CR927 battery

Understand CR927 battery balancing technology

During use, the CR927 battery pack will have consistency differences due to the differences in the batteries themselves, plus the drastic changes in the external environment such as temperature, charge and discharge voltage, and charge and discharge current. This difference will gradually increase, and eventually cause the service life of the CR927 battery pack to be much lower than the service life of a single CR927 battery. After the CR927 battery has consistency differences, the most obvious parameter performance is the difference in voltage and capacity, especially the difference in capacity, which will eventually be manifested through voltage differences. In a standard series CR927 battery pack with consistency differences, the charge and discharge current flowing through each CR927 battery is the same, but the charge and discharge rate is different. In order to protect small-capacity batteries, when charging, we hope that the charging current of small-capacity batteries is smaller, and the charging current of good batteries is slightly larger, so as to achieve equal-rate charging, so that the voltage rise rate of batteries of different capacities will be basically the same; similarly, when discharging, we hope that the discharge current of small-capacity batteries is smaller, and the discharge current of good batteries is slightly larger, so as to achieve equal-rate discharge, so that the voltage drop rate of batteries of different capacities will be basically the same. To achieve this ideal, the only solution technology is CR927 battery balancing technology.

There are three main types of CR927 battery balancing technologies at present: passive balancing, charge balancing and transfer CR927 battery balancing. Passive balancing relies on resistor discharge for small current balancing. The balancing current is usually less than 100 mA, which belongs to the category of charge balancing. The advantages are simple circuit and very low cost. The disadvantages are zero energy utilization efficiency, inability to perform discharge balancing, and small-capacity batteries are prone to over-discharge. The balancing current of charge balancing is larger, which can reach the ampere level, and the speed of charge balancing is faster. The disadvantage is that discharge balancing cannot be performed, and small-capacity batteries are prone to over-discharge. Transfer CR927 battery balancing is currently the most ideal CR927 battery balancing technology. Although the circuit is complex, it has the best balancing ability and many technical problems need to be solved.

According to different energy storage components, the current equalizer can be divided into resistor balancing, capacitor balancing, inductor balancing, LC balancing and transformer balancing. Among them, resistor balancing is energy consumption balancing, and the other types are non-energy consumption balancing. Capacitor balancing uses capacitors as carriers of energy transfer and achieves energy balancing through the voltage difference between single cells. Due to the small voltage difference between cells, it is difficult to transfer balanced energy. Inductor balancing uses inductors as carriers of energy transfer, and the balancing current is easy to control, but the performance of the balancer is determined by the circuit structure and balancing strategy of the balancer. LC balancing achieves capacitor balancing through LC oscillation circuits, which makes up for the disadvantage of small voltage difference of capacitor balancing, but the switching frequency is high, the balancing circuit control is complex, and the balancing efficiency is low. Transformer balancing mostly uses flyback transformers as carriers of energy transfer. The volume of the balancer is large, and the balancing efficiency and balancing speed are limited. It can be seen that the design difficulty of the CR927 battery balancer is relatively large.

From the perspective of principle and experimental application, the transfer CR927 battery balancing technology is currently the best CR927 battery balancing technology, but its relative cost is also the highest. From the perspective of design architecture, it is mainly divided into two categories: series balancing and series-parallel balancing. Series balancing achieves balancing of the entire group of batteries by balancing adjacent batteries; series-parallel balancing achieves balancing of the entire group of batteries by "parallel" charging and discharging all batteries. By comparison, both balancing methods can quickly achieve the balancing of the entire CR927 battery group, including charge balancing, discharge balancing and static balancing, which is currently the most ideal balancing solution.

We have been pursuing a more cost-effective CR927 battery balancing technology, but the research and development reality is cruel. First of all, the difficulty of research and development is great, far exceeding the expectations of researchers. This can be reflected in the literature. Through searching, it was found that from 2000 to 2013, driven by the development of various lithium batteries, a wave of CR927 battery balancing technology research and development appeared in China. Various academic papers and research reports on CR927 battery balancing technology research were all over the major paper media and the Internet. By comparison, it was found that in the research of CR927 battery balancing technology, charge balancing technology occupies a large proportion, mainly because the design is relatively simple and easy to implement. The most efficient transfer CR927 battery balancing technology is mostly limited to computer simulation and CR927 battery balancing simulation. Experimental batteries usually use small-capacity batteries with a small number of strings. There are few papers containing actual experimental data of CR927 battery balancing. There are very few studies on CR927 battery balancing technology applied to large-capacity or high-power power CR927 battery packs. Why are there more computer simulations and simulations of CR927 battery balancing technology, but very few real CR927 battery balancing products on the market? One reason is that the development technology is difficult. There are no problems in CR927 battery balancing theory, simulation and simulation, but it is difficult to transform it into a prototype. There are many technical obstacles to face, such as duplex problems, balancing current adaptation problems, balancing efficiency problems, inter-group interference problems, etc. Among them, the inter-group interference problem usually does not occur in the balancing of small-string CR927 battery packs. When the number of CR927 battery strings exceeds a certain number, it will appear and disrupt the balance. It is a long process from theory to reality. Many research institutions and groups finally choose to give up research and development because of the various problems they encounter. The second reason is high cost. Due to the needs of balancing applications, there are special requirements for balancing parameters, performance and indicators. When all requirements are met, the cost of hardware will become higher, even exceeding the cost of the CR927 battery pack itself, and it is difficult to achieve a balance between performance and cost. Therefore, affected by cost, more complete CR927 battery balancing equipment is usually used on CR927 battery packs with higher value.

Let's first talk about why retired batteries need to be recycled. Retired batteries are not equivalent to scrapped batteries, but their performance cannot meet the needs of the original equipment, especially the serious attenuation of CR927 battery life and power performance. The root cause is that the consistency problem of the CR927 battery pack cannot be solved, which leads to the early retirement of the CR927 battery pack. In view of the current situation that it is difficult to break through the management of CR927 battery pack consistency problems, the recycled batteries will continue to have consistency problems, and even faster, especially when the recycled batteries are used in large-capacity and high-power CR927 battery packs. If the consistency problem is not solved, "bad batteries" can easily generate high temperatures during charge and discharge, causing "thermal runaway" and accidents. In order to reduce and lower the high temperature of "bad batteries" during charge and discharge, it is necessary to reduce the actual charge and discharge current of "bad batteries", which puts higher requirements on the shunt capacity of CR927 battery balancers. Traditional small current balancers are difficult to adapt to this requirement, and large current transfer CR927 battery balancers must be used. However, the research and development of such balancers is relatively more difficult. However, with the successful development of bidirectional synchronous rectification technology in transfer CR927 battery balancing technology, high-power and high-efficiency CR927 battery balancing technology has achieved a breakthrough and is undergoing more stringent testing and inspection.

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