wiring/battery question

[Scoot]

I bought a used boat that I've had TONS of electrical problems with. I can't figure it out. Poor Marine_Man has been very helpful and has walked me through dozens of questions and answers.

The latest question is this- there's a wire running from my trolling motor batteries to my starting battery. I have no idea why this is there??? There's a 2 bank charger on the trolling motor batteries, so it's not for charging all three batteries. Any ideas why they'd be connected?

[ATW]

Is the wire just connecting the neg post on the starter battery to the neg post on the TM battery (or just the one most neg post on a 24v TM system)? This is done to provide a common negative reference that can help to reduce electrical noise on your electronics. There's no harm in removing the wire if you want.

Paul

[marine_man]

ATW might be right on with that..

Is there only one wire (black? red? how big?) or are there two?

marine_man

[Scoot]

I'm at work now, so I can't say for sure, but I'm pretty sure there's both a positive (red wire on the + terminal) and a negative (black wire on the - terminal).

[marine_man]

Are you sure it's connected to your starting battery?

Do you by chance have a trolling motor receptacle at the back of your boat, and these wires run from there to the trolling motor batteries in front?

marine_man

[Scoot]

It sure didn't look like it. There's a bajillion wires though... I'll follow them along again tonight and make sure that my description of the wiring was correct.

[marine_man]

One other question is how large of a wire are they? Trolling motor size? Smaller, more like an accessory size?

If the wires are connected from the trolling motor batteries to the starting batteries I'd disconnect them on both sides.

marine_man

[Giant_Jackpot]

Could it be possible that they were trying to charge the trolling batteries from the main battery? This generally does not work very well ………

[Bassboy1645]

If I remeber high shcool shop class a yr ago parellel is same voltage 2 batteires right?? THen in theory you could hook up the batteries in parelle and charge 2 at one time?? plz correct me if im wrong.

[marine_man]

Yes.. you're correct.. positive to positive and negative to negative is parallel.

The issue is that not only are you charging both batteries at once, you're also drawing both batteries down at the same time - so in theory, you could run your trolling motor all day and drain your deep cycles and your starting battery without ever knowing it.

marine_man

[Bassboy1645]

I was wondering about 2 deep cycles...I have 2 up front for one motor but its a 12 volt and I was thinking of charging them both at the same time when I put her in for the night??