Originally Posted by RichHog
So let me get this straight. The charger/12V system tries to charge the batteries while operating all turned-on device givng a full charge (with the system plugged in to shore power). But the system is overloaded due to the drain of the exterior lights + internal Halogen lights, + water heater / fridge etc. So it takes out extra juice from the two batteries or in my case 1.25 batteries and after a while depletes them. So the charger get's tired and the system goes to a minus (-) condition causing all systems to begin to crater, the power display to flash as it reboots and the fridge to shut down. Something like that? So partial solution is to throw out both batteries and get a new pair so that there will be more reserve juice when needed?
That is pretty much correct. When you are connected to shore power and everything is functioning normally, the batteries contribute nothing to the powering of the load. As far as the converter is concerned the batteries are an additional load. Depending on the design of the converter, one of two things will happen when the converter reaches its maximum output. Either it will shut off in one of several ways, or it will produced a reduced voltage. Either one of these will cause the batteries to provide some or all of the power to the loads. However until this point is reached the converter will see the batteries as just a big resistor. If one or both of the batteries are bad, they will present less resistance to the converter and therefore will draw more current and take a bigger share of the available power.
In my last TT, I placed a large marine battery selector in the circuit. It had 4 positions, OFF, 1, 2, and BOTH. When I plugged into AC I would leave the switch in the BOTH position for 24 hours to assure the batteries were fully charged, and then took them out of the circuit by switching to the OFF position. If the trailer was parked for an extended period, I would switch back to both for a day every couple weeks or so. I have not done that yet in my current trailer, but plan to soon.
The one thing to remember out of all this is that one bad battery left in the circuit will eventually cause the other battery to go bad also.
Hope this helps,
P.S. I am not saying that a bad battery is definitely causing this problem. There are too many variables. The whole setup needs to be thoroughly checked out with a multimeter before one can be sure.