Trailer battery charge AWG wire size>

[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....????