( The battery is rechargeable ) Use the micro USB charging cable to Connect the charging port of headphone and USB port which support 5Vpower (such as AC/DC USB adapter or PC USB port) Note:AC/DC adapter output must be 5V. Otherwise it may damage the headphones When charging, the red light is on. After fully charged, the blue light is on.lt takes about 2.5hours to charge the headphone fully. ‘Du DU’ Low battery alarm:When the headphone beeps and the the red light ashing .