Auxiliary Switches - Wire Ampacity Questions

[HooliganActual]

Then again, isn’t there a duplicate set of aux leads in the passenger footwell?

Yes, but those are for the Aux Switches. I’m not sure where you are heading with that question though.

I was remarking to the fact that the DC-DC Charger which will typically have BIG leads connected to it to/from main battery, to/from a house battery and/or to/from solar panels and moves a lot of current and this generates a lot of heat itself, shouldn’t be located in the engine compartment. Typical setups of that unit have nothing to do with the Aux Switches.

maybe I’ve misunderstood what you are driving at…

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[TheGerman]

I have the factory installed Aux switch group, ran a 10 gauge wire from the engine bay to the truck bed to have (2) 12V outlets on the bed. I usually have a Dometic PLB40 connected to the 12V and then a Dometic CFX3 45 connected to the PLB40. The PLB 4 max draw is 8 amp. The Aux switch is set to run of the battery when ignition is off, the Jeep is monitoring the voltage and is turning of the aux switch when it get too low, so it not draining the battery totally. Once the Jeeps turns off the 12v to the switch the PLB40 is taking over to provide power to the fridge.
I was also using a EcoFlow RIVER Max Plus (max draw 12A) in the same setup w/o issues.

 

[MrBones]

Has anyone done any real world testing at or near the maximum current ratings of their JT's factory installed auxiliary switch fuses/wires? If so did you experience any blown fuses, excessive voltage drop, or other issues?

I know that the aux circuits are specified and fused at 40A (switches 1 & 2) and 15A (switches 3 & 4). However, the provided wires for each circuit don't appear to be appropriately sized for continuous use at these currents. I'm guessing that they're maybe 12ga and 18ga, which means max wire ampacities of somewhere around 30A and 14A respectively.

The reason for my question is that I'm considering running wiring to the bed of my '23 Mojave to charge an EcoFlow River 2 Pro portable power station. To get maximum charge rates I'll be stepping up the voltage with a Victron Orion Tr 12-30 which has a max output of 30A, so there's potential for current draw of as much as ~35A from the aux circuit.

Of course I'll run sufficiently large (6ga) wires from under the hood to the bed to handle the current and keep voltage drop to <3%. The Orion will be used in DC-DC converter mode at 15V and I'll use the Engine Shutdown Protection function to ensure that I don't drain the starter battery when the JT's engine isn't running. I also have the option to use an aux switch to actuate a secondary high current relay with dedicated wiring from the battery to the truck bed, but that's added complexity I'd prefer not to have. I'll add that the EcoFlow's max (solar) charge current is spec'd at 220W so my actual current may never exceed 20A anyway.

Thanks in advance for any input on this.
-Mark

Looks like you're quoting ampacity for #12 AWG and #18 AWG from the National Electrical Code. The NEC does not apply to automotive fabrication. SAE would be your guide. I'm looking at a chart that says for 2% VD you can run #10 at 30 A for almost 8 feet. #8 can go to 12 feet.

 

[msiminoff]

Looks like you're quoting ampacity for #12 AWG and #18 AWG from the National Electrical Code. The NEC does not apply to automotive fabrication. SAE would be your guide. I'm looking at a chart that says for 2% VD you can run #10 at 30 A for almost 8 feet. #8 can go to 12 feet.

This is great feedback, thanks @MrBones!
Yep I was using an NEC ampacity chart for wires in conduit Now that you've reminded me to use the SAE chart I can see that I've got a couple more amps to play with... but the max (depending on insulation) for 12ga is still only 45A.
Anyway, I'm still in the same situation with voltage drop (my goal is to be <3%). So I'll be using a dedicated relay and 6ga wire for exactly 3%VD at 30 feet and 35A (my expected max), and also allows me to safely protect the circuit with a 60 or 80A mega fuse.
-Mark

 

[msiminoff]

The Aux switch is set to run of the battery when ignition is off, the Jeep is monitoring the voltage and is turning of the aux switch when it get too low, so it not draining the battery totally.

Interesting! I didn't see anything about this functionality in the owners manual...
At what voltage does the JT turn off power to the Aux circuit when the "Battery" setting in selected the UConnect control panel?

 

[TheGerman]

Interesting! I didn't see anything about this functionality in the owners manual...
At what voltage does the JT turn off power to the Aux circuit when the "Battery" setting in selected the UConnect control panel?

Not sure what the cut-off voltage is, but once it's reached it shows a message on the screen and the Aux is turned off. I was totally surprised the first time when it happened as I didn't found anything about in the manual neither.

But from a post on the Wrangler site: Generally it means your battery's voltage is below 12 volts. uConnect has a safeguard that cuts non-essential electronics when the power's low.

 

[ShadowsPapa]

Hello, OP Here...
Looks like the consensus is what I had expected; the provided wiring is too small for high current loads, best to use a secondary relay.
I had hoped that somebody would have done some testing on this by now, or at the very least could confirm the actual wire gauge. I guess I'll be the one to do that (current/voltage drop) test and I'll measure the wire diameter too. Will report the results here.

WRT the relay selection; There are plenty of 12V relays available, you just need to choose one that meets or exceeds you maximum current requirements (it goes without saying that you also need to use the appropriate fuse -preferably AT the battery- to protect your chosen wire gauge). This is the one that I will be using.

-Mark

The switches and associated wiring are likely intended for common Jeep accessories - lighting, that sort of thing. Not for high current use.
Also - the wiring provided is ok for the length it's likely running. So though the wires seem pretty small for the 15 and 40 amp fuse ratings - it's a short wire and they assume a short distance - again, counting on the most popular accessories, normally lighter draw lighting, maybe radios, whatever.

When I ran wires to the rear of my truck for the 12v outlets and so on, I figured on a lot less draw than 40 amps and used wiring a lot larger than what the aux switch pigtails are - due to length.
Note that all gauge charts also show distance or length of wire.

 

[ShadowsPapa]

Interesting! I didn't see anything about this functionality in the owners manual...
At what voltage does the JT turn off power to the Aux circuit when the "Battery" setting in selected the UConnect control panel?

It's a self-protection, you can't determine or set that.
Aux switches will be shut off if you go to your truck and the 12volt batteries are too low - doesn't matter if you have anything connected and turned on or not, doesn't matter how you have the switches set.
If you go out and find the switches don't work, it's meaning your batteries are awfully low - and you should not be running them that low.
If you want that feature - get a 12v controller that will shut down a load if the supply voltage drops below a point you set - you can't do that in the truck.

 

[Escape.idiocracy]

https://wiringproducts.com/pages/wire-amperage-capacity-chart

?

 

[ShadowsPapa]

https://wiringproducts.com/pages/wire-amperage-capacity-chart

?

That's one of 'em.
There are several and sometimes they don't fully line up.
Some of them use a 3% drop, some like that one a 2% drop.
3% drop on 13 volts drops down to 12.6
2% drop on 13 volts drops down to 12.74

 

[HooliganActual]

I have the factory installed Aux switch group, ran a 10 gauge wire from the engine bay to the truck bed to have (2) 12V outlets on the bed. I usually have a Dometic PLB40 connected to the 12V and then a Dometic CFX3 45 connected to the PLB40. The PLB 4 max draw is 8 amp. The Aux switch is set to run of the battery when ignition is off, the Jeep is monitoring the voltage and is turning of the aux switch when it get too low, so it not draining the battery totally. Once the Jeeps turns off the 12v to the switch the PLB40 is taking over to provide power to the fridge.
I was also using a EcoFlow RIVER Max Plus (max draw 12A) in the same setup w/o issues.

Man, it sure seems like you are rolling the dice there. I’m not trying to be negative but you are draining your starter battery down until a protective feature “saves” it from being drained too far. What happens when you are out camping off grid running that setup, on day 2 the Jeep protects itself and shuts off the Aux Switch, and then any other thing (parasitic Aux Battery, left on dome light, too many times opening the driver side door and the headlights coming on, ad infinitum) reduces the starter battery voltage just below the minimum needed to crank.

It seems like it would be safer to set the Aux Switch to IGN On and not risk activating a safety feature (safety features can fail too).

I only bring this up because a bad Aux Battery killed my Main on a long week off grid posted up in the same spot camping. Not a fun end to the trip.

 

[TheGerman]

I did that for a few trips, from weekends to 3 weeks roadtrip and it was fine. Usual MO is to run of the truck power system during driving time and stops, once on camp site I usually disconnect as we move the fridge. But I had it connected and running of the truck when leaving things pack for hotel stays, and the truck shuts off the AUX after ~6h. But of course I have a little backup starter kit for just in case.

 

[chorky]

Then again, isn’t there a duplicate set of aux leads in the passenger footwell?

or, just use the 15A lead to switch a solid state relay run to battery with heavier gauge wiring.

Under the hood there is output's for aux switches 1-4

Under the passenger footwell area there are outputs for the same aux switches 1-4 as well as a ground wire, an ignition on wire and an always hot wire. Fused at 10a I think for those last two.

Hello, OP Here...
Looks like the consensus is what I had expected; the provided wiring is too small for high current loads, best to use a secondary relay.
I had hoped that somebody would have done some testing on this by now, or at the very least could confirm the actual wire gauge. I guess I'll be the one to do that (current/voltage drop) test and I'll measure the wire diameter too. Will report the results here.

WRT the relay selection; There are plenty of 12V relays available, you just need to choose one that meets or exceeds you maximum current requirements (it goes without saying that you also need to use the appropriate fuse -preferably AT the battery- to protect your chosen wire gauge). This is the one that I will be using.

-Mark

I'm not so sure trusting a 11 dollar part is wise.... Just my .02. As for aux switches 1 and 2 - I am pretty sure they are 10 ga. Voltage drop is a whole deal of its own. It changes depending on how long a wire is. So hoping for a set value of the aux switches isn't viable, too many variables. For running wires to the bed, I would not use anything less than 4ga. And honestly, 2 ga is probably a better choice. I ran 4ga for the rear bed accessories to plan for future expansion and reduce voltage drop over distance - it's a long run. And ran 1/0 for the rear winch.

 

[msiminoff]

I wrapped up the installation this past weekend... very happy with the results. With this setup I'm able to charge my EcoFlow River 2 Pro at 188 Watts without the need to boost charge voltage.

I wound up using a 120A relay and 6ga wire from the battery to the bed. The wiring is protected by a 60A Midi fuse located next to the main battery. I also added a flyback diode to protect the Aux circuit relay and changed the (40A, F92) Micro2 fuse for Aux switch #2 to a 5A one since this circuit will never see more than 1 amp or so.

I needed to do a little bit of trimming to fit my connector panel into the opening in the bed, but I was able to use the stock mounting holes in case I ever choose to install the factory 115V inverter outlet or put the blank plate back in.

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