Dual battery, general DC wiring

[fender22]

Fitting a dual battery system. Already have a 2 way switch fitted but one battery. I imagine there are markings on the switch as too what goes where but essentially when both batteries are selected does it put them in paralel or series?

I will also be running a few lights on the same circuit off the same switch. Again to they run in parallel or series? I know if you wire in series in AC the voltage is shared between the two lights and I thought it was the opposite way around with DC?

Many thanks in advance...

[BM]

When you switch the switch to "both' it parallels the batteries. If it series connected them you would have 24V and blow the equipment.

Heres how to wire a battery switch:

Engine cable goes to the "common" terminal

The pos from one battery goes to the "1" terminal and the other batteries pos goes to the "2" terminal.

The negs on the batteries are connected via a cable running from oe battery directly to the other.

[Jaffo]

If you put to 12 v batteries in series you will have 24v. Best running in parallel as you will have 12v to all that is connected. If you wish me to explane in more detail send me a pm for my phone number.

[fender22]

Thanks guys. I assume when you say wire the engine cable to the common you mean engine cable and lights, accessory power also?

When you switch the switch to "both' it parallels the batteries. If it series connected them you would have 24V and blow the equipment.

Heres how to wire a battery switch:

Engine cable goes to the "common" terminal

The pos from one battery goes to the "1" terminal and the other batteries pos goes to the "2" terminal.

The negs on the batteries are connected via a cable running from oe battery directly to the other.

[dnej]

Fender 22,
I use two isolation switches,a little different to most,but excellent to use.
Basically,one switch is used to connect to the other,only when an emergency start is needed.

Other than that, the start battery is just that,and the second battery is for the electronics,but will be there, when needed.
Just follow the diagram,and you will nut it out.
Regards David

[BM]

Most changeover switches have a terminal marked "common" or you could say "output" also. Yes, your power cable for your onboard equipment will run fromt he common terminal also or if you planned a dedicated house battery then it would wire directly to that battery. There would need to then be a switch installed in that cable to isolate the house battery.

[dnej]

BM,in my diagram,by using a second isolation switch,you can use the dedicated house battery,and connect it to the motor,via the second switch,to use for an emergency start.
David

[fender22]

I will only be using the single dual switch, but from your diagram you link the negative of both batteries together? Is that correct?

And from there out to the negative terminals of accessories, motor etc?

[finga]

This may help

[dnej]

Fender 22,Finga answered that for you,so yes is the answer.Just make sure if you are travelling,that you switch to both,before changing through to an alternate battery.In that way one battery is always on line.

The trouble with only one switch,is that both the accessories,and the motor ,are still one the one battery,as Finga has shown.

I like to keep my electronic gear away,from the motor. Isolation switches are relatively in expensive these days
David