While lithium batteries with BMS protection can safely undergo full discharge or charge temporarily, prolonged storage at 0% is dangerous because the BMS continues drawing a small standby current, which may eventually drain cells to 0V and cause permanent damage - occasional full discharges are acceptable but should be recharged within 24 hours.
When lithium batteries are fully discharged, the chemical reactions inside the battery can change, directly affecting its capacity. For example, if a 21700 battery is over-discharged, its usable energy will be significantly reduced, leading to shorter usage time, and it may not be able to fully recharge to its original capacity.
Why do lithium ion batteries avoid full discharge?
The underlying reasons for avoiding full discharge include battery chemistry and cell structure. Lithium-ion batteries contain multiple cells that rely on a stable range of voltage for optimal performance. When a cell discharges fully, it may enter a condition known as deep discharge.
No, discharging a lithium-ion battery fully does not present immediate risks to devices. However, it can lead to long-term damage to the battery itself, affecting its performance and lifespan. When comparing fully discharging a lithium-ion battery to partially discharging it, the key difference lies in battery health.
Fully discharging a lithium-ion battery can lead to a number of negative consequences. It impacts battery lifespan, performance, and safety. Decreased Battery Lifespan: Fully discharging a lithium-ion battery decreases its overall lifespan. Lithium-ion batteries typically last longer if they are kept within a certain charge range.
Deep discharge occurs when a lithium-ion battery is depleted to a very low voltage, often below its nominal operating range. For 18650 and 21700 battery packs, this typically means reducing the charge to around 2.5 volts or lower. Regularly subjecting batteries to deep discharge can lead to irreversible damage and diminished capacity.
If you want to avoid your lithium-ion batteries self-discharging when fully charged, then you should avoid fully charging them. If you charge your batteries up to only 90-95% of their capacity, then they won't self-discharge as much.