We offer Li-Ion battery packs which are well engineered and protected with BMS (Battery Management System) for longest possible life. The cells used in our battery packs are A-grade LG, Samsung or Panasonic branded cells which have strict quality control and maintain their quality and performance for long. The technology and quality of cells are similar to what Tesla is using in their cars. There is a calendar life as well as cyclic life on the battery cells which is about 6 years and 800 full charge/discharge cycles. If using daily, you can expect about 20000-30000Km before the battery capacity shrinks to less than 50% which we consider as dead.