Charging The Batteries From The TV While Running The Refrigerator On Battery

[Philip]

Hello Folks,

After an extended three month trip out west last spring/summer the only disturbing problem turned out to be that the batteries discharged while towing with the refrigerator running on batteries. Yes I know many campers run the refrigerator on propane while towing but I am one who is not comfortable operating that way. First, the waste heat when running on propane is more than on electric and I worry about venting this heat with the shell covering the vent. Second, I prefer to have the propane off when towing - call me a bit of a safety freak!

Since we most often prefer to camp in state/national forest or national park campgrounds which generally do not have electric, it is most important to have the batteries charged when we set up. We prefer these campgrounds since they are generally more beautiful and less congested/crowded.

After quite a bit of investigating I finally found a web site where a fellow described how he solved this TV charging problem. This solution was also confirmed in a good book titled "Wiring for 12 Volts" by the guru of 12 volt systems, in my opinion, David Smead. The solution is to increase the wire size considerably from the TV battery to the TM batteries. The reason the charging rate is so low with the factory plug connection is that the charging wire sizes are woefully small causing too much of a voltage drop from the TV battery to the TM batteries. Keep in mind that the only driving force to charge the TM batteries from the TV is the voltage difference from the TV to TM batteries - generally 2 volts or much less.

Before making any charging system changes, the TV charged the batteries on the order of 3 or 4 amps or much less. I have a Link Lite battery monitor to measure amps. With the refrigerator running the batteries went into discharge when connected to the TV.

After revamping the charging system the TV charges the TM batteries at anywhere from 50 to 25 amps depending on the charge state of the TM batteries. The TM batteries are always charged well with the refrigerator and refrigerator fan running on battery. Here is what I did. Run #2 gage wires from the positive and negative post on the TV battery back to a new two pole plug on the rear of the TV. Run #2 gage wires from the TM batteries to a two pole plug(which plugs into the new TV plug) on the TM. The plug should be a very high amp plug so any voltage drop over the plug is very small. I used welding cable for the wire as it is quite cheap and very flexable. Also be sure to put a fuse(I used a 100 amp fuse) in the line from the TV battery so the TV will be safe if you should get a short anywhere in the TV wireing.

That's it and it works great. I will also be able to charge the TM batteries from the TV when set up in a campground should I need to.

My TV is a 2005 Toyota 4Runner with a factory tow package. The alternator is 100 amp and still sees a light duty cycle.

I hope this helps others solve this problem.

Take care,

Phil Friess