Chargeyour battery with the EfestSlim K1 Charger. The Efest Slim K1 Charger is a high quality with a cost-efficient and portable design. The Efest Slim K1 Charger is a single slot charger with Micro USB input and charges at 1A. The LED indicates when your battery is charging and when the battery is fully charged. The Efest Slim K1 Charger features reverse polarity, short circuit, overcharge protection and many more safety features. The Efest Slim K1 Charger can charge different types of 3.6V/3.7V lithium batteries commonly used in electronic cigarettes, flashlights, electric tools, and more.