The DJI Phantom 2 manual says "It’s recommended to charge and discharge the battery thoroughly once every 20 charge/discharge cycles. Users should discharge the battery until there is less than 8% power left or until the battery can no longer be turned on. Users should then fully recharge the battery to maximum capacity. This power cycling procedure will ensure the battery is working at its optimal level." I usually stop flying when my battery is at 20% so I am wondering what is a good way to discharge the battery down to 8%?