Battery charging via truck

[Tom48]

Originally Posted by CHICKDOE

I wanted to check out if there was more voltage in tow mode or with the lights on. I have a 2015 dodge ram 3500 with the cummins diesel and the heavy duty alternator. I got the same voltage measures (13.87 volts) at the 7 pin receptacle with nothing on, with tow mode on, with lights on, with tow mode and lights on.

Seems like it does not matter in a healthy system. But 13.8 v is not putting much more than a trickle charge in the RV battery. The concern to turn the headlights is to draw on the vehicle battery so the Alternator steps up. I will go up to about 14.7 if there is a demand and that thin wire all the way back to the trailer is not usually enough load to snap the alternator up to high output.

[Witch Doctor]

I have never heard that running in Tow Haul would increase your voltage from your alternator before. I heard of people leaving there lights on to keep the voltage up and not letting the alternator drop out, but I not even sure about that. I'm no mechanic for sure but the problem to me is that the wiring harness is not big enough to carry enough amps back to the TT batteries. You can measure the voltage but you still are not going to get enough amps through it to really give you more then a trickle charge. Am I wrong with that thinking. The pig tail wire is 10ga. I just changed one so I know that for a fact, 10 ga wire could carry 30 amps, but there is no way possible for you to get that kinda of amps to charge a battery from your TV. I have never tried to charge my batteries with my TV. I just always start out full charge. When I get to a CG and plug in the first thing my convertor go's to 14.4 volts for at least 4 hrs. So it is really not even keeping up with a full battery during travel. Is my thinking correct?....

[KyDan]

Originally Posted by Witch Doctor

....When I get to a CG and plug in the first thing my convertor go's to 14.4 volts for at least 4 hrs. So it is really not even keeping up with a full battery during travel. Is my thinking correct?....

I wonder if you are leaving home with a completely full charge? I agree with
the majority who say the voltage does not get all the way to the trailer battery high enough to give a good charge. I've demonstrated this myself.
Example- we boon docked in cold weather and left the CG with pretty low
trailer batteries. Drove 2 hours home. At home it was nearly dark so we
turned on lights in the trailer while we unloaded a few things. Lights went dim in just a few minutes demonstrating I had gotten pretty much zero charge while driving home.
BUT- I keep my trailer at home and keep a battery tender attached.
When we leave it's with a FULL charge. Typically when we arrive at a CG
and plug in my converter might surge for 5 minutes or so but then it's back
to maintenance charge.
If yours is running full bore for hours I gotta wonder if you left home with
a full charge.
My 3¢
Happy Trails!