Batteries & Charging
Lithium-ion battery
What is a Lithium-ion battery?
A rechargeable battery that stores energy by moving lithium ions between two electrodes. Almost every e-bike battery is a pack of lithium-ion cells.
A lithium-ion battery stores energy by moving lithium ions from one electrode to the other as it charges, and back again as it powers the motor. An e-bike battery is a pack of many lithium-ion cells wired together, with a battery management system and a sealed case. The US EPA’s lithium-ion battery report explains how the cells work in more detail.
Why e-bikes use them
Bosch says lithium-ion batteries combine high mileage, low self-discharge and long service life with low weight, and that they don’t suffer from a memory effect. That last point means partial charges are fine. You don’t need to run the battery flat before you charge it.
What they don’t like
Heat, freezing, and long spells completely full or empty. Bosch says high temperatures, or storing a battery at a high or low charge level, shorten its life. The exact storage charge and temperature range depend on the pack, so “lithium-ion” alone doesn’t tell you what to do. Bosch recommends 30 to 60% charge for storage, while Shimano says about 70% for its STEPS batteries. Our winter battery storage guide compares them.
Also known as: lithium-ion batteries, Li-ion battery
Related terms
- Battery management system The electronics inside a battery pack that watch its cells and cut charging or power when temperature, current or charge level go outside safe limits.
- State of charge How full a battery is right now, shown as a percentage or as bars on the display. It is an estimate made by the battery's electronics.
- Self-discharge The slow loss of charge inside a battery while it sits unused, caused by chemical reactions in the cells.
- State of health How much of its original capacity a battery has kept, usually given as a percentage of what it held when new.