Efest is a battery producer founded in 2009. Batteries are a vital part of your vape, they power the entire thing and you need to make sure they’re in good condition because if they aren’t you can damage your vape and yourself. Efest are a very reliable battery manufacturer their batteries range from the standard 18650 to the massive 26650, they also make external chargers for their batteries ranging from the single slot C1 to the quadruple slot Q4.