For Plan A, the little battery's charging current should have been pulled from the house banks series strings, and not a single battery in the string.
Well, the problem is that I got Rolls-Surrette T12-250's and those are six cell 12 volt batteries. My system is 24 volt and the genset battery is 12 volt. There's no place I could hook to in the bank that would not cause an imbalance.
I could have had the RD-1 turn on a little 120 volt battery maintainer that runs off the inverters for a couple hours a day. That would work fine. But at that point it was like, well ....... one of them little 3 or 4 watt solar panels makes more sense
In the winter I don't need the genset battery maintainer. But in the summer we get lots of solar and our loads are lower so the genset turns into yard art and it's not used. Things in the winter that take a lot of power, such as my wife's electric clothes dryer that will cause the gen to start in Peak Power Management Mode, don't even get used because the clothesline works in the summer without freezing the clothes into solid ice.
I put my digital ammeter on the genset to see what it draws. The idle power consumption of the electronics in it is 40 milliamps, which is about 1 amp-hour a day. In two weeks, if it doesn't run to recharge the battery, the battery is low enough that it won't start. That little VW solar panel, if it can replace 1 amp-hour per day, on average, will work perfect.
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Chris