Intai's intelligent chargers use the fast and safe charging technology for 18650 lithium battery and the finest materials that built for optimum performance, with built in safety features such as a reverse polarity alert, easy to read LED indicators, automatic short circuit / reverse polarity protection, backfeed protection CHARGING INDICATOR A yellow LED light indicates that the battery is being charged, flashing red LED light indicate that the battery is faulty or misconnected. AUTOMATIC SHUT OFF The automatic battery charger is designed to shut off once battery charging is complete to prevent overcharging. SAFETY CERTIFICATIONS: UL1310 Class 2 battery charger and Canadian Standard for Battery Charger 18650, CAN/CSA C22.2 No. 223(File No. E491233), TUV/EN60335-2-29 and RCM AS/NZS60335-2-29 Particular requirements for battery pack charger. RELIABILITY this high quality battery charger is built to ensure a MTBF better than 40000 hours at 35℃.