Due to the influence of production and work environment, inconsistency of battery cells can occur, resulting in differences in voltage, capacity, internal resistance, and other properties, causing variations in the effective capacity and charge-discharge amount of each individual battery cell during actual use. Therefore, in order to ensure the overall performance and prolong the service life of battery management system, it is necessary to carry out balance control of batteries to reduce variations among individual battery cells.
Balance management of the battery condition monitoring system helps to maintain battery capacity and control discharge depth. Without balance control of batteries, due to the protective function setting of the battery management system, some battery cells may not be fully charged when one battery cell is fully charged, or some battery cell with the minimum power may be cut off during discharge when other batteries have not reached the discharge cutoff limit.
Once the battery is overcharged or over-discharged, irreversible chemical reactions occur inside the battery, affecting the properties of the battery, and thus affecting the service life of the battery.
According to the circuit structure and control mode of balance management, the former can be divided into centralized balance and distributed balance, and the latter can be divided into active balance and passive balance.
Centralized balance refers to all battery cells in the battery group sharing one balancer for balance control, while distributed balance refers to one or several battery cells using a dedicated balancer. The centralized battery management system offers a faster balance speed and functions through simple and direct communication mechanisms, promoting efficiency and enhancing operational reliability.
However, the wiring arrangement between battery cells and balancer is complex and not suitable for battery systems with a large number of battery cells. The latter can solve the wiring problems of the former, but the cost is higher.
Active balance, also known as non-dissipative balance, is to transfer energy between battery cells. The energy in the battery cell with high energy is transferred to the cell with low energy to achieve energy balance.
Passive balance is a dissipative balance that uses parallel resistors to consume energy from the battery cell with high energy to achieve balance with other cells. Active balance has high efficiency and transfers energy instead of consuming it, but the complex structure brings higher costs.
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