Wiring a 3rd battery?

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5Cruiser

5Cruiser

Joined
Sep 12, 2010
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Colorado
Feel free to move this if I should post it elsewhere, but I have a 100.

I have two batteries up front with a nat. luna isolator.

I am exploring adding a third battery and having the following set up.

two batteries up front working "in line?" such that one drains first, then the second. I'd like a simple cut-off mechanism that stops from drawing power from the second without a manual over-ride, but I'm talking very simple isolation. For the third battery, I would want it to function as the "second" on the other side of the nat. luna isolator.

The thought is that the two tandem batteries would run the truck, winch and all accessories. The third alone one would be just for the fridge.

I need to learn about battery systems and isolation. Suggestions of where to go, threads or builds to read, etc, etc? Primarily about three battery systems. I also want to explore solar to help trickle charge the fridge battery during the day.

I'm in the middle of a major rebuild of my rear cargo kitchen right now and there could be a spot for a battery by the fridge.

Thanks.
 
Pretty simple, run a #10 or heavier wire from the + of your main batteries to the kitchen area battery, use a thermal breaker and solenoid wired to ignition hot for control. Locate the breaker as close to the +12 supply connection as possible. This is the exact system used to charge trailer batteries.

I'm not sure what you are trying to do with the two main batteries.
 
What Dan said about wiring it up same as a trailer/RV system. If you want to explore the solar thing, here are a couple of sites that may help with the design/equipment. The first is complete kit that would supplement charging the fridge battery. The second site is an FAQ about RV solar systems.

RV,Van, Marine Kit With 140 Watts of DC Power

RV Solar Systems
 
rusty_tlc said:
I'm not sure what you are trying to do with the two main batteries.
Click to expand...
I've got the two isolated batteries. The starting one has been run down before and I had to jump it from the other battery. This is the big reason for having two. However, I have also run down the second one before with the fridge. I fear both occurring at the same time. I want the third as a real backup. However, I figure having two tied together to handle the truck and accessories was the better way to go, then have the other battery at the back isolated with the nat. luna and serving only the fridge.

Sandroad said:
What Dan said about wiring it up same as a trailer/RV system. If you want to explore the solar thing, here are a couple of sites that may help with the design/equipment. The first is complete kit that would supplement charging the fridge battery. The second site is an FAQ about RV solar systems.
Click to expand...

Thanks, I'll check these out. Solar is the backup for the solo battery for the fridge.
 
5Cruiser said:
I've got the two isolated batteries. The starting one has been run down before and I had to jump it from the other battery. This is the big reason for having two. However, I have also run down the second one before with the fridge. I fear both occurring at the same time. I want the third as a real backup. However, I figure having two tied together to handle the truck and accessories was the better way to go, then have the other battery at the back isolated with the nat. luna and serving only the fridge.



Thanks, I'll check these out. Solar is the backup for the solo battery for the fridge.
Click to expand...
I'd set up the third battery as I described and leave the isolator in place. With the fridge on it's own source you shouldn't have any draw on the aux battery when the truck is off.

If you want to use the third as a jump start battery set it up for easy removal, you really don't want to run a heavy gauge wire from the back to the front for starting.
 
rusty_tlc said:
Pretty simple, run a #10 or heavier wire from the + of your main batteries to the kitchen area battery, use a thermal breaker and solenoid wired to ignition hot for control. Locate the breaker as close to the +12 supply connection as possible. This is the exact system used to charge trailer batteries.
Click to expand...

Oh, okay, I think I'm starting to understand you. This does sound smart...uh...but I still don't understand.

So I do not connect a negative to the main battery? I only connect a positive and then ground the negative on the fridge battery?

So this will charge the fridge battery when the car is running, but will not provide power to the main if it were to die?

This would leave the second battery virtually unused, unless I needed to jump the main, or link the two together for winching though the luna features. That is good.

As I write this light bulbs are coming on all around me. This is making a lot of sense if I am understanding.

Can you please tell me more about the thermal breaker and solenoid?
 
For stuff like lights and the fridge you can get away with a ground to the frame or chassis, there is a body ground point near the center of the rear cross member.
For a remote ham radio install I would run a ground directly to the battery to avoid electronic noise, but that is another topic;).

A thermal breaker will protect the wire from the main battery to the rear battery, after an overload it will auto reset when it cools down, if the excess load is still there it will trip again. You want it as close to possible to the main battery because the wire from the supply to the breaker can potentially carry a lot of current and get very hot.

A solenoid is a switch that is activated by a voltage from the vehicle, it has three terminals; in, out and control (connected to a circuit marked accessory). You want one intended for continuous use. The best thing is to go to a trailer place, RV or otherwise, and ask them to help you. I've actually found the places that sell flatbed and horse or cargo trailers to be more helpful than RV places YMMV.
 
^^Thanks for the advice, Dan, really appreciate it.

Talking to a trailer supplier would be a good idea, probably have the electronic parts I need too.
 
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