Hooked up the chassis battery of my Winnebago View on Nov 15, with voltage reading of 13.0V. Pulled the master disconnect under the dash; had rain for a 4 days out of 7 in the past week; Picked up the RV yesterday, Dec 9, 2019 and the chassis battery read 13.2 V. The house battery, also in disconnect mode, read 12.5 V, starting at 13.1 V as well. Now I need a Y connector and another set of clamps to connect those up, too, as this little gem delivers enough milliamps. My calculation : 7.0 Watts / 21 Volts of output = 300 mA or thereabouts; so 0.3A X 5 hours/day of sunshine gives 1.5 Amp hours per day X 7 days/week = 10 Amp hours / week, approx. And the house batteries declined by 30 Amp hours in those 3 weeks, so I need a Y connector to hook those up too!