Lithium battery with power-off protection function

The utility model provides a lithium battery with a power-off protection function, and an external battery does not need to be added to the lithium battery. The lithium battery comprises a battery pack and a battery management system connected to two ends of the battery pack through a DC-DC power supply module. The battery management system is connected with a discharging relay and a charging circuit breaker, a system switch and a starting switch are connected in series between the battery pack and the DC-DC power supply module, the starting switch is a non-self-locking switch, the battery management system is also connected with a low voltage power-off relay, and a normally open contact of the low voltage power-off relay is connected in parallel with the starting switch. In the lithium battery with the power-off protection function, when the electric quantity of the lithium battery is too low, an external load is cut off, in order to prevent over-discharge, of the lithium battery, caused by electricity consumption of the battery management system, the power supply of the battery management system is also cut off, if necessary. According to the utility model, an external lead acid battery used for supplying power to the lithium battery is not needed, and self over-discharge, of the battery pack, caused by electricity consumption of the battery management system can be effectively prevented.