Change the battery level of android emulator (AVD)

$ adb devices
List of devices attached 
emulator-5554 device

$ telnet localhost 5554
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Android Console: type 'help' for a list of commands
OK

help
Android console command help:

    help|h|?         print a list of commands
    event            simulate hardware events
    geo              Geo-location commands
    gsm              GSM related commands
    cdma             CDMA related commands
    kill             kill the emulator instance
    network          manage network settings
    power            power related commands
    quit|exit        quit control session
    redir            manage port redirections
    sms              SMS related commands
    avd              control virtual device execution
    window           manage emulator window
    qemu             QEMU-specific commands
    sensor           manage emulator sensors

try 'help <command>' for command-specific help
OK

power
allows to change battery and AC power status

available sub-commands:
    display          display battery and charger state
    ac               set AC charging state
    status           set battery status
    present          set battery present state
    health           set battery health state
    capacity         set battery capacity state

KO: missing sub-command

power capacity 77
OK