Research On Negative Terminal Protective Type Intelligent Electric Bicycle Lithium-ion Battery Protection System

Lithium-ion battery protection as the key component of the electric bicycles, which is the current focus in the electric bicycle research. Due to its features such as safety, cheapness, environmental protector and energy conservation, the electric bicycle is promoted energetically by the government. Energy source of electric bicycles is the lithium-ion battery packs, which is a clear energy, having a high energy density, long life cycle and no pollution characteristics. Just because of the above characters, the lithiumion batteries have been widely used in electric bicycles and electric vehicles. Due to the inconsistencies in the processes of the lithium-ion battery, when the lithium battery working in series, with the increase in frequency of charge and discharge, the voltage value of difference between the lithium-ion battery monomers will continue to be larger, which would cause the lithium-ion batteries overcharge and over-discharge phenomenon. Lithium-ion battery protector is mainly used to ensure that lithium-ion battery of safe, efficient, low-power operation during use. At present, the major challenges for the design of lithium-ion battery protector is the safety using of lithium batteries, the charging and discharging efficiency and high costs.Combined with the lithium-ion batteries balanced protection technology, this paper design a negative terminal protective type intelligent lithium-ion battery protection of the electric bicycle. The protector is mainly made up by two parts: the monomer battery equalization control unit, and the vehicle switch protector unit. The monomer battery equalization control unit consists of acquisition voltage of single cell module and battery balanced protector module; the vehicle switch protector unit consists of battery overcharge, over-discharge, over-current and over-temperature protector. Finally, in the MATLAB/Simulink model of battery the equalization method was verified, and the equalization method was applied the equalization method to the equalizer protecting of lithium-ion battery protector.The results of the experimental show the feasibility of the above-described design. Protector can play a greatly accurate protective effect in charging and discharging of the electric bicycle. When the voltage value of the cell reaches the overcharge threshold 4.2V in the charging, protector can turn on the overcharge protection; when the voltage value of the cell reaches the over-discharge threshold 2.5V, protector can turn on the overcharge protection. Finally, the feasibility of the equalization method was verified in the battery model and applied to the electric bicycle protector. The above research provides a theoretical basis and experimental platform for the future research.