The world champion in terms of power density, with 1.5Kg for a 37v / 8 ah pack ! Before thinking "too expensive", think that his life cycle is 800 to 1500. Kokam, leader on R/C Li-Po battery market, is really the battery magician ! Same as Li-Ion Battery, an electronic protection circuit (BMS) manage charge and discharge of each individual element to avoid damage . A really high-tech Jewel now available... 35-50Km range with 350W Phantom motor, 60km with street legal mode ! 1,55 Kg sizing : 55x110x210mm Only for 250W with the energy drink.