If the battery cells in the module have poor consistency, when the same current is used for charging and discharging, some batteries will be overcharged or overdischarged, which will greatly shorten the overall cycle life of the battery, and the inconsistency will cause other cells in the battery pack. A domino effect chain reaction occurs in the body. For example, a battery with a cycle life of about 1,000 times, the actual number of cycles in the battery pack is only about 200 times.

　　Consumer batteries, because electrical devices require relatively small power, the power output of a single cell can basically meet the requirements, so it is rarely necessary to use several batteries together. A single battery cell has a low power level. When it encounters high power output applications, such as electric vehicles and energy storage, many cells need to be connected in series and parallel to obtain relatively high output voltage/output power/output current/output power, etc. . As shown in the figure below (Figure 1 and Figure 2), many square cells and cylindrical cells (18650) are combined into one module, and many modules are combined into one pack, which serves as the power source for electric vehicles. Someone on the Internet has disassembled a Tesla modelS, 85Kwh battery pack, 7104 cylindrical batteries produced by Panasonic, each of 444 cells is connected in parallel, a total of 16 groups are connected in series to form a battery pack.

　　Musk dare to do this, not everyone can think so. First of all, Panasonic's small cylinder technology is well-established, and it takes both low cost and consistent performance into consideration. There is a joke that if you use two machines to test Panasonic's batteries, the curves that come out are different, and the first thing you suspect should be your test problem. The battery production process is complex, and there are many factors that affect the consistency of the battery. From front to back, in addition to the consistency of the material itself, there are other things such as batching/stirring/coating/cold pressing/slitting/winding/injecting/forming Wait. In order to improve the consistency of battery shipments, battery manufacturers will also increase the sorting process after formation, and select those batteries with large resistance deviations/severe self-discharges. If the battery core consistency is not good, it will seriously affect the life of the battery and shorten the life of the battery pack. After many times of charging and discharging of a single cell, the reversible capacity will be reduced due to the growth of the surface SEI film/increased side reactions/blocking of the isolation membrane holes. When the capacity decays to 80% of the initial capacity, it will seriously affect The design function of electric vehicles is brought into play. If the battery cells in the module have poor consistency, when the same current is used for charging and discharging, some batteries will be overcharged or overdischarged, which will greatly shorten the overall cycle life of the battery, and the inconsistency will cause other cells in the battery pack. A domino effect chain reaction occurs in the body. For example, a battery with a cycle life of about 1,000 times, the actual number of cycles in the battery pack is only about 200 times. However, if the battery cell consistency is not good, can it be used in groups?

　　The traditional BMS is definitely rejected, but not necessarily if it is SDB (software defined battery). The traditional BMS comes in with a charging cable, charges/records/stops all the batteries, and then outputs. If the consistency of the cells is poor, the problems described above will occur one by one. To go one step further, if we expand our minds a little bit, I install two batteries in my battery pack, one for low-rate discharge conditions during low-speed cruising, and the other for high-speed emergency stops. The high-rate discharge conditions. Different battery cell systems have different characteristics. The energy density/power density/cost/lifetime/flexibility and other indicators that are often considered conflict with each other. If you need to use different system batteries in the same module, you can match a battery with outstanding comprehensive performance. Products, traditional BMS is more difficult.

　　Microsoft feels that this can be done like this: Add a charge and discharge management microdevice (smartswitching circuitry) to each battery to collect the charge and discharge voltage/current/resistance of each battery, realize intelligent shunt allocation, and make each battery charge The discharge situation is close to that of a single cell, maximizing the use value of the cell. The main difficulty of this battery management mode is the analysis and current allocation after collecting these data. Microsoft has developed a more complex algorithm for it, and the battery pack using this battery management mode is Softwaredefinedbattery.

　　More importantly, this battery management mode can realize the mixed management of different chemical systems. There are many ways to store energy, with different advantages and disadvantages. With different voltages/different resistances/different charge-discharge rates, can these batteries work properly if combined together? In this regard, Microsoft used SDB to conduct an experiment and got good results (BatteryManagementfor2-in-1s). Also, in smart watches, flexible solid-state batteries can be assembled with the strap, and the polymer lithium battery under the dial can better extend the standby time. This requires SDB to better regulate the solid-state battery and the liquid battery. 'S cooperated.