Running the refrig on 12VDC while driving

We just got back from a 1,000 mile trip. On one day of the journey I measured the ability of my TV to charge the TM battery while in tow and with the fridge on 12 volt.

The only load on the battery when I measured the voltage was the propane detector, smoke detector and carbon monoxide detector. Fridge was still on propane, lights were out, radio had the fuse removed.

Left camp reading 12.1 volts. Arrived at destination and it measured 12.6 volts.

This was a 7 hour drive to go 197 miles. Did I mention the highway had a lot of turns?

Everything is stock from the factory. I would think anyone getting less charge than that clearly has a problem worthy of researching.

[Bill]

OK, it appears that about 1 in 5 of us have the same problem I do – if you run the refrig on 12VDC while driving for several hours, the TM battery is depleted when you arrive at your destination. My theory, often expressed, is insufficient wire size in the tow vehicle. (The wiring in the TM is heavy, as it should be.) In my case, the tow vehicle is my Ford Explorer, and I know that there is some lightweight wire in the harness from the battery to the Bargman.

To prove or disprove my theory, I ran a brand-new separate run of #10 wire, both power and ground, directly from the alternator of my Explorer to the battery in the TM. It works! Theory proved, at least in my situation. Without the new wire, the TM battery discharges slowly when the Bargman connector is connected, the Explorer engine running, and the TM refrig running on 12VDC. No other 12-volt loads. With the new wire, the TM battery is actually being charged while the refrig is running. This means that I could add (for example) a thermoelectric cooler or some other 12-volt load, and still arrive with the TM battery topped up.

As I mentioned in my post above, I was unwilling to break into the Bargman connector. To avoid this, I mounted a separate 6-pin connector on the rear bumper of the Explorer, and ran a separate cable under the TM to the battery. Photos are attached.

Old-timers on this board know that I enjoy most of my TM-related projects. This was not one of them. I had decided at the outset to do a very professional job, running the wire out of sight through the Explorer, behind various trim panels, and to carry it all the way through to the TM battery. Although the final result met my expectations, the work involved was not worth the effort and frustration. A much sloppier run of wire, tacked up to the undercarriage of the Explorer, and tapped into the Bargman at the rear bumper, would have been a lot easier and would still have solved the problem.

But now I know the answer.

Bill

[Speckul8r]

That's VERY cool, Bill. Glad the problem is solved!!

I am new to this forum, and maybe this has come up before, but here goes.

I was wondering if anyone had considered the Dodge, GM(s) trucks vs. Ford truck TV to the discharged TM battery poll. I was told that Dodge & GM(s) have a constant hot wire to the trailer, where the Ford wire is only hot while the engine is running. It would make since to me that if you stop somewhere with a Ford, that the fridge would only run off of the TM battery, drawing it down. In the Dodge or GMs, the fridge would pull off of both the TM battery and the TV battery, drawing a lot less on the TM battery. Just wondering. I am not sure about the setup on other vehicles.

[Bill]

You are correct about the Ford. They have a relay isolator built in. And you're right that it makes sense, and I love it. I can't speak for the other brands.

Bill

Quick question...does anyone else with a 2005 Tundra 4.7 v8 with trailer package have a problem with discharging the TM battery while towing with the refrig on 12 volt and the refrig fan running?

[commodor47]

Originally Posted by Tuscany Bandit

Quick question...does anyone else with a 2005 Tundra 4.7 v8 with trailer package have a problem with discharging the TM battery while towing with the refrig on 12 volt and the refrig fan running?

Check your Bargman connector on the TV. I had a similar problem while traveling west two years ago. Initially I thought the dead TM battery happened because we stopped too long for dinner. I left the refrigerator on DC with the outside fan running. About an hour later we stopped for the night and discovered the TM battery was all but drained. Usually our stops are shorter and we drive 3 to 4 hours before stopping for the night. The assumption is that the TM battery is charging while we drive and the refrigerator is working the way it should.

A while back Bill (Moderator) posted a picture of the Bargman connectors (TV and TM) and described how to check for a battery isolator on your TV. I discovered that there was no current at the battery charging terminal of the Bargman connector whether or not my TV engine was running. Crawling under the back bumper I noticed that there was no wire connected to the battery charging terminal of the connector. In essence I had been towing without the benefit of being able to charge the TM battery. So check your Bargman connector to make sure it does have a black wire connected to the charging terminal.

I couldn't understand why my TM battery had never drained down in all our previous travels. There is one possible explanation: the TM battery must be charging when the TV brakes are applied. The TM wiring diagram shows the blue (brake) wire running to the TM battery.

I had one turn signal not working in the middle of our third season. I checked ans swapped bulbs, cleaned bulb contacts.

The ultimate fix was I sprayed a liberal amount of WD40 on both the male and female ends of the plug, inserted it in and out several times and the problem went away.

Conclusion, a dirty contact blocked all voltage on one pin but not on any other.

[Joesjunk]

Originally Posted by Tuscany Bandit

Quick question...does anyone else with a 2005 Tundra 4.7 v8 with trailer package have a problem with discharging the TM battery while towing with the refrig on 12 volt and the refrig fan running?

I have a 2003 Tundra with a trailer package and my battery is low when running the refrig and fan on 12 volts during transit. I installed a new battery in the Trailmanor before I left on the 2005 trip.

Found this out on a cross country trip in 2005, while dry camping. Several times.

The brake controller was added after I purchased the truck and got the Trailmanor. I insisted that the battery connection to the Bargman connector be hot. Perhaps the installer screwed it up. I know that I should have done it myself. Well now it looks like I will have to do it myself. Maybe next month. It's 100 degrees here.

[Joesjunk]

The temperature dropped to the mid 80's and I was able to do some checking. The shop that installed my brake controller installed a #14 wire from the battery to the bargman connector. In the process he cut and spliced the existing #10, factory installed, power to the connector. This was connected directly to the battery, which gave no isolation between the TV and TM. They were always connected together.

I removed the installed wire and reconnected the original wire. I now have the original factory wiring. Looks like I have 12+ volts at the connector only when the igition switch is on. I also have the factory installed #10 wire, fused at 30 amps, to the bargman connector.

Just goes to show you, if you want the job done right, do it yourself.

Connecting the smaller wire to the larger wire is like connecting a smaller pipe to a larger one. No matter how much you try you can only get the current capability from the smaller of the two wires... Or the water carrying capability of the smaller pipes.

Have fun,