Decrypt new battery management technology, battery also big data!

As shown in the following figure (Fig. 1 and Fig. 2), many square cells and cylindrical cells (18650) are combined into one module, and many modules are combined into a pack to serve as a power source for electric vehicles. Some people have disassembled the Tesla model S, 85Kwh battery pack, and the 7104 section Panasonic's cylindrical battery core. Each group of 444 sections is 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, not everyone can think so. First of all, Panasonic's small cylindrical technology is pure, with low cost and consistent performance. There is a joke that if you use two machines to test the Panasonic battery, the curve is different. The first thing you suspect should be your test problem. The battery production process is complicated, and there are many factors affecting the consistency of the battery. From front to back, in addition to the consistency of the material itself, there are also such as compounding/stirring/coating/cold pressing/striping/winding/injection/forming. Wait. In order to improve the consistency of battery shipments, battery manufacturers will also increase the sorting process after the formation, and select those batteries with large resistance offset/severe discharge. If the cell consistency is not good, it will seriously affect the life of the battery and shorten the service life of the battery pack. After many times of charge and discharge, the reversible capacity will be attenuated due to the increase in surface SEI film growth/side reaction/blocking of pores, and the capacity will be seriously affected when the capacity decays to 80% of the initial capacity. The design features of electric vehicles play. If the battery cells in the module are in poor consistency, when using the same current for charging and discharging, it will cause overcharging or overdischarging of some batteries, which will greatly shorten the overall cycle life of the battery. Inconsistency will lead to other orders in the battery pack. The body has a chain reaction of domino effect. For a battery with a cycle life of about 1000 times, the actual number of cycles in the battery pack is only about 200 times. However, if the cell consistency is not good, can the group still be used?

The traditional BMS is definitely rejected, but if it is SDB (software defined battery), it is not necessary. A traditional BMS charging cable comes in, charging/recording/ending all the batteries, and then outputting them. If the cell consistency is poor, the problems described above will occur one by one. Further, if our brain hole is bigger, I install two batteries in my battery pack, one for low-rate discharge during low-speed cruising and the other for high-speed emergency stop. High rate discharge conditions. Different cell systems have different characteristics. The energy density/power density/cost/life/flexibility indicators that are often considered are also conflicting. If you need to use different system cells in the same module, match a comprehensive performance. Products, traditional BMS is more difficult. Microsoft feels that this can be done by adding a smart switching circuitry to each battery, collecting the charge/discharge voltage/current/resistance of each battery, enabling intelligent shunting to make each cell The charge and discharge situation is close to the single cell, maximizing the use value of the cell. The main difficulty of this cell management mode is the analysis and current distribution after collecting the data. Microsoft developed a more complicated algorithm for it and will use the battery pack of this battery management mode as Software defined battery.

More critically, this battery management mode enables mixing management of different chemical systems. There are thousands of ways of storing energy, and the advantages and disadvantages are not the same. Different voltages/different resistances/different charge/discharge rates, can these batteries work together and work properly? In this regard, Microsoft used SDB to conduct an experiment and got good results (Battery Management for 2-in-1s). In addition, in the smart watch, the flexible solid battery can be assembled with the strap, and the polymer Lithium Battery under the dial can better extend the standby time, which requires the SDB to better regulate between the solid battery and the liquid battery. The match has been made.

As for the introduction of so many charge and discharge micro-devices, the problem of money (cost), "We believe the BoM cost and space requirement of our SDB soluTIon will not be significant". In the future, this SDB system will also be connected to the vehicle IoT, understand your personal behavior and user schedule, etc., to serve your travel. Ah, our battery is also big data Internet of Things, and it is foreign.