When the battery runs low, the Red LED will flash every 2 seconds.
Recharge the CK210 by plugging it into a USB car charger that supports 5V/500mA-1A (not supplied) or PC USB port using the supplied charging cable.
It normally takes 1.5 hrs to fully charge the battery. The LED will indicate red when charging and turn off when charging is completed. It can work for up to 8 hours after full charged.