backup battery charger from ifirobotics

on our backup batt. charger we got 12.0 volts output to our board and 8.9 volts to the backup battey. we want to know if that is correct or not if not then what is it? please respond.

If you are reading 8.9 volts without the backup battery connected, that is normal. You are reading open circuit voltage from the charger, i.e. no load. The backup battery needs to be connected whenever the charger is powered and connected to the RC.