Very interesting indeed, Thanks for that...
theoldwizard1 wrote:
First we need to establish a baseline.
Disconnect the 2 batteries on the trailer and fully charge them. Disconnect the charger and let them "rest" for at least 30 minutes.
What is the voltage on each battery ? If there is even a small difference in voltage on each battery, the lower voltage battery will drain the higher voltage one, even with no load. You can prove this with you ammeter !
Drain to what extent? AFAIK they attempt to match voltage right? If they are close like .1 volt off will they not just equal in voltage? Maybe a few amps from one to the other?
With the engine running, what is the voltage at the truck battery terminals ? This varies. First 45 second are 14.4, then the ECM takes over. Could be 14.4 14.7, 15, 15.2.. It depends. Now what is the voltage at the Anderson connector ? Its the same. There is no drop if any at all.
Now plug the vehicle and RV together and measure the voltage at the RV batteries with no load from the RV.This can be anything. If RV batts were floated at 13.2 and truck was just turned off and was 13.7, im not sure what I would read. Last measure the voltage from the vehicle batter positive terminal to the positive terminal on the RV batteries. If life was perfect, the voltage drop would be zero. Yes this test on wirelosses I have been meaning to do. I believe I have them to a minimum. I will check tomorrow just to see as I have never done it.
REMEMBER, CURRENT FLOWS FROM HIGH VOLTAGE TO LOW VOLTAGE.
What you really want is about 13.8v-14.0V AT THE RV BATTERY TERMINALS, but you have no way to control this ! The vehicle voltage regulator is "sensing" voltage far from those batteries. If you had an alternator with an externally adjustable regulator, you could crank it up to the desired voltage, but the battery in the vehicle would probably be seeing close to 15.0V and it will be boiled dry. On my truck because its ECM controlled I always see 14.4-15.5 volts.
You will never be able to "balance" two power sources that are separated by a cable that has more than ZERO ohms resistance and voltage is being sensed at only one location. These two power source need to be SEPARATED and some electronics employed at each end to properly regulate the voltage. They do make DC-DC converters that can do this, but a high current one would be VERY expensive.
Understood. There is a hall effect sensor on the neg starting batt of these truck. I assume to sense the current and increase or reduce accordingly.
Something worth trying. Wire an Anderson connector off of the feed to the inverter. When you want to use the truck as the primary power source, connect it up directly to that connector, bypassing the RV batteries. Assuming the inverter is also powering your RV converter/charger AND the converter/charger is still wired to the RV batteries, they will be properly recharged.
What I want to use the truck for is this..
1. Go to sleep with truck plugged in to camper with anderson connector,Hopefully add some AH's to the two 150's.
2. Maybe wake up to dead batts and inverter alarm going off. Either in morning or @ 3am!!!!LOL.
3. If alarm going off and I dont want to get up and go set generator up and solar didnt kick in yet, start truck with auto starter. Truck runs for 20 min
4. Instead of setting up gen, run truck about an hour untill solar kicks in.
Basically I fear a low voltage condition at 3 am when my c pap is running.. But this is my first year of c pap machine and really dont know what to expect as I have not camped with it yet off inverter.
And I only did this in an attempt to pull more amps if needed instead of the #10 wire through the 7 pin.
20 ft of #10 vs 11 ft of #6.
