For technical reasons, there is a recommended order of plugging in your batteries when charging, as well as removing your battery from the charger.
Fast Charging:
When charging: Plug in the charger to the device first, then to the wall outlet.
When done charging: Unplug from the wall first then device.
Variable Charging:
When charging: Plug into the outlet first, let the voltage on the charger settle, plug into device.
*Fan will not turn on until plugged into the battery.
When done charging: Turn off charger. Unplug from the device first then the wall.