Trailer battery charge AWG wire size>

[genestoy]

Does anyone with a 2021/2022/2023 Yukon or Tahoe know what AWG wire size goes from the underhood fuse block to the trailer hitch 7-pin plug for the trailer battery charge?
Thanks

 

[jforb]

hard to tell looking at the wires, without taking stuff apart, but perhaps the metric equivalent of #12 or #14?

The fuse for Trailer Battery is #84 under the hood, it's a 30 amp fuse....

 

[genestoy]

Yes, I knew the fuse was a 30 amp so I am "guessing" it should be a 10awg wire because 12awg is only good for 20 amps and 10awg is good for 30 amps. I hope GM is not installing a 30 amp fuse for anything smaller than 10awg?
Thanks

 

[jforb]

Wire ampacity is not quite as strict as you might think....it depends on the application, and lots of other things.

One of the things I do in my spare time is mentor a high school robotics team. The competition we enter our robots in has a thick rulebook, and the specified minimum wire size for a 30 amp circuit in that application is #14 wire. And they don't catch on fire.

That said, you should use #10 wire in the trailer....

 

[genestoy]

A lot of the amperage capacity also depends on the length of the wire involved also which I am sure is much longer in a vehicle than a robot?

 

[jforb]

Wire length affects voltage drop.

The operating temperature of the wire is related to how much current it carries. The insulation of the wire has to be able to withstand the temperature increase due to higher current. So the routing of the wire, and how many wires are packed in the same space, etc has more to do with it than length.

If you don't trust automotive engineers to size wires properly, then you probably should get a horse....

 

[genestoy]

So, if anybody knows the actual wire size that would be very helpful. I have searched online for wire harness diagrams etc trying to find the AWG size to no avail and I know GM customer service is clueless about these types of questions so please chime in if you know.
Thanks

 

[wjburken]

For a 12V system I believe they should be 8AWG wires for a 30A load rated circuit. This is based on total voltage drop over the length of the wire.

This is based on my experience having designed truck equipment in the past and resources like the one linked below.

12 Volt - Wire Gauge vs. Amps

Maximum current (amps) in a 12V electrical circuit vs. size (AWG) and length of wire.

www.engineeringtoolbox.com

 

[jforb]

The wiring diagram in the factory service manual should list the wire size. Let me know when you find the manual, please. I've been looking for a while, no luck.

It's definitely not #8.

You could pull the connector out of the truck, disassemble it, and measure the wire, then you'd know for sure. But unless you plan to replace it with a larger wire, which would be rather tricky to do safely, I really don't see how it makes any difference?

 

[WalleyeMikeIII]

Curious why you want to know?

Not being a jerk here. But if you are planning on using the 12V line in the trailer connection, you already know the circuit has a 30A fuse in it, so anything you connect should have wire sized for 30A min.

 

[genestoy]

Many of us that tow travel trailers with a LifePo4 lithium battery have installed a DC-DC charger in the trailer to "up" the charge voltage to the battery. Some have had to replace the wiring from the tow vehicle battery to the DC-DC charger to keep the voltage loss to the charger to a minimum. I do not want to do that to my 2022 and mine appears to be working fine just idling in the driveway but have not actually towed any distance/hours with the charger yet so just thought I would ask here to see if anybody knew what the AWG of the wire actually was. Some folks I know have went to 10 AWG and others with larger chargers have went to 8 AWG in their tow vehicles, but none of those are these newer generation tow vehicles.

 

[tungsten]

On your truck trailer plug it should be the pin at 1 o'clock,look at the back.

 

[tungsten]

I understood the trailer charger only works when plugged in to 110v?
Driving its the vehicle alternator doing the charging?
Ive always run my genset with a 30a charger directly to the batts once parked.

 

[wjburken]

Whether the vehicle is new or old, 30A is 30A. Others may have run 10GA wire and have been fine because they never actually pulled the full 30A, but that doesn’t make it right. The fuse is there to protect the down stream circuit so any wire that is installed down stream of a 30A fuse needs to be rated to handle 30A without over heating due to excessive load or damaging the downstream device due to excessive voltage drop. I guess I don’t see why running 8GA vs 10GA wire is such a big obstacle. Don’t cut corners on something like this.

 

[jforb]

My point is that not all wire of the same gauge, under all conditions, has the same rated ampacity. There is more to it that simply wire size. And GM knows this and sizes all the wires in their vehicles accordingly.

If your trailer battery charging system can't tolerate the voltage drop of the smaller wire, then yes, you might need to upgrade the wire. Just be careful, GM takes a lot of effort to make the wires safe, and it's difficult to add wiring and make it as safe as the original harness.

 

[WalleyeMikeIII]

But, he might be on to something if he needs to draw near the max current and maintain a certain voltage at the charger. Minimizing the IR loss in the wire would be helpful in that case, and lean toward larger vs smaller wire.

Many fishermen see this issue with the newer large display fish finders in recreational boats. Keeping the voltage above the min needed to keep them running is aided by larger wire from the battery to the graph.

 

[Steebu]

If you don't trust automotive engineers to size wires properly, then you probably should get a horse....

I trust the automotive engineer - I don’t trust the beancounter who screams, “Mary! Mary! We can make an extra $2500 per vehicle if we use 40 guage wire! Nobody’s gonna notice or care!”

 

[Fless]

Not sure if this is consistent or not, but FWIW, the NBS trailer aux and electric brake wires are 12 gauge, each protected by a 30A J-case fuse. You might be able to find yours in the appropriate upfitter's guide.

 

[genestoy]

Just answered my own question, crawled under the back of my Yukon and luckily the factory leaves about 2 inches of the trailer wiring exposed before going into the 7-pin plug. The charge wire is 12 AWG which seems to be adequate for my installation as my DC-DC charger only puts out 18 amps to the battery.
Thanks for the help

 

[jforb]

Thanks for the update. My Tahoe does not have that much exposed wire, so I couldn't get a definite answer.

But I'm curious how you decided it's 12 AWG, since GM has been using metric wire sizes for decades....????