22-01-2021 | | By Sam Brown
Recently, Texas Instruments revealed its wireless battery system that they claim will help automotive manufacturers of electric vehicles. What does this system allow for what advantages does it provide, and is it a good idea?
Recently, Texas Instruments famous for their range of calculators and semiconductor products has revealed their new battery management system for electric vehicles. Unlike a traditional BMS, the new system removes the need for any control lines or sensing on the power cable itself and utilizes a wireless connection between the vehicle and charging station to transfer information.
The specially designed protocol allows for all data regarding the vehicle's battery to be transmitted, and the system can provide information on more than 100 cells in milliseconds. Also stated by Texas Instruments is that the power consumed by the wireless chips is very low. According to a TI presentation, the main node of the system consumes 294uW while the individual devices consume 200uW.
Furthermore, the new system can work with multiple battery configurations, including 32, 48, and 60 cells. The safety has been confirmed by TÜV Süd in Germany, who is an independent safety testing service.
TI's presentation lists many advantages to a wireless BMS, and many of these are indeed true. The first main advantage of a wireless BMS is the overall reduction of cables. Fewer cables mean that less can go wrong with physical wiring (such as strain and breakage), and therefore will potentially increase reliability.
The second advantage of a wireless battery management system is simplifying the construction of a vehicle. Traditional cell monitors are wired in series, but the use of dedicated communication cables quickly increases the design's complexity. Thus, the use of a wireless system allows simplifying of the connection system.
According to TI, the third advantage is that the use of a wireless system simplifies the implementation of time-synchronized data. This may be due to the wireless system's ability to read all cell voltages within a few milliseconds.
The fourth advantage of reducing the overall number of wires used is reducing the weight of the vehicle. Electric vehicles are already trying to compete against fossil fuel cars on the range, and every kilogram removed from a vehicle helps improve the overall range. Thus, removing wires reduces the weight, and thereby requires less energy to move the car.
While TI seems to be very positive about a wireless BMS, there are clear warning signs that would make such a system problematic at the least; deadly at the worse.
The first, and most obvious concern, is that wireless systems do not have a direct physical link between the transmitter and receiver. This means that information is more likely to be lost in transit due to noise or external signals interfering.
The second issue arises from the first, safety. If the connection between the BMS and the individual cells is prone to a connection failure, then the system's safety is seriously compromised. Data regarding cell condition, voltage, temperature, and current draw is critical to the battery's safe operation. Thus, using a potentially unreliable communication system means that there may be times when battery health cannot be read.
Thirdly, wireless systems are far easier to hack than a wires system. Cybersecurity is becoming an increasing concern, and it is unlikely that a wireless system can ever be made unbreakable. An attacker who has access to the wireless network could feed in false information and potentially take control of the vehicle. While access to the steering wheel and breaks may not be possible, sending false readings could cause the car to shut down for safety reasons.
Fourthly, TI mentions that the wireless BMS can provide simpler time synchronization of cell data, but this depends on how cell monitors are designed. For each wired cell monitor, time synchronization can be achieved using a synchronized RTC that tracks the current time. Many wireless cell monitors would be needed, and each of these would still need a method for time tracking akin to the wired setup.
The use of a wireless BMS could help improve electric cars, and the advantages described by TI do bring about interesting ideas on car architecture in general. However, wires are tried and tested, and their incredible reliability and resilience to interference make them a safe choice.
Should a battery utilize wireless nodes for gathering cell data? In my opinion, I don’t think so, and I believe that any systems relating to the safety need to utilize cables due to their increased reliability. However, non-safety critical systems could move towards a wireless network that can reduce complexity, reduce the overall weight, and make it easier to upgrade the vehicle in the future.