Why lithium batteries must be equipped with BMS, while lead-acid batteries do not need to be equipped with BMS？
Lithium batteries need one more BMS battery management system to protect the cells than lead-acid batteries. Why?
The reason why lithium batteries (rechargeable) need protection is firstly related to their own material properties.
The material of the positive plate of the lead-acid battery cell is lead dioxide (PbO2); the material of the negative plate is spongy pure lead (Pb). Thicker materials include partitions and shells. It is made of materials with acid resistance, heat resistance, shock resistance, good insulation and certain mechanical properties. The electrolyte is made up of pure sulfuric acid and distilled water in a certain proportion.
Lithium-ion batteries mainly rely on the movement of lithium ions between the positive and negative electrodes. Lithium-ion batteries use an intercalated lithium compound as an electrode material. Commonly used as cathode materials for lithium-ion batteries are: lithium cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium nickelate (LiNiO2) and lithium iron phosphate (LiFePO4), which are actually used as the negative electrode of lithium-ion batteries The materials are generally carbon materials, such as graphite, soft carbon (such as coke, etc.), hard carbon, etc.
In terms of materials, the lithium of a lithium battery is more active than the lead of a lead-acid battery. The negative electrode material of a lithium battery is combustible. If it is to achieve the same safety as a lead-acid battery, the lithium battery cell needs a separator, a casing, etc. The material is made stronger and thicker, so that the lithium battery will be heavier and larger than the lead-acid battery. Obviously, this kind of thing is not allowed to happen.
Secondly, although lithium batteries have more advantages than other types of batteries, they are also limited by factors such as cell materials and current manufacturing processes, resulting in differences in internal resistance, capacity, and voltage between single-cell lithium batteries. Therefore, in practical applications, the individual cells in the battery pack are prone to uneven heat dissipation or excessive charging and discharging. Over time, these batteries in poor working conditions are likely to be damaged in advance, and the overall life of the battery pack is greatly shortened.
Finally, if the lithium-ion battery is in a severely overcharged state, there is still a danger of explosion, which will cause damage to the battery pack and threaten the personal safety of the user.
Therefore, lithium batteries must be equipped with a set of targeted battery management systems to effectively monitor, protect, energy balance and fault alarms for the battery pack, thereby improving the work efficiency, service life and safety of the entire power battery pack. .