Primarily, the charging indicator on the charging cable must be observed! This indicator determines whether the battery pack is fully charged or not. The charging indicator lights up red during the charging process. If the lithium packs are fully charged, the charging process is automatically terminated and the charging indicator switches back to green or green - red flashing. Please note that the charging time may also depend on the USB source (e.g. USB port on notebook or powerbank). We recommend using USB power supplies with at least 1A output current in order to comply with the specified charging time.