The essentials of balancing charging of lithium-ion battery packs and the principle of balancing charging of lithium-ion battery packs

Balance is the key technology to manage the difference of battery cells. For the use of lithium-ion batteries in groups, each lithium-ion battery requires charging over-voltage, discharge under-voltage, over-current, and short-circuit protection, and the entire group of batteries must be realized during the charging process. For the problem of balancing charging, this article will first introduce the essentials of balancing charging of lithium-ion battery packs and the principles of charging balance. What is charge balance? Charge balance, abbreviated as equal charge, is a charge that balances the characteristics of a battery. It means that the battery terminal voltage is not balanced due to individual differences in the battery, temperature differences, etc., in order to prevent such dissatisfaction. To balance the deterioration of the trend, it is necessary to increase the charging voltage of the battery pack and perform activation charging on the battery to balance the characteristics of each battery in the lithium-ion battery pack and delay the maintenance of battery life. Commonly used balancing charging techniques include constant shunt resistance balancing charging, on-off shunt resistance balancing charging, average battery voltage balancing charging, switched capacitor balancing charging, step-down regulator balancing charging, inductive balancing charging, etc. When charging a group of lithium-ion batteries in series, you should ensure that each battery is charged in a balanced manner, otherwise the function and life of the entire group of batteries will be affected during use. The existing single-cell lithium-ion battery protection chips do not contain balanced charging control results. The balanced charging control results of multi-cell lithium-ion battery protection chips need to be connected to the CPU; it is realized through serial communication with the protection chip, and the protection circuit is enlarged. Pang Hong’s gentle design is difficult, reduces the efficiency and reliability of the system, and increases power consumption. The essentials for balancing charging of lithium-ion battery packs. In the environment where the production of lithium-ion battery packs is relatively long and the storage time is relatively long, due to the difference in the static power consumption of each circuit of the protective plate and the difference in the self-discharge rate of each battery cell, the formation of the entire battery string The voltage is divergent. The balance has the effect of balancing the voltage on the lithium-ion battery pack, so that it can reach the full charge and discharge function of the battery pack capacity, so that the battery pack can exert its maximum function. Commonly used lithium-ion battery pack balancing charging techniques include constant shunt resistance balancing charging, on-off shunt resistance balancing charging, average battery voltage balancing charging, switched capacitor balancing charging, step-down regulator balancing charging, inductive balancing charging, etc. When charging a group of lithium-ion batteries in series, you should ensure that each battery is charged in a balanced manner, otherwise the function and life of the entire group of batteries will be affected during use. 1. Attach a parallel balance circuit to each single cell of the lithium-ion battery pack to achieve the purpose of shunting. In this mode, when a battery reaches full charge first, the balancing device can prevent it from overcharging and convert the excess energy into heat, and continue to charge the battery that is not full. The method is simple, but it will cause energy loss and is not suitable for fast charging systems. 2. Before charging, each cell is discharged to the same degree through the same load one by one, and then constant current charging is performed to ensure a more accurate balance between the cells. However, for battery packs, due to the physical differences between the individual cells, it is difficult to achieve exactly the same ideal results after deep discharge of each cell. Even if the same result is reached after discharge, a new imbalance will appear during the charging process. 3. Timing, sequencing, and individual testing and symmetrical charging of the single cells in the lithium-ion battery pack. When charging the lithium-ion battery pack, it can guarantee that each lithium-ion battery in the battery pack will not generate an overcharge or over-discharge environment, thus ensuring that each battery in the lithium-ion battery pack is in normal operation status. 4. Using time-sharing principle, through the control and switching of switch components, special current flows into the battery with relatively low voltage to achieve the goal of balanced charging. The efficiency of this method is relatively high, but the control is huge. 5. Use the voltage parameters of each battery as a balancing tool to make the voltage recovery of each battery consistent. During balance charging, the capacitor is connected to two adjacent batteries through a control switch, taking over the charging of the high-voltage battery, and then discharging to the low-voltage battery until the voltages of the two batteries tend to be the same. This kind of balance method can better deal with the problem of battery voltage unbalance, but this method is mainly used in places with a small number of batteries. 6. The whole system is controlled by a single-chip microcomputer, and the single battery has an independent set of modules. The module will charge each single battery separately according to the set measures, and will automatically disconnect after the charge is completed. The method is relatively simple, but when the number of single cells is large, the cost will be greatly increased, and it is also unfortunate for the reduction of the system size. Lithium-ion battery pack charging balance principle The number of single-cell lithium-ion battery protection chips is determined according to the number of lithium-ion battery pack batteries, and they are used in series to separately protect the corresponding single-cell lithium-ion battery charge and discharge, overcurrent, and short-circuit conditions. 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