switch controls the remaining pair of batteries: setting 1 means you're starting the other engine/running house systems on one of the pair, setting 2 means you're starting/running off the other, and setting both means you're starting/running from both. You probably have a dash switch labeled "emergency start" or something similar, as well--that ties the two banks together (think jumper cables) in case one side or the other is too weak to start its designated engine.

It's a really good idea to map what each switch setting does for you, so you can get into a power management routine. Turn both switches to the off position. Then turn on the on/off switch and assess what systems work--try to start each engine (and generator if you have one), turn on every cockpit, dash, and cabin switch, and so on; check the fridge and any other straight-wired appliances, as well. Then turn off that switch and turn the other to position 1 and run through the same thing starting engines/genny, flipping light switches, etc. Move it to position 2 and repeat, then position both (theoretically, there should be no difference in what runs with this switch in 1, 2, or both, but it's good to know for sure!).

Assuming factory wiring, the AC converter is charging the batteries while you're on shore power....while the batteries are running 12v systems.

If you have an inverter also (including a combo converter/inverter), it can power 120v systems from the 12v batteries when you're not on shore power.

HTH!!

 

[FireDrill]

Not sure if you have the same setup I do (94 Sundancer 290 with two batteries), but here's how someone explained using the battery switch to me:

When docked on shore power, turn the switch to Off, as you don't need the batteries and they'll charge even when "Off." Turn the switch to either 1 or 2 (doesn't matter) to start the the engine. If you anchor and need battery power, turn the switch to the other battery - this leaves the first battery charged so you can re-start when you're ready to get moving again. When youre ready to pull the anchor and get cruising again, switch it back to the first battery (the one you first started the engine with), and you should be good to go.

I'm sure there are other details and more technical ways of describing this, but the above has worked for me - both batteries stay sufficiently charged, and everything works. On my boat, both batteries seem to be wired in to the entire electrical system, and so everything works no matter which battery is "on." It's as if changing the battery switch from 1 to 2 is like moving a plug at home from one outlets to the other.

 

[pvan]

thanks for your input guys I did as suggested and did testing. Seems when I unplug from shore power batt 1 runs stereo and other 12v stuff but only starts starboard engine, Batt 2 same but only starts port engine and when both is switched both engines will start and all 12v stuff operates

the on off switch is only for emergency start switch so if other two die you can use the third batt to get engines going, does this sound right as boat is factory wired with the two switches and three batteries.