After the battery has been fully discharged and voltage lowers to the designated value, if we continue to discharge the battery, the battery will be over discharged. We usually set the cut-off voltage according to the discharging current. We often set cut-off voltage as 3.0V (Lipo cell) for battery with 0.2C-1C (normally) discharge current. Over discharging batteries, especially with large current, can bring disastrous results; over discharging batteries once and again will cause even worse result. Generally speaking, over discharging will cause battery’s internal pressure to rise, damage activity of positive electrode and negative electrode substance, decreasing battery’s capacity.