Modern hybrids and full electrical vehicles (EVs) use a lithium-ion (Li-ion) battery for power. These batteries are known for providing the most energy per size and weight. While physical attributes like size and weight are important, the electrical characteristics are what determines the effectiveness of the battery.
Of serious importance is the fact that Li-ion batteries are sensitive and high maintenance. If not used or treated correctly, they can be dangerous as they catch fire and otherwise cause damage. That’s why Li-ion auto batteries are accompanied by a battery-management system (BMS) that monitors and controls battery usage. The BMS is a complex and expensive subsystem, but it’s a necessity in modern EVs and hybrids.