Wireless BMS Design and Chipset Options

Created: May 28, 2021
Updated: October 10, 2024

Ready to ditch these battery cables and harnesses? A wireless battery management system (BMS) can help you do it.

Despite an automotive chip shortage, plant shutdowns, and long lead times on critical automotive-qualified components, the industry is pushing forward with new advances. Electrification of the vehicle fleet in the US, which happens to be the world’s second largest producer of greenhouse gases, now appears inevitable. The State of California has plans to ban gasoline vehicles by 2035, GM plans to have a zero-emission worldwide fleet by 2040, and the other US automakers have plans to follow suit. China also has plans for a full phase-out of gasoline vehicles by 2035. Things are looking bright if you’re in the green energy business.

One important subsystem in electric vehicles is the battery management system (BMS). This power management subsystem is responsible for several important tasks in electric vehicles:

Monitoring charging and discharging rates
Balancing charge distribution among multiple cells
Predict cell health and perform wear leveling
Identify and alert any safety hazards

Although a lot of the news and literature around BMS designs tends to focus on electric automobiles, a BMS could be used in any type of electrified system that requires balancing charging and discharging from multiple battery cells. The goal in these systems is to maximize the overall battery life, both in terms of the total operational lifetime for a single charging cycle, as well as the lifetime of the battery cells by evenly distributing wear.

At the end of 2020, some companies began announcing a new type of wireless BMS targeting electric vehicles in the consumer market. Now, as of April 2021, the new GM Hummer will include a wireless BMS in partnership with Visteon, a US automotive electronics supplier. Now that some major semiconductor companies are providing wireless BMS chipsets, designers have an opportunity to start building wireless BMS designs for new vehicles. These systems will continue to take prominence as battery OEMs commercialize more advances in battery technology in the coming years.

In this article, we’ll look at some of the newest chipsets that support wireless BMS designs. Although we’ll focus primarily on electric vehicles as this is such a high-demand area, the range of applications for wireless BMS span well beyond consumer and commercial automobiles. Robotic vehicles, aircraft, and drones for use in areas like agriculture, logistics, security, and industrial automation can also benefit from a wireless BMS, and designers can target these areas with innovative wireless BMS products.

Wireless BMS Advantages

Successful, long-term electrification relies on extending battery life, so a BMS in electrified equipment is necessary. So, it’s a fair question to ask, what is the benefit to adding some wireless capabilities to the design?

Fewer cables and wire harnesses: Anytime you can consolidate wiring harnesses in a vehicle or remove them completely, you’re saving valuable space and reducing total weight. The cables used in these systems are also not cheap and are among the heaviest components in an EV, so eliminating these passes savings onto the end buyer.
Modularity: Using a wireless connection eliminates the need for a proprietary cable assembly. Everything around a battery system can be made more modular, allowing 3rd party vendors to innovate and participate in this space.
Simpler maintenance: When there are fewer cables involved in connecting the BMS to the battery cells, the cells and other electronics are easier to access, maintain, and replace when necessary. Using a universal wireless BMS instead of a proprietary wired BMS enables a plug-and-play approach to design and maintenance.
Faster time to market: Working with a universal wireless protocol is simpler than using a mass of cables and wiring harnesses, which may be redesigned for each iteration of each model. Going wireless eliminates this and reduces time to market.

Wireless BMS Architecture

The block diagram below illustrates the general layout of a wireless BMS system. We can see where the wireless channel exists between the battery cells and the main BMS system controller. Each battery cell includes a small module that transmits data to and receives data from the BMS control unit.

Wireless BMS block diagram and architecture.

In this architecture, you have two main portions of the system: a monitoring unit for each battery pack, and a central control unit that interfaces with these monitoring units. Essentially, each battery is a client on the network and reports information back to the main controller. The BMS control unit can still receive data (e.g., vehicle acceleration or other signals) that may indicate more power is required from the battery pack, and the BMS controller can adjust the charging/discharging rate accordingly.

Contrast this with a typical wired BMS controller, which requires running cabling to each cell in the battery pack, creating a mess of wires internal and external to the battery housing. This should illustrate one of the main advantages of a wireless BMS; you’ve effectively cut the amount of wiring required in the system by about 50%. This also eliminates the need to route wiring through the complex structure of a typical electric vehicle, eliminating the need for connectors and fittings between the control unit and the BMS monitor modules.

Wireless BMS Challenges

While a wireless BMS architecture can simplify some systems and provide a number of benefits in terms of efficiency and cost, there are several challenges involved in wireless BMS design and implementation. These include:

Network formation during startup: Ideally, the wireless network used to connect the BMS units on individual cells and the BMS controller should form quickly and without any troubleshooting by the user. This will influence the wireless protocol chosen in the design; note that not all components will use the same protocol, although this is generally a 2.4 GHz protocol (e.g., Bluetooth).
Low latency: Whichever wireless protocol is used, the response time should be relatively fast. This is quite important in an electrified vehicle as battery power may be demanded very quickly during acceleration, causing the batteries to discharge quickly. The BMS control unit needs to know when this occurs and needs to respond quickly by configuring the BMS monitoring unit.
Multipath errors: The space where wireless BMS modules are deployed is very tight, leading to multipath errors and potential for packet errors during operation. In addition, the environment in a vehicle contains multiple noise sources that may interfere over a range of frequencies. The noise environment should be considered during design and when selecting supporting components for isolation.
Low power consumption: This might sound surprising given that BMS modules are connected to a large battery pack, but they will still draw power when the vehicle is not running. This power consumption should be minimized, ideally by eliminating network overhead.

Wireless BMS Chipsets

On the Controller

Much like other components marketed by semiconductor companies, the chips used for wireless BMS products are not much different than their typical non-automotive-qualified ICs. The controller module architecture that hosts the network and captures monitoring data only requires a few components. Automotive-qualified wireless BMS controller MCUs are marketed this way based on industry demand, not because they perform some other special function that can’t be implemented on another MCU. However, these MCUs are highly integrated with the appropriate RF front end, and possibly with a CAN transceiver to interface with the main ECU.

On the Monitor

In some battery management systems, such as for an electric bike, the cell monitoring and balancing chip would normally be mounted on the same board as the rest of the control components. In vehicles, the battery packs are large enough that it makes more sense, just from a cabling perspective, to place these directly on the battery in the architecture shown above.

Typical battery monitoring/balancing chips are available in versions that can support multiple cells while implementing a standard algorithm running on the main controller. However, as of mid-2021, we have yet to see the same level of integration found in other microcontrollers. However, to continue reducing size and weight of these modules, I would expect the active companies in this area to produce an automotive battery balancer IC that integrates lightweight processing and an RF front end for connecting back to the controller unit.

Let’s look at some of the newest components in each area as shown below:

Texas Instruments, BQ79616-Q1

Texas Instruments is already well-known for their BMSb chip family, both for active and passive cell balancing. The BQ79616-Q1 from Texas Instruments is a battery management chip that specifically targets larger battery arrays that require higher balancing current than other solutions. This chip enables up to 240 mA balancing current with 16 series cells, although it can be scaled to higher cell counts with multiple chips. Note that an external MCU and RF section are needed if the BQ79616-Q1 is to be used as part of a wireless BMS. Most importantly for automotive systems, this component aids ASIL-D compliance and ISO 26262 compliance for automotive power systems.

Block diagram with the BQ79616-Q1 BMS monitoring/balancing chip and BQ79616-Q1 used as a wake-up controller.. Source: BQ79616-Q1 datasheet.

Infineon, CYW89820

The CYW89820 from Infineon is a low-cost Bluetooth-enabled MCU SoC specifically designed for automotive systems. This component supports Bluetooth 5.0 core specification with support for BR, EDR @ 2 Mbps and 3 Mbps, and for eSCO, BLE, and LE @ 2 Mbps. This component offers an integrated power regulator (buck converter + LDO), integrated ADC, and power management control unit. Finally, this component offers over-the-air firmware updates, programmable TX Power up to 11.5 dBm, and receiver sensitivity down to –94 dBm (BLE @ 1 Mbps).

CYW89820 Bluetooth 5.0 SoC block diagram. Source: CYW89820 datasheet.

Texas Instruments, SimpleLink MCUs (CC26xx)

The CC26xx MCUs from Texas Instruments include a range of 2.4 GHz-enabled MCUs that can be qualified in automotive applications. The newest product in this line, the CC2662R-Q1, is still in preview, but it will be an automotive-qualified component and is ideal for a wireless BMS operating at 2.4 GHz. An earlier product, the CC2652R, can also be used in wireless BMS designs as it offers multi-protocol support with an integrated PA.

Other Components You Need for Vehicle Power Management

Power management in vehicles and related areas takes a range of components beyond battery monitoring. These systems need their own set of power regulation and interface components to integrate with other systems in a vehicle. take a look at some other components you might need for a wireless BMS product:

Whether you’re designing a wireless BMS for automotive or robotics, you can find the monitor and controller chips your system needs with the advanced search and filtration features in Octopart. When you use Octopart’s electronics search engine, you’ll have access to up-to-date distributor pricing data, parts inventory, and parts specifications, and it’s all freely accessible in a user-friendly interface. Take a look at our integrated circuits page to find the components you need.

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