The effect of high-speed discharge balance on consistency issues in lithium battery packs

Charging balance can only solve the problem of fully charging the battery pack, and the actual released power still depends on the smallest capacity battery in the battery pack. Discharge balance solves the problem of unified allocation of all battery capacities and can achieve safe utilization of capacity. This article explains the importance of balanced discharge through the actual balanced discharge data of two series of battery packs.
Consistency issues with battery packs
The consistency issue of battery packs is always a persistent pain in the battery management industry. Consistency issues not only reduce the actual discharge capacity of battery packs, but also affect the power output and battery life of equipment. In severe cases, it may also lead to "thermal runaway" problems, resulting in the occurrence of faults.
Based on the principle of safe discharge, the amount of electricity that a battery pack can release depends on the smallest capacity battery in the battery pack, similar to the "barrel effect". The more strings the battery has, the greater the impact. Taking 100 100Ah lithium-ion battery packs as an example, if the capacity of one battery pack drops to only 80Ah, then the available capacity of the battery pack is only 80Ah, and about 20Ah of the capacity cannot be utilized, which is equivalent to 1/5 of the capacity being wasted and cannot be utilized. It is a great pity. The actual charging and discharging rate of a decaying battery will be higher than the average current of the battery pack, causing attenuation to enter the acceleration channel and form a vicious cycle. The result of a vicious cycle is a rapid decrease in the capacity of the battery pack, accompanied by a serious risk of thermal runaway.
Nowadays, the world is improving the unit capacity of lithium-ion batteries through technological research and development. However, due to technological limitations, progress is slow, and the capacity of existing large capacity battery packs is not fully utilized due to consistency issues. In addition to battery differences caused by production factors, temperature during use, high current charging and discharging, and inadequate battery management can all lead to this problem.
The decrease in discharge capacity corresponds to the same decrease in charging capacity. If it is a vehicle battery pack, it is manifested as severe battery degradation and a significant reduction in range.
The difficulties of battery balancing technology
The only technology that can solve the consistency problem of battery packs with current battery management technology is battery balancing technology. To achieve full utilization of battery capacity, it is necessary to require the battery balancer to support both discharge balancing, charging balancing, and static balancing. In addition, due to the presence of batteries with different capacities, there is a high voltage difference at the end of charging and discharging. Therefore, the battery balancer must also have a wide range of balanced current and efficient energy conversion efficiency, which can achieve efficient balancing and reduce losses during the full utilization of capacity.
The good news is that battery balancing technology with this technical requirement has been developed by the author after years of research and development. After continuous improvement, the performance is getting better and better. A very small voltage difference can obtain a very large balancing current. The design of balancing current within 5A can achieve 1A/13mV; The design of a balanced current of 10-15A can achieve 1A/10mV, thus achieving high-speed balancing. The distinct advantage of this technology is that it supports both high-speed discharge balancing and high-speed charging balancing, which many battery balancer technologies do not have. During high-speed discharge balancing, large capacity batteries release more electricity
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