Let’s talk about the current solutions and applications of wireless BMS

I have been on a business trip recently, so I have less free time. I really gained a lot from traveling to the site, and I have a deeper understanding of the specific details of certain products.

This time I want to talk about the content of wireless BMS. Regarding this part, I believe everyone has come into contact with wireless BMS implementation solutions from various manufacturers before, such as TI’s wireless introduction:

To give a specific example, TI's wireless solution is implemented as follows (picture from TI's official website). Each acquisition board has an AFE for normal cell monitoring, and then the acquisition board and the main control board are connected wirelessly.

The main goal of the wireless BMS solution is to make the communication between the BMS acquisition board and the control board wireless . The following figure shows the comparison of the architecture of daisy chain communication and wireless communication (from the TI official website): The current BMS on electric vehicles In the solution, the main communication between the acquisition board and the control board is daisy chain communication. The specific protocol is bound to each manufacturer's AFE, but externally it is in the form of differential communication, and a network transformer is required for isolated transmission; after switching to a wireless solution, The acquisition board can remove the network transformer, signal connector and wiring harness, but adds a wireless MCU, such as the CC2662 in the TI solution as shown below. In addition, the wireless protocols are currently bound to each manufacturer and are incompatible with each other.

There are already many manufacturers that can provide wireless BMS solutions, such as TI, ADI, Visteon, etc. This article will not go into the details of specific wireless protocols. In addition, I have also seen a wireless BMS solution called Dukosi that is very special. Using near-field wireless communication (NFC) technology, communication can be established by placing the back of the acquisition board and control board close to the same line, and the line and the single board are in the form of non-electrical contact. (The picture below comes from the Internet)

Let’s take a look at the advantages and disadvantages of wireless BMS (the picture below is from TI’s official website). There is an important factor that is not considered in the table, namely cost . At present, everyone has seen that wireless BMS has not been widely promoted in electric vehicles (basically everyone is waiting and watching. and pre-research), the important reason is the cost issue; as mentioned earlier, the wireless BMS solution adds a wireless MCU, and its cost cannot be absorbed by reducing network transformers and wiring harnesses at this stage.

However, wireless BMS does have mass production applications at this stage. Huawei has used a product called iBAT in base station energy storage. It is a wireless BMS acquisition board. Each acquisition board collects lead-acid batteries. You can see that the board is powered by 12V, which comes from the battery itself.

The internal PCBA is shown in the figure below. There is only one sampling input connector on the board. The external communication method is ZigBee wireless communication. You can also see the PCB wiring antenna on the board, which uses TI's CC2538 wireless MCU.

In Huawei's application, since each lead-acid battery is relatively large in size and difficult to group into groups, each battery is equipped with its own collector. This increases the size of the communication harness, so wireless is used here. The BMS solution has more advantages.

As can be seen from the above, if there is an application later that requires a separate collection board for each battery cell, the advantages of using a wireless BMS will be fully reflected; for example, the single battery cell that Datang NXP has been promoting Sampling chip DNB1168 (picture from Datang NXP official website), it only samples a single cell and has electrochemical impedance measurement function, but in this case there will be a lot of wiring harnesses for communication between AFEs, so using a wireless communication solution is Good choice.

In addition, as technology evolves, I believe the cost of wireless chips will also come down; some companies are now working hard to combine AFE and wireless communication functions, which may also lead to cost reductions.

Summarize:

All of the above are for reference only.