Lithium battery management technology -Lithium - Ion Battery Equipment

Decrypt the new lithium battery management technology, lithium batteries also need big data! -Lithium - Ion Battery Equipment

For consumer batteries, because the power consumption of electrical devices is relatively small, the power output of a single battery core can basically meet the requirements, so several batteries are rarely used together. The power of a single battery cell is small. When encountering applications with high power output, such as electric vehicles and energy storage, it is necessary to connect many cells in series and parallel to obtain relatively high output voltage/output power/output current/output power, etc. .

Many square cells and cylindrical cells (18650) are combined into one module, and many modules are combined into one pack to serve as the power source for electric vehicles. Someone on the Internet has dismantled the Tesla model S, the 85Kwh battery pack, 7104 cylindrical cells produced by Panasonic, and every 444 cells are connected in parallel, a total of 16 groups, and the groups are connected in series to form a battery pack.

Master dares to do this, but not everyone can think so. First of all, Panasonic's small cylinder technology is superb, taking into account low cost and consistent performance. There is a joke that if you use two machines to test Panasonic batteries and the curves are different, the first thing you should suspect is your test problem. The battery production process is complex and there are many factors that affect the consistency of the battery cells. From front to back, in addition to the consistency of the material itself, there are also factors such as batching/stirring/coating/cold pressing/slitting/winding/liquid injection/formation wait. In order to improve the consistency of battery shipments, battery manufacturers will also add a sorting process after formation to select batteries with large resistance deviations/serious self-discharge. If the consistency of the battery core is not good, it will seriously affect the service life of the battery and shorten the service life of the battery pack. After a single battery cell has been charged and discharged for many times, the reversible capacity will be attenuated due to reasons such as the surface SEI film rising/increased side reactions/isolation film holes being blocked. When the capacity attenuates to 80% of the initial capacity, it will be seriously affected. Electric vehicles are designed to function. If the battery cells in the module have poor consistency and use the same current for charging and discharging, some batteries will be overcharged or overdischarged, which will greatly shorten the overall cycle life of the battery. Inconsistency will cause other cells in the battery pack to fail. A domino effect chain reaction occurs. For example, a battery cell with a cycle life of about 1,000 times will only have about 200 actual cycles in the battery pack. However, if the consistency of the battery cells is not good, can they still be used in groups?(Lithium - Ion Battery Equipment)

Traditional BMS will definitely reject it, but if it is SDB (software defined battery), it is not necessarily the case. A traditional BMS comes with a charging cable, charges/records/stops all batteries, and then outputs it. If the consistency of the battery core is poor, the problems described above will occur one by one. Going a step further, if we open up our imagination a little more, I install two kinds of batteries in my battery pack, one is used to deal with low-rate discharge conditions during low-speed cruising, and the other is used to deal with high-speed emergency stops. high rate discharge conditions. Different battery core systems have different characteristics, and often-considered indicators such as energy density/power density/cost/lifetime/flexibility are also conflicting with each other. If you want to use different system battery cells in the same module, you need to match them with one with outstanding comprehensive performance. Products, traditional BMS is more difficult. Microsoft believes that this can be done by adding a charging and discharging management microdevice (smartswitching circuit) to each battery, collecting the charging and discharging voltage/current/resistance of each battery, and realizing intelligent shunt allocation, so that the charging and discharging of each battery cell can be effectively controlled. The discharge situation is close to that of a single battery core, maximizing the use value of the battery core. The important difficulty of this battery management mode lies in the analysis and current allocation after collecting this data. Microsoft has developed a relatively complex algorithm for this and calls the battery pack using this battery management mode Softwaredefinedbattery.



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