Hello, I am trying to use a DC voltage sensing relay to control a generator in order to charge my batteries when they get low on charge. I have two 12 volt batteries in parallel connected to an UPS Inverter/Battery Charger. This charger is powered by the generator. I want to connect (in parallel) a VRDC to the batteries to sense when they are discharged to a specific voltage level, in turn, starting the generator and begininng to charge the batteries. My question lies in turning the generator off. The VRDC has a cut out that can be set which would disable the generator at a specific voltage sensed across the batteries. I want this to be when the batteries are fully charged. But the problem with this is that chargers begin by bulk charging at say 14.4 volts and once they equalize, drop the voltage to like 13.4 volts to float the battery. A fully charged 12 volt battery should read about 12.7 volts. How do I set the VRDC to accept the higher voltage from the charger but somehow know when the the battery is fully charged? How do regular chargers manage this? If I set my VRDC to turn the generator on at say 12.2V and then off at say 14.5V (to allow for sensing the charge voltage of 14.4V), when will the generator ever turn off?? I'm stumped, any help is appreciated. I've added an attachment of a quick diagram to visualize. Thanks!