Commonly used equalization charging techniques for the equalization principle of lithium-ion battery protection boards include constant shunt resistance equalization charging, on-off shunt resistance equalization charging, average battery voltage equalization charging, switched capacitor equalization charging, step-down converter equalization charging, inductance equalization charging, etc. When charging a group of lithium-ion batteries in series, ensure that each battery is charged in a balanced manner, otherwise the performance and life of the entire group of batteries will be affected during use.
It is necessary to adopt a balanced situation: in the case of battery production, the storage time is longer, because different various static power protection boards and various battery self-discharge rates form the entire bundle, and the battery voltage has a significant pressure difference, but With the same guarantee ability, the function of balancing the voltage of the battery pack under balanced conditions can achieve the effect of fully charged and fully discharged battery capacity, which makes the battery exert a huge impact.
When the battery pack has been produced and stored for a long time, due to the different static power consumption of each circuit of the protection board and the different self-discharge rate of each battery cell, the voltage of each string of the entire battery pack is inconsistent, resulting in a significant pressure difference , But under the condition of ensuring the same capacity, the equalization has the function of equalizing the voltage of the battery pack, so as to achieve the function of full charge and full discharge of the battery pack capacity, so that the battery pack can exert great effect.
The battery itself still has available capacity, but due to the imbalance between the batteries and the safety voltage limit set to protect the battery, the battery system cannot continue to perform its due performance. In addition, the service life of the battery in the vehicle is shorter than that of the vehicle itself. Even if the vehicle has not reached the end of life, the battery must be replaced in order to meet the power performance. However, the cost of replacing the battery is quite high, so this restricts the development of electric vehicles to a large extent.
Balance does not work: Many people think that the battery is used in the middle and late stages of the balance. The actual battery packs are used in the middle and later stages due to different battery capacity losses, resulting in poor capacity. The balance protection board cannot compensate for the battery capacity. The battery pack voltage of each string is the same, but due to the inconsistency of the capacity, the low is often the single string discharge protection and overcharge protection of the battery in the charging and discharging capacity, so the battery capacity is in the low-capacity battery Single string.
The situation where the balance cannot be used: Many people think that the battery pack has a balanced use in the middle and late stages of use. In fact, when the battery pack is used in the middle and later stages, due to the different capacity losses of each battery cell, there is a difference in capacity. The equalization of the protection board cannot compensate for the cell capacity. On the surface, the voltage of each string of the battery pack is the same, but due to the inconsistency of the capacity, the single string cell with low capacity is often over-discharged and over-charged during charging and discharging. Protection, so the capacity of the battery pack is also reflected in a single string of cells with low capacity.
Passive balancing generally discharges the battery with a higher voltage through resistance discharge, and releases the power in the form of heat, so as to obtain more charging time for other batteries. In this way, the power of the entire system is limited by the battery with the least capacity. During the charging process, lithium-ion batteries generally have a charging upper limit protection voltage value. When a certain string of batteries reaches this voltage value, the lithium-ion battery protection board will cut off the charging circuit and stop charging. If the voltage during charging exceeds this value, which is commonly known as "overcharge", the lithium-ion battery may burn or explode.
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