When we bought our RV new to us, they gave a solar charger and the cigarette plug was somehow rigged to allow power to go back into the chassis battery. When we had an electrical problem and took it to the Ford dealer, they removed all the wiring and fuses that were jumped together explaining that that was the cause. After that I haven't used the solar charger, but if this is a common practice and the cigarette lighter does successfully charge the battery then I would love to you. Sorry to piggyback on this question but I didn't realize this may be common practice and thought it was a one-off that the previous owner had done.
