Basic requirements and functional characteristics of BMS for power exchange and leasing.

1) Low cost and high reliability

Just now we talked about the iron tower, the current mainstream voltage platform for battery replacement is generally 48V and 60V, and the battery types are ternary, including lithium iron phosphate. The major mainstream brands are still dominated by lithium iron phosphate. The lithium iron phosphate battery has higher safety performance and longer life. The disadvantage is that the low temperature performance is worse than that of the ternary lithium battery. According to the application scenarios of battery replacement, there are some special requirements for the BMS. In addition to the basic functional requirements, the first requirement is low cost and high reliability. This is a very contradictory thing, both high reliability and low cost. Our battery management system is also very demanding for passenger cars, commercial vehicles, including large-scale energy storage, but it accounts for a relatively large amount, but for two-wheeled vehicle battery packs, generally a few hundred yuan to more than one thousand yuan Renminbi, if you build a battery management system worth five hundred yuan or more, you can definitely achieve reliability, but your cost is very high, and operators, including ordinary people, are not very accepting, so this is a contradiction. Therefore, when we focus on this industry, we also see that this is very challenging, how to achieve high returns at low cost. Our company Litongwei has been in this industry for 16 years. There are large-scale projects in the energy storage field and the electric transportation field.

2) Basic collection and protection functions

I just talked about the general collection of protection boards, voltage, temperature, and current. As 48V and 60V battery packs are relatively low voltage, insulation monitoring is generally not performed. Of course, we have individual customers who require us to monitor the insulation status of the case with the positive and negative electrodes under the 48V platform and have a protection function.

3) Positioning and remote communication

Because many of the current battery exchange fields are applied to couriers, it is necessary to monitor the trajectory and mileage of the couriers. In addition, the couriers need to see the power through their mobile phones, rather than the original estimation. When the original lead-acid battery did not show the remaining power, it can only be estimated that it can run about 40 kilometers, but now the battery swap field requires the remaining power to be displayed. Running 20 kilometers and 50% of the remaining power indicates that you can continue to run 20 kilometers, and it shows that you need to find a nearby switchgear for battery replacement after the last few kilometers.

4) Low-power sleep

Early lead-acid batteries do not need overcharge and overdischarge protection, and there is no power consumption problem, but lithium batteries need to be protected. The semiconductor circuit is connected to the battery pack for a long time, and the power consumption of its own milliampere level, after a few months If the battery itself is in an undervoltage state, it may cause permanent damage to the lithium battery. It was originally responsible for the protection function, but due to the serious power consumption problem, the battery cannot be repaired. At present, we can achieve microampere, 50 microampere, forty microampere class, and some projects can achieve more than ten microampere class, to ensure that the battery pack is in a normal state after being placed for more than half a year in the case of insufficient power. .

5) Charging interactively with the switch cabinet

This is very, very important. We learn from the interactive development of transportation electric buses, electric passenger cars and charging piles. We have a lot of experience.

6) Local storage of alarm and protection information

This is equivalent to a black box. When there is something or an accident, you can call this out and see what happened at that time.