battery wiring

[state of mind]

I have an '88 30' Sundancer. There are 3 batteries, one on/off switch and one 3 position switch (off, 1, both, 2). I'm struggleing to find out what battery does what. One should be a house battery but so far it's not obvious. My next step is to start disconnecting wires and see what works/doesn't work. Any comments or suggestions? :huh:

 

[Iprof]

Mine is set up with #1 being the starting battery and the other 2 batteries are #2 for the house. I also have my generator set to start off of the #1 battery. I replaced the two 12V house batteries last year with 2- 235 amp 6v Golf Cart batteries from Interstate. It's great having all that power when at anchor, we get about 18 hours out of the batteries before we have to recharge.

Ken

 

[JVM225]

One of my batteries starts the port engine.
The other two start the starboard engine and power the lights, accesserioes, etc.
With everything off, loosen the wing nuts on the three batteries to just barely thumb tight.
Disconnect the negative side of one battery, then try to crank the port motor. Continue taking off the negative cable from each of the three batteries until the port motor won't crank. That will be the one for the port motor.
Repeat the process for the starboard motor, accessories, etc..
Draw a little diagram after you have them all figured out, and keep it on the boat.

 

[CaptianWilly]

I have the similar 3 battery setup on my '89 230CC. Position #1 is the starting battery and position #2 is the pair of deep cycle house batteries hooked up in parellel. My question?...with the switch in position 'both', does the alternator charge all 3 batteries effectively or do I need to charge the starting battery separately from the house batteries? I have a 100 amp alternator. Is a charge isolator required to charge all three batteries properly when underway?

I know it's a lot of questions but any help would be greatly appreciated. Thank you

Bill

 

[andyr]

There is a thread about this in the maintenance forum last week.
You should have the third battery on a separate switch, isolated and charge periodically. Charging 3 batteries off one alternator should have a charge isolator.

 

[JVM225]

Although I know what battery starts which engine, I'm still confused about the battery switch.
It is a typical 1,2, Both, and Off switch.
I have two motors, with two alternators, and three batteries.
If the switch is set to off, nothing starts, and no 12 Volt stuff comes on (Except bilge pumps).
If the switch is set to any of the other three settings, both motors will start and all 12 volt stuff will work.
I could understand the switch if I only had one motor and alternator with two batteries. That would probably mean that Battery 1 would charge from the single alternator when that battery is selected on the switch, Battery 2 when that one is selected, and both if I made that choice.
But with two engines and alternators, I don't understand the set-up.
Anyone?

 

[Cincy Aquaholic]

This is an interesting thread because it made me realize I'm not entirely sure how mine work either and my manual is of no help. I have a similar set up, 2 engines, 3 batteries but I have THREE switches.

1) typical 1,2, both, or off.
2) on and off
3) on and "off at detents" ???

what is that? Truthfully I never switch them from both, on, on.

Seems that you should always be able to isolate the generator or one engine battery so you can be sure to be able to recharge.

 

[Ka1oxd]

I will add to the mix. I have two switches, on and off, and three batteries. From what I got one switch for the port, 1 battery, and one switch for the starboard and two batteries.