Have your mechanic wire up a cig lighter plug that is hot even though
the master is off. Comes in handy for charging various stuff when
airplane camping. You can also charge the airplane battery by putting a
small solar panel on the top of the panel and plugging it into the cig
lighter.

rowntree wrote:

Due to a prolonged period of non use the 24V battery went flat on my
C172N. Is there any way a charger can be connected through the
external power point rather than the hassle of removing cowls to
connect battery charger alligator clips. It could be handy to connect
a trickle charger ocassionaly during long periods of non use? Arthur