YKS 4-Slots Smart Battery Charger with Car Charger For 1-4pcs 17500/17650/18500/18650/18670 Li-ion battery Li-ion(lithium Ion)cylindrical rechargeable batteries charger for 1-4pcs 17500/17650/18500/18650/18670 Li-ion battery Full charge detection system:Automatically detect the peak voltage and minimal current of the battery by accurate method CC/CV charge method,charge batteries fully and quickly.And complete individual channels,prevent batteries charge eache other. Error detection:Automatically detect abnormal temperature raising, the short circuit battery, other type battery (alkaline,NI-Cd, Ni-MH) then indicate error by LED 5Hz flash mode.Reverse polarity protection, protects the batteries against incorrectly installed batteries, indicate turn off. Come With a US-plug switching adapter for indoor use,and a 12V car charger adapter for in car use