Battery management

[drynoc]

I'm coming back to my roots to get a battery management question answered. I tried on a power boat forum, but that answers have been slow coming. I know someone here will know the answer.

My new boat has two engines and two batteries, but only one battery switch. The owner's manual says never to operate it with the switch in the "both" position. The question then is, how do you operate it? And what is the purpose of the switch if each engine has its own battery? That set up is similar to a car, where the engine takes care of its own battery. I can see the need for a switch that would switch batteries between engines, but this is a standard "off-1-both-2" switch. I can see some utility for the switch in the use of the DC accessories, but not with regard to starting and operating the engines.

Thanks for the help.

[sailingdog]

It is hard to say without knowing more about how the stinkpot is wired.

It may be that if you operate it with the switch in the both position, the two alternators will be trying to charge the batteries, and the voltage from one may confuse the voltage regulator in the other, resulting in neither charging the batteries properly.

[Delirious]

I'm guessing you also have two alternators and so each battery is directly wired to it's own alternator and possibly voltage regulator without passing through the switch. Running on "Both" would have the regulators "seeing" each other and, if there are seperate voltage regulators, thinking the system didn't need full charge and dropping out. (What he said above).

You need a seperate starting battery for each engine and a house bank to carry the loads when the motors aren't running . . . if that ever happens on one if those boats. ;-)

[gc1111]

If we assume that the two systems are identical (i.e. each has the same alternator, battery and starter setup) and the 1-2-both battery switch has leg 1 going to one system, leg 2 going to the other, then the question is where does leg 3 go?
When the switch is in the both position, it connects the two and allows you to start an engine that has a dead battery from the other battery. But depending on where leg 3 goes it might have other uses.

[k1vsk]

I can understand why your question on another forum generated few responses - it's pure supposition to try to discern what the switch does without knowing/seeing the schematic. If you can attach the wiring diagram or explain how the system is wired, the answer may be self-evident.

[SteveInMD]

I suggest removing one engine, and buying a mast and some sails. This will simplify the wiring considerably.

[bubb2]

Originally Posted by SteveInMD

I suggest removing one engine, and buying a mast and some sails. This will simplify the wiring considerably.

Brilliant!!!!!!

[artbyjody]

Just a guess - but the third wire is most likely to the generator if you have one installed. Better than asking us "where does it go" why not trace it down?

[SEMIJim]

Originally Posted by SteveInMD

I suggest removing one engine, and buying a mast and some sails. This will simplify the wiring considerably.

I don't get it. Won't he just go in a circle, then?

Jim

[JHJensen]

Originally Posted by drynoc

I'm coming back to my roots to get a battery management question answered. I tried on a power boat forum, but that answers have been slow coming. I know someone here will know the answer.

My new boat has two engines and two batteries, but only one battery switch. The owner's manual says never to operate it with the switch in the "both" position. The question then is, how do you operate it? And what is the purpose of the switch if each engine has its own battery? That set up is similar to a car, where the engine takes care of its own battery. I can see the need for a switch that would switch batteries between engines, but this is a standard "off-1-both-2" switch. I can see some utility for the switch in the use of the DC accessories, but not with regard to starting and operating the engines.

Thanks for the help.

Drynoc,

I am assuming the vessel you are asking about is the 1999 Formula 330 SS listed in your previous posts. (nice boat by the way!) On your behalf I put a call into Formula. You should call 260-724-1412 tech help…..Speak to John in tech support and he should be able to answer your question plus provide you with any needed documentation. In the past I have found this company to be most helpful.

Jhj

If the vessel in question is not the one I posted.. list it here or PM me and I will see what we can do.

Additonal to folks.... when you ask a question about a boat, please tell what kind.....even if you have gone over to the dark side.