goto lipo mode (if you are using lipo batteries) pess right button
press < / > arrow keys to change to larger than 4200, press right button again
press < / > keys to choose 2s / 3S then press right button again
press right button and hold on until it starts to check your battery
after checking, it battery is ok, it will start to charge until the voltage approach 8.4V (for 2S)