Wiring problem

[RogerDat]

Originally Posted by Carol H

....Thomas you may be correct re the crux. All I know is on my trailer it takes a number of hours of driving just for the tow to fully recharge the trailer battery that isnt close to being discharged to 50% to start with & even though I am not running the fridge while driving.....

Unless you have pretty heavy wire between TV charging and trailer the voltage that the trailer battery is getting won't be high enough to push charge in very fast. Your doing very well if you have enough to ever reach 100% battery charge.

We did one time flatten an RV battery in good condition by running fridge, stereo (plus two power booster amps) and lights while doing a straight through run from Mi. to Colorado in a motor home. So I know it is possible to drain battery while hooked to running alternator as Carol suggests.

That was a short heavy wire run from 150 amp alternator to battery. Bigger wire and shorter run than typical for RV trailer. It took about 16 hrs and things started dying, thank goodness for battery isolator. Oh and other bank of RV batteries. Still not happy to get below that 50% charge on the one that was drained.

Between myself and the kids had three CDL's plus two that could handle a stick and air brakes, easiest long trip I ever made, except for the part where driver gets to pick the music. Knew more about what kids were listening to than I wanted by the time we arrived <_<

[Thomas G.]

Originally Posted by Carol H

Thomas you may be correct re the crux. All I know is on my trailer it takes a number of hours of driving just for the tow to fully recharge the trailer battery that isnt close to being discharged to 50% to start with & even though I am not running the fridge while driving. Both my car and trailer have batteries less than a year old so they are in good shape. If the car battery is more than 4 years old and has been allowed to fall below 50% a few times it isnt going to be holding a whole lot of charge for long (same as the trailers) perhaps just enough to turn the car over so I would think the car is going to be working on recharging its own battery, as well as the trailers if its down and the 12V fridge on top of it all .... just dont think it is likely to do that very fast or well - for sure a drive of just an hour or two isnt going to be much help.

Just call me Tom.



Roger explained it well with his analogy to pumping up a tire. It comes down to the voltage available at the trailer battery during charging. The voltage starts out at about 14.5 volts at the TV's alternator and is reduced by every millimeter of wire and connection. Add a load like a refrigerator and the voltage drop is even greater - in fact a guy named Ohm had a great theory about all this.

Unless and until you measure the voltage at your battery while charging, you really don't know what is going on. You may be trying to inflate a tire to 35 PSI with a 35.1 PSI hose. Thus the heavy gage wire requirement.

[mszabo]

First is the battery good or bad? Have you had it tested. Until you do that nothing else matters.
Battery ok, then how many amp draw on battery?
Is there a amp draw with tv unhooked and everything turned off?
Keep it simple

[RogerDat]

Originally Posted by mszabo

First is the battery good or bad? Have you had it tested. Until you do that nothing else matters.
Battery ok, then how many amp draw on battery?
Is there a amp draw with tv unhooked and everything turned off?
Keep it simple

Works if you have a meter and can use it to measure amp draw. The process of elimination steps or suggestions on what might be the cause are a "no meter" approach that depend on nothing but logic steps or things anyone can check that can take you pretty close to the source.

Would be worth a stop at one of those auto parts stores that test batteries for free but clearly something was hammering the TV battery, only a question of where located. Trailer or TV, if trailer then what appliance.

Think it's been tracked down to fridge on 12 volt, with plans to have TV battery tested to make sure being run down has not hurt it too much.

[Thomas G.]

Originally Posted by RogerDat

...........Think it's been tracked down to fridge on 12 volt, with plans to have TV battery tested to make sure being run down has not hurt it too much.

Yes, I think the OP nailed it in post #15. You need a relay between the TV and the trailer battery and a heavy gauge wire, especially if you want to run an absorption type refrigerator while towing.

And even with that, you need to disconnect the fridge from the trailer battery when the TV is not running.

[Darwin Maring]

Key to a cold fridge when traveling: Run the Fridge on shore power 2 days B 4 departure and Freeze some bottled drinking water in the home fridge and move them to the camper fridge just prior to departure. You will be putting frozen water bottles in a cold fridge and that will get you through the first day and hopefully shore power during the camping night will help extend the frozen water bottles for another day.