Dual Battery Questions

Nic_dEntremont

JK Enthusiast
Joined
Nov 21, 2022
Messages
106
Location
West Pubnico, Nova Scotia
Would this solenoid be able to handle being the bridge between two batteries in a simple DIY dual battery system? I found it in a pile of junk at work, it looks new. I found it online and it's 35 amps continuous service.

https://greggdistributors.ca/electrical/Solenoids/col24420

PXL_20230305_231550249.jpg


Also, wouldn't connecting two batteries together make the system 24 volts? Or is that where the difference in connecting batteries in series or in parallel comes into play?

PXL_20230305_231550249.jpg
 
No. You need more like 300 amps continuous, and it should handle 10 minute spikes of around 2500 amps. That's why dual battery systems don't cost $10.

As for voltage, that is exactly where serial and parallel wiring comes into play.

Assume you have two batteries rated at 12V/10Amps.

To connect them in series, you wire the positive terminal of one to the negative terminal of the other. This will deliver 24V/10Amps.

To connect them in parallel, you wire positive to positive and negative to negative. This will deliver 12V/20Amps.

If you wire a dual battery system in your Jeep in series, you will get to do a LOT of other wiring...

On the other hand, wiring them in series is occasionally useful. With your battery, your buddies battery, and two sets of jumper cables you can make the worlds cheapest stick welder. Your choice of rod is limited, but you can toss the cables and rods in your Jeep and it'll work for trail repairs. I've done trail repairs this way. It's not pretty (I'm a crappy welder) but it's better than walking out.
 
No. You need more like 300 amps continuous, and it should handle 10 minute spikes of around 2500 amps. That's why dual battery systems don't cost $10.

As for voltage, that is exactly where serial and parallel wiring comes into play.

Assume you have two batteries rated at 12V/10Amps.

To connect them in series, you wire the positive terminal of one to the negative terminal of the other. This will deliver 24V/10Amps.

To connect them in parallel, you wire positive to positive and negative to negative. This will deliver 12V/20Amps.

If you wire a dual battery system in your Jeep in series, you will get to do a LOT of other wiring...

On the other hand, wiring them in series is occasionally useful. With your battery, your buddies battery, and two sets of jumper cables you can make the worlds cheapest stick welder. Your choice of rod is limited, but you can toss the cables and rods in your Jeep and it'll work for trail repairs. I've done trail repairs this way. It's not pretty (I'm a crappy welder) but it's better than walking out.
Well that makes sense. This thing must have come from a lawn tractor or something lol.

I've seen videos of people welding like that. I'm a welder myself but haven't tried that... Yet.

I suppose I could just carry the other battery with me to jump start the Jeep with jumper cables if needed.
 
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I've seen videos of people welding like that. I'm a welder myself but haven't tried that... Yet.
My welds would probably make you laugh. Or cry. But I make blades, so I'm good at cleaning up the boogers later. Not on the trail, though.
I suppose I could just carry the other battery with me to jump start the Jeep with jumper cables if needed.
I'd carry one of those booster packs for jumping. If you're just looking for self-jumping, a dual battery setup seems overkill.

For trail repairs, I said 'your buddies battery' because I abide by the convention that you don't go wheeling in a single rig. Not on anything other than the easiest of trails, at least. If I'm on a trail that's potentially going to result in damage that would require trail welding, there's no way I'd be alone.
 
My welds would probably make you laugh. Or cry. But I make blades, so I'm good at cleaning up the boogers later. Not on the trail, though.

I'd carry one of those booster packs for jumping. If you're just looking for self-jumping, a dual battery setup seems overkill.

For trail repairs, I said 'your buddies battery' because I abide by the convention that you don't go wheeling in a single rig. Not on anything other than the easiest of trails, at least. If I'm on a trail that's potentially going to result in damage that would require trail welding, there's no way I'd be alone.
Oh you'd be surprised at what passes for welding around here. This area lacks quality standards when it comes to welding.

My main reasoning for setting up a dual battery system is that I got a new battery a while back thinking my battery was the cause of my electrical problems but it wasn't. Now I have a spare battery just sitting around on a battery maintainer.

And I've done most of my off-roading alone until now. I only have one buddy with an off-road capable vehicle willing to go places with brush that scratches paint. I've been places in the Nova Scotia out back, way past where most people would turn around. I wouldn't recommend that to everyone lol.
 
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For jump starting I’d just carry one of those battery packs. Each of our Jeeps have one, they work fantastic. For me part of our basic recovery kit.
I have one. Never needed for my driver, but have used it to help another driver. I prefer them to accidentally blowing up a battery. I seen that happen to my dad long ago, and once to someone I tried to help.
 
I have one. Never needed for my driver, but have used it to help another driver. I prefer them to accidentally blowing up a battery. I seen that happen to my dad long ago, and once to someone I tried to help.
I've never seen a battery blow up but I saw someone melt a post off a battery trying to jump start a truck with a camper battery.
 
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I've never seen a battery blow up but I saw someone melt a post off a battery trying to jump start a truck with a camper battery.
One of our kids is a mechanical engineer. He has a BS, two Masters, and is nearly finished with his PhD.

His wife called me because her car wouldn't start after they tried to jump it. He hooked the jumper cables up backwards...
 
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I've never seen a battery blow up but I saw someone melt a post off a battery trying to jump start a truck with a camper battery.
There is a chance that battery will generate either hydrogen or hydrogen sulfide - I forget which. But if the battery is old and has problems, it can vent gas which is explosive. If the contact, usually ground, is a little loose, then a single spark can become really dramatic. I was taught that you never, ever attach of the jumper cables to the negative terminal of the battery on the car that needs the jump. Attach it to a good metal ground in the engine compartment away from the battery. But you want to be certain that both batteries are in decent physical shape. Both times I saw a battery blow up that grounding rule was violated. The cables were just not long enough to reach a decent ground. Needless to say the engine compartment needs a thorough wash if that happens.
 
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