I have to
be careful using the outlet to charge the battery because the male
lighter plug would be hot on two exposed terminals if connected to the
charger first.

-jsw

Yeah, and I don't know what kind of lighter plugs you use, but capacity might also be an issue. Anyway, I maintain that ciggie plugs are just dumb. The only reason we have them is because the socket is already there, but it wasn't intended to supply juice to accessories, let alone accept it for charging.