Constantly Blowing The Charging Fuse in the Truck

[wdk450]

Gang:
I REALLY think this is a problem a lot of towable RV owners have, based on postings on RV interest forums. Personally, I would like my trailer battery system to be able to 1) reliably keep the refrigerator logic board going while travelling; and 2) Arrive at my new campground site with a fully charged battery set. What I have been experiencing over the years is that the 20 amp fuse in my truck's electrical system for charging the trailer batteries continually blows without warning or indication. The fuse in the truck blows (I don't know when or why), and the trailer batteries stop charging without me knowing about it.

I think I have come up with a simple solution for this problem - adding a self-resetting DC circuit breaker in the truck charging current path. I wired mine in at the umbilical connect steel electrical box. I bought a 20 amp breaker as my truck fuse for charging is 20 amp.
I did a little fuse "uprating" with the truck fuse to the next bigger size, 25 amps. I want the self resetting breaker to trip (which will "untrip" if the overload condition is gone), NOT the truck fuse to blow again without me knowing. I am thinking that it is standard electrical practice to fuse (or have circuit breakers) on ANY electrical power source (like the charging current from the truck) entering a building or vehicle. So I am thinking that Heartland SHOULD be installing these self-resetting circuit breakers at the umbilical cable termination in the electrical box.

After wiring this in, the fuse did not blow immediately as it did before, and with the truck engine on, I could now measure the trailer's battery bank voltage rising (with the shorepower converter/charger turned OFF). We'll see how it does down the road. I am going to MAKE CERTAIN that I unplug the truck umbilical very early in the campground space setup, so I don't have the truck alternator and the shorepower powered converter/charger competing. Also I don't want to try to have the landing gear lift the trailer, or move the slides, or any other high DC current demands with the umbilical still plugged in to avoid current draw overloads from the truck.

Here is the self resetting 20 amp circuit breaker I bought at O'rielly's Auto Parts:

 

[jbeletti]

Keep us updated on your experience with this Bill.

Note too that the trucks being produced today, handle this aux power line differently than your truck might.

From what I've read:
- We get very little charge current from the truck
- There may be diode protection on the circuit to prevent current flow from the RV to the truck
- Current flow is only possible when the truck is on and then, possibly only when a trailer is plugged into it

 

[danemayer]

Bill,

I think on newer builds, from what I've seen there is a breaker on the RV side.

I expect that what you've done will likely keep the truck fuse intact, but I'd start thinking about possible causes - what's pulling more than 20 amps? Battery problem? Insulation rubbed off somewhere?

 

[wdk450]

Keep us updated on your experience with this Bill.

Note too that the trucks being produced today, handle this aux power line differently than your truck might.

From what I've read:
- We get very little charge current from the truck
- There may be diode protection on the circuit to prevent current flow from the RV to the truck
- Current flow is only possible when the truck is on and then, possibly only when a trailer is plugged into it

Jim:
Nice to hear from you today. Dodge fused this charging line at 20 amps, so currents up to that should be expected. I have tested my 04 RAM truck and the charging line is live all the time. I also have the service manual in .pdf and the wiring diagrams reflect this.
Anyways, this mod has been done, and seems to work, I'll let the gang know when my next trip is completed.

On another note, Jim, I am thinking that since my family healthcare commitments have lessened, and my financial situation is a lot better, I will be looking into getting to some Heartland Western US rallies again.

 

[jbeletti]

Jim:
Nice to hear from you today. Dodge fused this charging line at 20 amps, so currents up to that should be expected. I have tested my 04 RAM truck and the charging line is live all the time. I also have the service manual in .pdf and the wiring diagrams reflect this.
Anyways, this mod has been done, and seems to work, I'll let the gang know when my next trip is completed.

On another note, Jim, I am thinking that since my family healthcare commitments have lessened, and my financial situation is a lot better, I will be looking into getting to some Heartland Western US rallies again.

It's the newer trucks with even more computerization that seem to have the limitations I mentioned.

Great to connect with you by phone today. Travel safe and maybe see you somewhere out west in the next year.