I installed a "Piper" shore power socket, and wired the matching plug to a set of jumper cables. Below you can see the Nuckolls article that describes how to wire the socket, which includes another continuous duty contactor and "crowbar" circuit. In addition to what Nuckolls described, in place of crowbar circuit that blows the fuse, I went with a smart voltage detection circuit, such as would be used in a modern control system. The gist of it is - flip a toggle switch and the voltage detector runs with a power drain of 3 milliamps - on par with a quartz watch. - The inserted plug connects to the socket, which has its voltage detected and compared against low (9v) and high (15.7v) thresholds. This is protection against a battery cart trying to send a GA-standard 24v. - If between the two values, the detector closes a (normally open) relay and power goes to the contactor. Power flows to the battery. - If and as socket voltage spikes, the relay opens, the contactor opens and the socket is disconnected from the battery. Any fingers inside the socket can get pinched, but not shocked. - As a final protection, when the toggle is "OFF", there is no power to the voltage sensing relay and it goes back to its normal open, which removes voltage from the battery contactor. I've found that sometimes I don't want to bother with the socket and I just use a batter charger or jumper cables. In that case, positive goes on the battery side of the contactor and ground clips to the socket cover. Seems to work quite well... If I were doing it again I would install the unit in the forward hatch - easier access, no need to get the cabin wet on a rainy day, and further from any prop.