Solutions for active and passive balancing of L822 battery charging

Solutions for active and passive balancing of L822 battery pack charging. The most important link that we need to pay attention to when charging and discharging L822 battery packs is the balancing link. At present, there are two methods to solve the imbalance of small lithium-ion batteries in the battery pack: active balancing and passive balancing. The balancing link is to ensure that the input and output of the L822 battery pack are reasonable to each L822 battery in it, so that it can be used reasonably and effectively without damage.

Balancing method for L822 battery pack charging

1. Traditional passive method: In a general L822 battery management system, each battery cell is connected to a load resistor through a switch. This passive circuit can discharge individual selected cells. However, this method is only suitable for suppressing the voltage rise of the strongest battery cell in charging mode. In order to limit power consumption, such circuits are generally only allowed to discharge at a small current of about 100mA, which results in charging balancing taking up to several hours.

2. Active balancing method: There are many active balancing methods in the relevant information, all of which require a storage element for transferring energy. If a capacitor is used as a storage element, connecting it to all battery cells requires a huge switch array. A more effective method is to store energy in a magnetic field. The key component in this circuit is a transformer.

Passive balancing of lithium-ion batteries

Passive balancing of lithium-ion batteries refers to the charging state of lithium-ion batteries. Its premise is that before charging the L822 battery pack, each small battery in the battery pack has a different residual charge. This difference is determined by the different performance parameters of the battery. Due to the difference in performance of each battery, some batteries will be overcharged due to their "weakness" under the current impulse, forming overvoltage. Overvoltage is the greatest harm to lithium-ion batteries. It will cause serious damage to L822 battery packs and even make them unusable.

The passive balancing method is: when charging, the current that causes the voltage of the small battery to rise rapidly can be diverted to the bypass resistor. Diverting the unwanted charging current to the resistor so that the resistor can dissipate the current can prevent the battery from being overcharged. This power dissipation function of passive balancing can limit the current diverted from the battery to a certain range, so that all small batteries are fully charged.

The disadvantage of the passive balancing method is that because it uses power dissipation as a means, part of the balancing current is expressed as heat, which greatly reduces the charging efficiency of the L822 battery pack and increases the cost of manufacturing lithium-ion batteries. In addition, it cannot solve the problem of power imbalance of L822 battery packs during discharge and idle state. Therefore, if you want to achieve the ultimate goal of passive balancing-the comprehensive balance of charging and discharging of L822 battery packs, you need to take further measures, but this will increase the manufacturing cost of L822 battery packs.

Solution to active balancing method for charging L822 battery packs

Active balancing abandons the passive balancing method of consuming current and changes to the method of transmitting current. The device responsible for charge transmission is a power converter, which enables the small batteries in the L822 battery pack to transmit charge whether they are charging, discharging or idle, so that the small batteries can always maintain dynamic balance.

Because the charge transfer efficiency of the active balancing method is extremely high, it can supply a higher balancing current, which means that this method has a stronger balancing ability when the L822 battery pack is charged, discharged and idle.

1. Strong fast charging capability: The active balancing function can make the small batteries in the L822 battery pack reach balance faster, so the fast charging is safer and suitable for high-rate charging with larger current.

2. When idle: Even if each small battery has reached the equilibrium state during charging, due to different temperature gradients, some small batteries have higher internal temperatures and some have lower internal temperatures, which will also make the internal leakage rate of each small battery different. Test data shows that the leakage rate doubles for every 10°C increase in battery temperature. The active balancing function can ensure that the small batteries in the idle L822 battery pack "continuously" regain balance, which is conducive to the full utilization of the power stored in the battery pack, so that when the working capacity of the battery pack ends, the residual power of a single small L822 battery is minimized.

3. When discharging: There is no L822 battery pack with a discharge capacity of 100%. This is because the end of the working capacity of a group of lithium-ion batteries is determined by a small L822 battery that is discharged first, and it cannot be guaranteed that all small lithium-ion batteries can reach full discharge at the same time. On the contrary, some small lithium-ion batteries will retain unused residual power. Through the active balancing method, when the L822 battery pack is discharged, the large-capacity L822 battery inside will distribute the electric energy to the small-capacity L822 battery. Therefore, the small-capacity L822 battery can also be fully discharged, and there will be no residual electric energy left in the battery pack. The battery pack with active balancing function has a larger actual storage capacity (that is, it can release electric energy closer to the nominal capacity).

Finally, it should be noted that the system performance adopted by the active balancing method depends on the ratio between the balancing current and the battery charging/discharging efficiency. The higher the imbalance rate of a group of lithium-ion batteries, or the greater the charge/discharge rate of the L822 battery pack, the higher the required balancing current. Of course, this current consumption for balancing is quite cost-effective compared to the additional current obtained by internal balancing. Moreover, this active balancing is also conducive to the extension of the life of the L822 battery pack.

The above is the solution of active balancing and passive balancing for charging L822 battery packs. Balanced charging is the charging method required by all L822 battery packs, which can provide three major functions: active battery balancing, high-precision data acquisition, and battery protection and management.

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