Truck not delivering power to trailer

[DanandDaphne]

Originally Posted by Centex

Respectfully, that's a common but incorrect misconception.

The OPD (Overfill Prevention Device) built-in to modern tanks serves to prevent overfilling of the tank but does not restrict gas flow if a regulator failure or 'open line' occurs.

Common 'portable' LPG tanks of the type we use in the RV environment lack an integral flow restricting device because there are some legitimate applications outside of our RV / BBQ experience which require very high flow rates.

However, a valve inside the 'green nut' of the pigtail between the tank and the regulator does serve as a safety device to severely restrict (but not necessarily completely stop) gas flow in the case of a regulator failure or 'open line' occurrence. It is this 'excess flow prevention valve', integral to the pigtail, which can 'block flow' sometimes when the tank main valve is opened too quickly, a phenomenon some folks have experienced much to their bewilderment.

But that doesn't explain why my propane tank shut itself down when it was 3/4 full. I didn't tip the tank over drop it or anything. The tank was being use on my home grill. It wouldn't let any gas out whether on the grill or not until I took it in and had it filled even though it was mostly full. After filling it it worked normally again.

So what happened then if there's not a flow stopping device in the tank valve?

[Centex]

Originally Posted by DanandDaphne

But that doesn't explain why my propane tank shut itself down when it was 3/4 full.

I agree it does not, nor would a properly functioning flow restriction device explain your issue.

I have no idea if your grill hose has an excess flow prevention device like our RV pigtails have, but if so, you may have fallen victim to the 'too fast opening phenomenon'; or the regulator on your propane grill may have malfunctioned - I have no idea.

FYI, the usual solution to the 'too fast opening phenomenon' (causing the excess flow prevention device in the RV pigtail to slam closed) is to remove pressure from both sides of the pigtail and let it sit for a period of time so the device can 'reset'. Perhaps that occurred while you were getting the tank filled?

[C&G in FL]

Originally Posted by DanandDaphne

But that doesn't explain why my propane tank shut itself down when it was 3/4 full. I didn't tip the tank over drop it or anything. The tank was being use on my home grill. It wouldn't let any gas out whether on the grill or not until I took it in and had it filled even though it was mostly full. After filling it it worked normally again.

So what happened then if there's not a flow stopping device in the tank valve?

This may be counter-intuitive, but if it happens again, hold the tank 12 to 18 inches above a solid surface such as asphalt or concrete and drop it straight down. Then see if it flows properly.

[DanandDaphne]

Originally Posted by Centex

I agree it does not, nor would a properly functioning flow restriction device explain your issue.

I have no idea if your grill hose has an excess flow prevention device like our RV pigtails have, but if so, you may have fallen victim to the 'too fast opening phenomenon'; or the regulator on your propane grill may have malfunctioned - I have no idea.

FYI, the usual solution to the 'too fast opening phenomenon' (causing the excess flow prevention device in the RV pigtail to slam closed) is to remove pressure from both sides of the pigtail and let it sit for a period of time so the device can 'reset'. Perhaps that occurred while you were getting the tank filled?

No, it wasn't the grill the tank itself completely shut down I tried using the propane tank on several different things, weed burner, and propane stove, nothing, no gas. I also tried just cracking the valve, same thing.

Originally Posted by C&G in FL

This may be counter-intuitive, but if it happens again, hold the tank 12 to 18 inches above a solid surface such as asphalt or concrete and drop it straight down. Then see if it flows properly.

I had read of this and so I tried that several times, all I did was bend the support ring a little bit (I straightened it back with vice grips).

[Mike G]

I have had trailers with fridges that wouldn't stay lit on the highway. But the Norcold in my E19 runs great on LP while traveling.

Power from the tow vehicle doesn't amount to a spit in a bucket for keeping the trailer battery charged. Maybe with some 4 gauge wire it would be of some modest help, but not with the usual light gauge wiring to the 7 pin. You'll get more significant assistance from solar panels; 300W in full sun might just about keep up. Don't feel too bad about not knowing; I was the same way a decade ago, and I shortened the lives of more than one battery trying to run the fridge on 12V DC all day. I was a slow learner!

[iamunique127]

Originally Posted by Mike G

....Don't feel too bad about not knowing; I was the same way a decade ago...

Ditto. I was under the impression the TV helped keep the batteries charged as well. I only learned otherwise on this forum.

[Chamberman]

I had an issue about 12 years ago with low flow from a propane tank. I typically have two tanks refilled at the same time for my backyard grill. One time when I returned home with the full tanks the 1st tank I connected would only barely flow any gas. Even when I could get the burners to light it would go out sporadically. I connected the 2nd tank and it worked no problem. I wasn't sure what was going on. I tried multiple things to get the bad tank working, removing the regulator and then putting it on a different appliance, etc. Nothing worked.

I finally took it back up to the store that refilled the tank and the owner took it out to the filling station but he didn't hook up the fill hose to it. He took a screwdriver and loosened the tank vent screw located on the neck of the tank valve, directly underneath the handle. He loosened it until it was blowing pretty good then tightened it back up. Then he handed me the tank and told me to take it home and try again. He said something about a vapor lock or air bubble blocking flow. Anyway, I took it home and low and behold that corrected the issue.

A few years ago I had the same extremely low flow issue happen again to me right after a tank fill. This time I took the tank out into the open area of my back yard away from the house and loosened that tank vent screw about 1 turn and let it blow for a few seconds and once again that corrected the low flow issue.

[Chamberman]

FYI, I previously linked to a youtube video about OPD & Excess flow valves being inside of the propane tank, but I do not believe that video was incorrect and I deleted the link. I believe that the excess flow valve is located inside of the regulator assy and not the tank.

I have however experienced low flow from a specific tank. Switched tanks to a different tank and the problem was not present.

I believe its quite possible that a piece of debris may actually be getting into the gas valve and blocking the flow.

[Tardigrade]

There is been so much great response to this thread. Unfortunately it's been raining since I posted it so I have not gone out and done any read troubleshooting. Don't think I'm ignoring you, I really appreciate the thoughts!

[Tardigrade]

Got some time to dig into it this weekend and TLDR I think everyone who said thicker gauge wire is correct. My next question is what gauge should I put in there? Do you think 10 will suffice?

The details. First off I want to say the Victron stuff is pretty cool. I got the app installed on my phone and connected to the DC/DC charger. The truck is definitely delivering power when the engine is running (not when it's off so I don't have to worry about battery drain).

I found that if I switch off the smart alternator and the minimum voltage shutdown it charges. I saw it delivering about 20 amps to the batteries. I reached under the truck to feel the wire about a minute into it charging and the wire was quite warm. Also, the input voltage dropped to about 9 volts pretty quickly. I re-enabled the settings since they are obviously there for a reason.

It seems pretty clear I need to change that wire. So now my main question is what gauge. From searching it seems like 12 would suffice but why not over build it a little while I'm working on it and go 10? Or is that just wasted money?

Thanks again to everyone for your input! I'll look into the propane next but honestly being able to use battery while on the move seems idea anyways.

[Rockhead]

I’d run a 10 gauge

[alanmalk]

Originally Posted by Tardigrade

...
It seems pretty clear I need to change that wire. So now my main question is what gauge. From searching it seems like 12 would suffice but why not over build it a little while I'm working on it and go 10? Or is that just wasted money?

Actually, there are reasons not to guess what gauge is correct. Tables are available on the internet for free and are highly recommended.

So, for a current of 25 Amps, and a voltage drop of 10%, and a round trip (alternator to load and back) of 40 feet: The tables recommend 10 gauge. Going smaller would be a waste of power, money and your effort. Going bigger is only going to impact your credit card.

[John in Santa Cruz]

10% of 14V is 1.4V making it 12.6V... I would use 8 ga, maybe even more. Both in the truck and from the trailer cable to your dc-dc

[brroberts]

I agree. While 10ga will carry the current, I would recommend using the 3% voltage drop tables for charging purposes.

[Mike G]

Go overkill, get the heaviest gauge wire you can afford.

[alanmalk]

Originally Posted by Mike G

Go overkill, get the heaviest gauge wire you can afford.

Don't forget, the OP has a DC/DC converter which will compensate somewhat for the 10% voltage drop. Yes, if I were to wire alternator directly to trailer battery, it would be a 70' round trip and 3% drop would be ideal to run the fridge and keep the batteries charged. That would require a small mortgage loan for the copper investment.