High-precision electric vehicle battery monitoring with quantum diamond sensors for range extension

Credit: Tokyo Tech

The popularity of electric vehicles (EVs) as an environmentally friendly alternative to conventional gasoline vehicles is on the rise. This has led to research efforts directed towards the development of high-efficiency EV batteries. But a major inefficiency of electric vehicles results from inaccurate estimates of battery charge. The state of charge of an EV battery is measured based on the current output of the battery. This provides an estimate of the vehicles remaining range.

Typically, battery currents in electric vehicles can reach hundreds of amperes. However, commercial sensors that can detect such currents cannot measure small changes in current at milliamp levels. This leads to an ambiguity of around 10% in the battery charge estimate. This means that the range of electric vehicles could be extended by 10%. This, in turn, would reduce inefficient battery usage.

Now a team of Japanese researchers, led by Professor Mutsuko Hatano of the Tokyo Institute of Technology (Tokyo Tech), have found a solution. In their study published in Scientific reportsthe team reported a detection technique based on a diamond quantum sensor that can estimate battery charge with 1% accuracy while measuring the high currents typical of electric vehicles.

“We have developed diamond sensors sensitive to milliampere currents and compact enough to be implemented in automobiles. In addition, we have measured currents in a wide range as well as milliampere level currents detected in a noisy environment”, explains the professor Hatano.

In their work, the team made a sensor prototype using two quantum diamond sensors that were placed on either side of the busbar (electrical junction for incoming and outgoing currents) in the car. They then used a technique called “differential sensing” to eliminate the common noise detected by the two sensors and keep only the real signal. This, in turn, allowed them to detect a small current of 10 mA amid background ambient noise.

Next, the team used mixed analog-digital control of the frequencies generated by two microwave generators to plot the magnetic resonance frequencies of the quantum sensor over a bandwidth of 1 gigahertz. This enabled a wide dynamic range (ratio of largest to smallest sensed current) of ±1000 A. Additionally, a wide operating temperature range of -40 to +85°C was confirmed to cover general vehicular applications .

Finally, the team tested this prototype for WLTC (Worldwide Harmonized Light Vehicles Test Cycle) driving, a standard test for the energy consumption of electric vehicles. The sensor accurately plotted charge/discharge current from -50A to 130A and demonstrated the accuracy of battery charge estimation within 1%.

What are the implications of these findings? Professor Hatano said: “Increasing battery utilization efficiency by 10% would reduce battery weight by 10%, which would reduce operating energy by 3.5% and energy 5% production of 20 million new electric vehicles in WW 2030. This in turn corresponds to a 0.2% reduction in CO2 WW 2030 transport emissions.”

Measuring currents in the heart at millimeter resolution with a diamond quantum sensor

More information:
Robust, high-accuracy charge/discharge current monitoring over a wide dynamic range for electric vehicle batteries using quantum diamond sensors, Scientific reports (2022). DOI: 10.1038/s41598-022-18106-x

Provided by Tokyo Institute of Technology

Quote: High Precision Electric Vehicle Battery Monitoring with Quantum Diamond Sensors for Range Extension (September 6, 2022) Retrieved September 10, 2022 from https://techxplore.com/news/2022-09-high -accuracy-electric-vehicle-battery-diamond.html

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