If the stock cradle doesn't work for some reason, your best option is the nyko power pak+ & charge dock
You can pick one up from Amazon for $7 - linky
It increases the system's battery life, but more importantly has three contacts on the bottom of the battery. When placed in the included charging dock, it will charge the battery directly (you won't get an orange light on your 3ds, as the 3ds is unaware of the charge, but it is actually charging.
Darnit, stupid me! I swear I read that differently the first time.did you even read his post?