I doubt the wall charger will do any damage to the battery since it charges at a pretty low rate. I'd be more concerned about safety. I generally charge my glow plug igniters with a wall charger overnight before I fly. One evening I walked out in the garage and immediately notice the burnt electrical smell. The wiring and charger had melted down and getting very hot. Luckily it didn't start to flame and burn down my house. After that I just don't care to charge any kind of battery unattended regardless of the battery chemistry or charger type.