For wireless BMS systems, high efficiency, long service life, and stable and reliable performance are the three main design goals. This article mainly talks about it.
To achieve these goals, BMS systems need to monitor various battery packs and individual cell data in real time, including temperature, difference of voltage vs current data. This data is then sent via the isolated CAN communication bus to the host controller for further processing.
1. What is a wireless BMS
To date, the communication connection from the host controller to the single cell and battery pack has been achieved mainly by wire. Therefore, BMS systems generally require a large amount of wiring to complete communication connection and isolation, which is not only costly for BMS systems, but also difficult to implement.
If the cable in the battery pack breaks due to an accidental accident, the entire battery pack needs to be replaced. In order to solve the above problems, a new battery management system has emerged that uses wireless communication methods, which is the wireless battery management system wireless BMS.
The wireless battery management system uses the ISM band, the 2.4GHz frequency band, for wireless data communication, replacing the traditional wired cable connection.
2. What is the use of a wireless BMS
Wireless BMS can monitor the voltage and temperature of the cell pack of the battery module, as well as activate cell balancing, thus improving battery life. Use wireless communication to co-manage each cell and module, while supporting remote software feature updates, making battery management more flexible and easy. Overall, this is basically no different from the general BMS.
From an EV perspective, the strategic value of wireless battery management system is:
- Reduced harness weight: Wireless BMS helps improve the range of electric vehicles by reducing the weight of the entire battery system by reducing the use of wiring harnesses.
- Remote update support: The underlying architecture supports software functionality updates, and battery cells can also be easily upgraded. Remote upgrade capability enhances system flexibility.
- Simplified processes: Reducing the use of wire harnesses and connectors simplifies the assembly process and improves production quality and efficiency.
- Flexible solution to the battery life cycle echelon problem: Wireless BMS considers the secondary use of the batteries, so that the battery pack can be easily and conveniently reused after retirement, helping to improve the battery's service life and sustainability.
In the era of module design, wireless BMS is generally better. But in the era of CTP and even CTC, wired and wireless do not seem to have a big gap.
3. The benefits and disadvantages of wireless BMS
● Wireless BMS has the following advantages:
- Greater security and reliability
- Lower manufacturing costs: This cost includes not only the material cost of the cable and related accessories, but also the design cost of the cable.
- More flexibility in battery layout and scalability.
- Lower overall weight: This is because wireless BMS systems no longer require a lot of wiring, so they don't need a lot of cables, connecting terminals and related materials. The overall weight will be lighter.
- Longer range: Due to the drastic reduction in weight, you will be able to travel longer distances per full battery charge.
- Smaller system: Wireless BMS systems will have smaller battery packs at the same capacity.
- Simpler system maintenance: Since the use of wired cables is significantly reduced, it is easier to inspect and replace individual cells in the battery pack.
● What are the challenges of wireless BMS
A new era of wireless battery management systems that focus on safety tasks. The full benefits of battery management system technology can only be achieved if safety is ensured throughout the EV battery life cycle, from the device to the network. From this perspective, security requires a system-level design philosophy, including processes and products.
Wireless BMS is applied to the entire battery pack, and its electromagnetic compatibility is a difficult problem. Stability of anti-interference is also a challenge. Once the wireless transmission of the wireless BMS is disturbed, the protection response to the lithium battery pack cannot be made in time.
4. Why choose a wireless BMS
● Structurally safer
From now on, we no longer need to worry about the PACK welding voltage acquisition signal line of the lithium battery pack. Simply connect them in series or parallel, greatly reducing the complexity of wiring. In addition, and more importantly, this connection method avoids various hidden dangers caused by wiring harness problems.
● Increased energy density
Reduce the wiring harness of the lithium battery pack, so that the space utilization efficiency of the battery pack is improved, the weight and volume are improved, and the energy density is also improved.
● The cost of the overall PACK is reduced
Reduces the cost of wiring harness connection plug-ins, monitoring modules and other components.
● Smarter and simpler
Through CAN bus communication, wireless transmission, the monitoring and management of battery SOC, voltage, current, temperature, operating status and other parameters is more intelligent.
Wireless BMS can collect battery data, not only predict battery performance, but also track and monitor vehicle production, warehousing and transportation, after-sales maintenance, battery recycling, etc., and the entire life cycle of lithium battery packs will be digitized.
5. Is it necessary to use a wireless BMS
As far as the current BMS scheme is concerned, it is not necessarily, the main thing is the cost. At present, we see that wireless BMS has not been widely promoted, and the important reason is the cost problem. The wireless BMS solution adds a wireless MCU, and its cost cannot be absorbed by reducing network transformers and wiring harnesses at this stage.
On the other hand, wireless BMS can be better applied to the echelon utilization (module level) after the battery pack is retired in the era of module technology. But with the higher integration of battery packs, the module era is also being phased out, and there are still too many uncertainties in everything.
From a technical point of view alone, battery management system is undoubtedly worth studying, not only component manufacturers. However, from a commercial and industrial point of view, this is still a contest of costs and benefits, and the significant advantages of wireless cannot be seen in the current BMS integration solution.
The essence of wireless BMS is to use wireless communication technology to get rid of those cumbersome wiring harnesses. This technology is realized by a small wireless chip, which can be seamlessly integrated with existing acquisition chips and master controller chips to form a new BMS board.
In other words, we can simplify the structure of the battery management system and improve the reliability and stability of the entire system through this wireless communication technology.
Since there is no physical connection such as a wiring harness, there is no need for additional electrical insulation treatment, which further reduces the component cost of wireless BMS in the hardware circuit, and the complexity of design and assembly.