DYU Electric Folding Bike Spare Battery D3F/D3+/D2/D2F ??BMS Protection Board?Built-in battery holder, have better shockproof effect. Prevent over charge, over discharge, over current and short circuit and ensure the long life expectancy.??Design?Easy to take and remove. The LED battery level light can inform you of charging in time. ??High Quality Lithium ion Battery?This battery's made from lithium ion that keeps a charge and keeps its shelf life longer than lithium iron batteries that tend to die out quickly. The outermost PVC material prevents rain from damaging the battery. Li-ion battery still has a capacity of more than 80% after 1000 cycles.