Dual abtteries with a 3rd one on an isolator will it work?

I am new to the boat electical stuff so I DO need a lil help figuring out how to wire in a
3rd battery. I already have a dual battery system and want to add a 3rd battery (with an isolator for charging) for a back up when using electonics, radio/cd palyer, VHF while drift fishing without engine running? Is there a way to wire the 3rd one in as a back up for starting?

Re: Dual abtteries with a 3rd one on an isolator will it work?

I think first you need to tell us a little more about your set up.
First do you have an I/O or an outboard?
Outboards and ONE wire alternators do not work well with battery isolators.
How are the two batteries wired now. Are they wired in series or parallel. Most boats 2 batteries are enough. One for a starter battery and one for electronics and add ons.
If you have a large electric trolling motor then most will use either a very big battery for the trolling motor or 2 batteries for the trolling motor and a separate starting motor battery.

So give us a little more information about your set up and you will get lots of help.
Do you now have a battery switch or vsr.
If you have an outboard what year and size is the motor. How many amps does the charging circuit put out.

Re: Dual abtteries with a 3rd one on an isolator will it work?

here is one way to wire it in

Re: Dual abtteries with a 3rd one on an isolator will it work?

Tailguner said:

here is one way to wire it in

Click to expand...

Better check your wiring. I don't know of many stereos and other accessories that work on 24 volts. If grounded where you show the ground symbol, that is the 24 volt "system" ground and you would get smoke (or at least repeated blown fuses). There are other potential "grounding" issues when there are 12 and 24 volt systems on a boat. Normally 24 volts is dedicated to a trolliing motor and the 24 volt system is dedicated totally to the troller. If one is to operate 12 volt accessories from a 24 volt system, to avoid a potential grounding problem you are strongly advised to wire them to the LEFT battery in the system diagram shown.