In the EU we usually get long power cords with our chargers. So this is probably not very useful info for US members.
Because I still had a few of these 2 prong adapters I decided to take the power cord off and attach one of these adapters. This is great for in your camera bag. No annoying long power cords anymore!
The best way to charge the batteries is putting the charger upside down I think. This will lower the risk to drop the charger once its hanging off the adapter.
Love the outcome!