7-Pin Amps to Trailer

[RoadTurtle]

I've seen all kinds of claims, 3-4a all the way up to 25a.

2022 F350D, towing a 5th wheel, solar input current was shut off, so the only source of energy was from 7 pin going into the battery. i intentionally ran the 5th wheel Lithium battery banks down pretty far. I have dual alternators, but don't recall the total alternator capacity.

While on the freeway, 68 mph, the 5th wheel battery bank was receiving 15.5a

 

[Lt.Dan]

The difference in claims can vary a LOT.

The number one reason I'm not a fan of charging through the 7 pin is most of the time the wire is not large enough to carry the amperage, so there is a ton of voltage sag from your alternator to the RV battery. Some trucks do better than others. I bet my old 96 F350 is in the 3-5amp range lol.

 

[RoadTurtle]

The difference in claims can vary a LOT.

The number one reason I'm not a fan of charging through the 7 pin is most of the time the wire is not large enough to carry the amperage, so there is a ton of voltage sag from your alternator to the RV battery. Some trucks do better than others. I bet my old 96 F350 is in the 3-5amp range lol.

It was an interesting experiment. I actually expected lower. My 5er wiring from 7-pin looks like a rats nest.

 

[HRTKD]

Was the LiFePO4 battery bank connected directly to the 7-pin circuit? Or, was there a DC-DC charger in the circuit?

Most Super Duty diesel trucks with dual alternators are going to have a maximum amp rating of around 397 amps. But that doesn't mean that many amps are available to the towing circuit which goes through a 30 amp relay from what I understand. 15 amps isn't much, but it isn't zero either. It would be interesting to see the voltage from the 7-pin circuit as observed on the trailer side as close to the battery bank as possible.

 

[RoadTurtle]

Was the LiFePO4 battery bank connected directly to the 7-pin circuit? Or, was there a DC-DC charger in the circuit?

Most Super Duty diesel trucks with dual alternators are going to have a maximum amp rating of around 397 amps. But that doesn't mean that many amps are available to the towing circuit which goes through a 30 amp relay from what I understand. 15 amps isn't much, but it isn't zero either. It would be interesting to see the voltage from the 7-pin circuit as observed on the trailer side as close to the battery bank as possible.

Only 7 pin.

Didn't measure the voltage, and the 7 pin runs through the original 5th wheel wiring which has proven itself to be suspect. Hoping to make that a project this summer to fix it. 7 pin on the truck is fused to 30a.

 

[Checkthisout]

Only 7 pin.

Didn't measure the voltage, and the 7 pin runs through the original 5th wheel wiring which has proven itself to be suspect. Hoping to make that a project this summer to fix it. 7 pin on the truck is fused to 30a.

Why wouldn't it get 15 amps?

If it shorts in the trailer, it will pop the 25-30 amp fuse on the truck right?

So why would it be inconceivable that it would get 15 amps or about 200 watts?

 

[RoadTurtle]

Why wouldn't it get 15 amps?

If it shorts in the trailer, it will pop the 25-30 amp fuse on the truck right?

So why would it be inconceivable that it would get 15 amps or about 200 watts?

I did get 15a in the trailer. Truck is fused to 30a... So theoretically, I would expect to see 25a. There's a rat nest between trailer 7 pin wires and trailer wires. I've seen enough wiring issues in the trailer to suspect another poor connection somewhere.