How to make a cheap isolated dual-battery setup for $50

[dlichterman]

Ok, so I wired up a house battery as per instructions.

Before I connected the positive cable from the solenoid to the truck battery I checked the continuity (ignition off) across the solenoid and it was open (as it should be). When I connect to the truck battery I get continuity across the solenoid (ignition off). Doesn't seem right or is it?

Can you be more specific? Are you talking about the 2 main poles or the power coming in to engage the solenoid?

 

[Bintang]

I was talking about the main poles (large terminals) on the solenoid. It didn't matter whether the wires to engage (small terminals) the solenoid were physically connected.

 

[dlichterman]

I was talking about the main poles (large terminals) on the solenoid. It didn't matter whether the wires to engage (small terminals) the solenoid were physically connected.

Sounds like it may be defective then. Without power to the smaller terminals it should be open. Once power is applied....then it will close and join. Do you hear it click?

 

[dwh]

Btw, sounds like "dwh" envisioned you had both batteries connected to the solenoid while I dont think you initially said that...

Yes, that is what he said:

Before I connected the positive cable from the solenoid to the truck battery I checked the continuity (ignition off) across the solenoid and it was open (as it should be). When I connect to the truck battery I get continuity across the solenoid (ignition off).

The blue line is continuity. Put the tester across the terminals of the solenoid - it won't matter if it is engaged or not - it will read continuity:

 

[ludeykrus]

Question for the guys smarter than me...

I'm looking at installing the basic setup from earlier in this thread. Looking to have the starting battery in the engine compartment, two marine batteries in the bed tied to a solar panel/controller and an inverter. I have 00 wire ran from the starting battery to the inverter currently.

I have a receiver-mount 12k winch, and would like to be able to plug it into power at the rear of the truck (no dedicated hardwiring currently). Would I be overwhelming anything by connecting the winch at the rear house batteries with heavy wire and an inline 150 amp circuit breaker right off the starting battery? I'm not sure the winch would pull over 150 amps from the front of the truck with the two batteries inline along the way...

 

[dlichterman]

Question for the guys smarter than me...

I'm looking at installing the basic setup from earlier in this thread. Looking to have the starting battery in the engine compartment, two marine batteries in the bed tied to a solar panel/controller and an inverter. I have 00 wire ran from the starting battery to the inverter currently.

I have a receiver-mount 12k winch, and would like to be able to plug it into power at the rear of the truck (no dedicated hardwiring currently). Would I be overwhelming anything by connecting the winch at the rear house batteries with heavy wire and an inline 150 amp circuit breaker right off the starting battery?

Someone else might have a better answer, but with the amount of amps you are pulling you want to keep the runs as short as possible.

 

[ludeykrus]

^ True, I don't think the 2/0 cable would be a restriction from front to back on its own for the winch, but I'm thinking the circuit breaker may trip under a hard winch. Not sure if the two batteries inline would help by acting like a capacitor...

 

[dlichterman]

^ True, I don't think the 2/0 cable would be a restriction from front to back on its own for the winch, but I'm thinking the circuit breaker may trip under a hard winch. Not sure if the two batteries inline would help by acting like a capacitor...

I tried googling 12k lb winches and it seems like they can draw up to 450 amps......which is kinda a lot.....

 

[dwh]

Question for the guys smarter than me...

I'm looking at installing the basic setup from earlier in this thread. Looking to have the starting battery in the engine compartment, two marine batteries in the bed tied to a solar panel/controller and an inverter. I have 00 wire ran from the starting battery to the inverter currently.

I have a receiver-mount 12k winch, and would like to be able to plug it into power at the rear of the truck (no dedicated hardwiring currently). Would I be overwhelming anything by connecting the winch at the rear house batteries with heavy wire and an inline 150 amp circuit breaker right off the starting battery? I'm not sure the winch would pull over 150 amps from the front of the truck with the two batteries inline along the way...

When the winch fires up, the voltage of the entire bus will drop. Some power will flow into the bus from the rear batteries, some from the front battery, some from the alternator.

The rear batteries are probably deep cycle, the front probably a cranking battery. The cranking battery will have a lower resistance and can supply more amps faster than the rear batteries. The alternator is even faster at dumping amps into the bus than the cranking battery.

As noted, a 12k winch can draw as much as 450a at FLR (full locked rotor). It depends on the motor and the gearing, and it's unlikely that you'll ever load it until it stalls. So that 450a number is probably not a big enough deal to really worry about.

A 50' or less loop of 2/0 welding cable can handle up to 500a at a duty cycle of 60% or less (and your winch might not be rated for a 60% duty cycle anyway), so no worries about the cable.

The 150a breaker will probably pop if you load that winch up pretty heavy (and it sure will before you hit FLR and it stalls) - but maybe not. If it does, go bigger.

What's the solenoid rated at?

 

[ludeykrus]

When the winch fires up, the voltage of the entire bus will drop. Some power will flow into the bus from the rear batteries, some from the front battery, some from the alternator.

The rear batteries are probably deep cycle, the front probably a cranking battery. The cranking battery will have a lower resistance and can supply more amps faster than the rear batteries. The alternator is even faster at dumping amps into the bus than the cranking battery.

As noted, a 12k winch can draw as much as 450a at FLR (full locked rotor). It depends on the motor and the gearing, and it's unlikely that you'll ever load it until it stalls. So that 450a number is probably not a big enough deal to really worry about.

A 50' or less loop of 2/0 welding cable can handle up to 500a at a duty cycle of 60% or less (and your winch might not be rated for a 60% duty cycle anyway), so no worries about the cable.

The 150a breaker will probably pop if you load that winch up pretty heavy (and it sure will before you hit FLR and it stalls) - but maybe not. If it does, go bigger.

What's the solenoid rated at?

I did some research and looks like I should be pulling around ~300 amps pulling 12k, which is ~1.5 times my expected truck weight. Guess I need to see if I can find a good yet reasonably priced ~250-300 amp circuit breaker. EDIT - looking around, looks like I may be better served splitting the wire end and running 2x 150 amp breakers. Having trouble finding something suitable at higher amperages.

Haven't purchased the solenoid yet; I believe I've found a 300 amp continuous duty solenoid that will work, though.

 

[4RunAmok]

For whatever it's worth, we install plenty of warn winches on emergency vehicles at work, and we don't put fuses or breakers on any of them. They're hooked directly to the battery, cables wrapped in loom, and zip tying them to make sure they are secure and run through a safe path. Warn's own instructions do not include breakers, solenoids or fuses.

 

[IdaSHO]

Thats because they spec and/or supply the correctly OVERSIZED wire based upon winch and wire length.

If it is sized to exceed the max amp draw for the winch, a fuse is not needed.

Many winches have overload protection/interupt as well these days, dont they?

 

[Cyberman]

All of the circuit protection is inside the control box in a winch.

 

[dwh]

EDIT - looking around, looks like I may be better served splitting the wire end and running 2x 150 amp breakers.

I wouldn't. If one has a higher resistance, the other will end up popping.

Just use ANL fuses. They're cheap and easy, and if you get a fuse holder with a high rating, you can change fuse sizes to whatever you end up needing.

http://www.wiringproducts.com/anl-fuses

 

[oscar the grouch]

question. how would i translate this to putting the second battery on the trailer?

I want to run a fridge off its own battery on the trailer but charge when the jeep is connected and running.