Towing Car Battery charging

[caki]

Hi:
I have an small RV (Clipper 17FQ) that I'm converting to a 24V Lithium battery with solar and shore power charging. I don't want to charge the battery with the towing vehicle power using the 7 wire connector. I tried to follow the wiring to see if I need to disconnect one of the wires from the trailer harness but I was not able to clearly understand the wiring. So my question is during a conversion like this (24 battery using a 24v to 12v converter), how to make sure that the vehicle power is not going to backfeed into the system? Should I add a diode on the 24v to 12v converter? Attached is a diagram of the my conversion. Thanks

 

[HRTKD]

Modern tow vehicles should have been setup to allow power to flow one way. I've left my truck connected to my RV trailer overnight without any issues.

Does your trailer have brakes? If so, you still need a 12v battery, or a 24v->12v converter to provide power to the breakaway system. The breakaway system on a dual axle trailer will pull about 12 amps. Half that for a single axle trailer, if it even has brakes.

 

[caki]

This is an used RV that had a 12v battery. It has electric breaks and the previous owner says that it can be charged with shore power (120v AC) or by 7 wire harness from a towing vehicle. I'm replacing the battery by a 24v to 12v converter (24v comes from my Lithium battery that is charged by solar or shore power). I'm also aware that I need the power to be present to power the breakaway breaking mechanism. But my question is basically I'm think that I'm connecting the 12v converter to the car battery and it seems to be me that I should have some mechanism to avoid that.

I followed the wiring, but I was not able to find where does the towing harness wire goes to charge the battery. It seems that it goes to the lights on the back of the RV.

 

[HRTKD]

Follow the 7-pin cable. On mine, it goes into a distribution panel (more of a box) towards the front of the trailer, on the underside. The trailer lights (running, brake, backup, etc) mate up with the 7-pin cable there. From the distribution panel you should be able to trace the 12v power circuit that goes into the trailer.

What made you decide to go with a 24v battery?

 

[caki]

I tried tracking for some hours this morning without success. The red cable seems to go directly to back of the trailer lights. I was hoping to have an workaround where I wouldn't have to trace the cable.
I decide on 24v because it seems to be a good compromise between 48v and 12v and most of the devices I need to use are 24v so it is a convenient voltage. I also got an used 24v battery 100ah lithium in a good deal, so that sealed the decision.

 

[caki]

I was able to find this diagram that seems to match the wire colors. I think I can use this to understand and snip the black wire.