AAA NiCd, NiMh battery. Maximize battery life that It can be used to manage the discharge of AAA single cells for MINI-Z Race Each cell is auto cut off and checked with LED lamp. It can be used without other power. Screw type battery terminal is comfortable to fix battery. Aluminum body is heat resistant. Specifications Dimension: 54 x 70 x 25.8mm Weight: 88g Cell No.: 1 - 4 LED: 4 Discharge Rate: 500mAh Cut Off voltage: 0.9V Source (MuchMore Racing): http://muchmoreracing.net/product_view.php?pidx=1382