Dual Battery Setup

[WadsworthSunsport22V]

Okay, I am completely confused on how my dual battery set up works. I just had two amps, new speakers, and a sub installed in my 07 Sunsport. The installer installed a second battery with a switch. The switch has an off, bat 1, dual, and ba2 position.

Now here is my problem.

1. If I leave the switch in ‘dual’ then both batteries our being drained at the same time, and over time, both batteries will drain each other because of the constant charge/discharge state, when the boat is not running.
2. If I leave the switch in ‘bat 1’ then only battery 1 is being charged.
3. If I leave in the switch in ‘bat 2’ then only battery 2 is being charged.
4. You cannot have the switch pass the off position while the boat is running.

In order for me to go from bat 1 to dual (to charge after starting) then the switch has to pass the off position, which is a no no? So how do I run my stereo with the engine off, then when I am ready to start the boat, be able to switch to bat 1 to start then move to dual to get both batteries to charge?

[lowdrag]

I haven't heard of a switch like that. The ones that I've seen pretty much all go from 1 to both to 2. Does your switch have an alternator field disconnect switch in it or does it have one and your installer just chose not to hook it up? Without having the ability to switch from one setting to another after starting the boat I don't have a good answer for you except to get a different switch and swap them out.

[1986Marauder]

Once your engine is running you should be able to turn the switch to off and then dual w/ out the motor dying. Your alternator will keep the motor running then charge both batteries when set to dual on the switch. If your motor dies they wired the switch incorrectly.

[lowdrag]

Do not turn the switch to the off position while the engine is running unless you are sure you have an alternator field disconnect switch in your battery switch and know that it is hooked up. If the alternator is charging and it has no battery to absorb the charge you will damage it. The field disconnect keeps the alternator from producing a charge when you switch batteries.

[IndyMatt]

I honestly wouldnt mess with the settings, leave it on dual, that way you access the full potential of the dual battery system. Electrical voltage follows the pathways of least resistance, so as the primary battery drains, the secondary will deliver charge as long as available voltage is greater than the primary. The reverse will be true when the alternator is charging the batteries. I think you run a greater risk by moving the switch around. Certainly dont switch the batteries off while the motor is running or you will isolate a ground loop- available charge will be backed up through a ground and damage electrical equipment. If you are worried about running your stereo without the motor running, purchase a priority start battery isolater (around $30) and install it on the second battery, that way you wont run your system down below available cold crank. Good luck.