I had Les install the BEP system a couple months ago. I had two group 24 batteries to start with. I added another group 24 for a house battery. I started with that and the BEP system. Then, after having some problems and talking to Les, I took out the two group 24's and replaced them with 2 U1 batteries. Much smaller for starting. After starting they charge back to full within 30 seconds or so. Then after they are up to 13.7 and 45 seconds goes by everything goes over to the house battery. Either one, or both engines (honda 35's). Initially they weren't making the switch, but we discovered the relays have a very small ground wire tucked up under them and it has to be run to the common negative buss. I did that friday, and saturday gave the system a try. Worked like a charm. I ran the furnace, all the instruments, sirrius radio, and the radar, and returned home after a day and a night on the hook, with a fully charged house battery. Pretty foolproof system. I may add another house battery if I add refrigeration, and use a manual switch. Haven't decided yet if it is necessary.