High-precision robust monitoring of charge/discharge current over a wide dynamic range for electric vehicle batteries using diamond quantum sensors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-09-06 |
| Journal | Scientific Reports |
| Authors | Yuji Hatano, Jae-Won Shin, Junya Tanigawa, Yuta Shigenobu, Akimichi Nakazono |
| Institutions | Yazaki (Japan), National Institutes for Quantum Science and Technology |
| Citations | 59 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond Quantum Sensors for EV Current Monitoring
Section titled âTechnical Documentation & Analysis: Diamond Quantum Sensors for EV Current MonitoringâThis document analyzes the research paper âHigh-precision robust monitoring of charge/discharge current over a wide dynamic range for electric vehicle batteries using diamond quantum sensorsâ and outlines how 6CCVDâs advanced MPCVD diamond capabilities can support and extend this critical research area.
Executive Summary
Section titled âExecutive SummaryâThis study successfully demonstrates a robust, high-precision current sensor utilizing Nitrogen-Vacancy (NV) centers in Single Crystal Diamond (SCD) for Electric Vehicle (EV) battery monitoring.
- Core Achievement: Developed a diamond quantum sensor capable of achieving 10 mA current detection accuracy, resolving a major limitation in EV State of Charge (SoC) estimation.
- Dynamic Range & Robustness: Confirmed operation over a wide dynamic range of ± 1000 A and across the full automotive temperature range (-40 °C to +85 °C).
- Noise Mitigation: Implemented differential detection using two SCD sensors to effectively eliminate common-mode environmental magnetic noise and excitation light noise.
- Material Specification: The sensor utilized 2 x 2 x 1 mm³ Ib (111) SCD crystals, electron-irradiated (3 x 1018 cm-2) and annealed (1000 °C) to achieve 5-6 ppm NV concentration.
- System Control: Employed a mixed analog-digital control system to trace the magnetic resonance frequency over a 1 GHz range, ensuring stability and linearity across the wide current range.
- Commercial Impact: The 10 mA accuracy enables 0.1% SoC estimation, potentially eliminating the standard 10% SoC margin and stretching EV driving range by 10%.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper detailing the performance and material requirements of the diamond quantum sensor system.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Current Detection Accuracy (Target/Achieved) | 10 | mA | Required for 0.1% SoC estimation |
| Maximum Current Dynamic Range | ± 1000 | A | Confirmed operational limit |
| Operating Temperature Range | -40 to +85 | °C | Full automotive standard |
| Linearity (High Current Range) | ± 0.3 | % | Measured from 40 A to 1000 A |
| Linearity (WLTC Range) | ± 0.5 | % | Measured from 1 A to 130 A |
| Current Fluctuation Noise Floor | 10 | mA/Hz0.5 | Theoretical accuracy over full range |
| Sensor Material Type | Ib (111) | N/A | Single Crystal Diamond (SCD) |
| Sensor Dimensions | 2 x 2 x 1 | mmÂł | Custom cut crystal size |
| NV Concentration (Estimated) | 5-6 | ppm | Result of irradiation and annealing |
| Static Magnetic Field (B0) | 19 | mT | Provided by Neodymium magnet |
| Resonance Frequency Difference (RFD) | 1050 | MHz | RH - RL without busbar current |
| Busbar Thickness | 8 | mm | Copper, used to suppress heating |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise material engineering and advanced differential detection techniques to achieve high sensitivity in a noisy environment.
- SCD Preparation: Ib (111) Single Crystal Diamond (SCD) plates (2 x 2 x 1 mmÂł) were selected as the base material.
- NV Center Creation: The SCD crystals were subjected to electron irradiation (3 x 1018 cm-2) and subsequently annealed at 1000 °C to form the Nitrogen-Vacancy (NV) centers (estimated 5-6 ppm concentration).
- Sensor Head Fabrication: Two diamond sensors (A and B) were adhered to multimode optical fibers (400 ”m core diameter, NA 0.5).
- Differential Placement: Sensors A and B were fixed on opposite sides of an 8 mm thick copper busbar, 5 mm from the busbar surface, to measure the magnetic field differentially.
- Static Field Application: A 19 mT static magnetic field was applied parallel to the [111] NV axis using Neodymium magnets to enable Optically Detected Magnetic Resonance (ODMR).
- Noise Cancellation: Differential detection (LOD = Y - X) was used to eliminate common-mode noise, reducing external magnetic field noise by one order of magnitude and excitation light noise by half.
- Wide Dynamic Range Control: A mixed analog-digital control system was implemented to adjust the microwave generator frequency, allowing the system to trace the resonance frequency over the full 1 GHz range required for ± 1000 A measurement.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of this high-precision EV current sensor hinges on the quality and customization of the diamond material. 6CCVD is uniquely positioned to supply the necessary components and engineering support to replicate, scale, and advance this technology.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, high-quality, low-strain SCD is essential for achieving long NV coherence times and high sensitivity.
- Optical Grade SCD (Single Crystal Diamond): 6CCVD specializes in high-purity, low-birefringence SCD wafers, providing the ideal precursor material for NV center creation via irradiation and annealing. Our SCD material ensures the wide band gap and thermal stability necessary for -40 °C to +85 °C operation.
- Substrate Thickness: We offer SCD substrates ranging from 0.1 ”m up to 500 ”m, and robust substrates up to 10 mm thick, suitable for high-dose electron irradiation and subsequent high-temperature annealing (1000 °C).
Customization Potential
Section titled âCustomization PotentialâThe paper utilized specific 2 x 2 x 1 mmÂł sensor geometries and required precise integration with microwave components. 6CCVD offers comprehensive customization services to meet these needs.
| Requirement from Paper | 6CCVD Customization Service | Benefit to Client |
|---|---|---|
| Specific Dimensions (2x2x1 mmÂł) | Precision Laser Cutting: We provide custom shaping and laser cutting services to achieve exact, repeatable sensor geometries from larger wafers. | Ensures rapid prototyping and high-volume production of standardized sensor heads for automotive integration. |
| Microwave Antenna Integration | In-House Metalization: We offer internal deposition of critical metals (Au, Pt, Pd, Ti, W, Cu) for creating integrated microwave antennas or bonding pads directly onto the diamond surface. | Streamlines the supply chain for complex sensor heads requiring integrated electronic structures. |
| Surface Finish (Optical Quality) | Ultra-Low Roughness Polishing: Our SCD polishing achieves Ra < 1 nm, maximizing light collection efficiency and minimizing scattering losses for ODMR signal detection. | Improves the signal-to-noise ratio, directly contributing to the required 10 mA accuracy. |
Engineering Support
Section titled âEngineering SupportâThe development of diamond quantum sensors for automotive applications requires expertise in both material science and quantum physics.
- NV Center Optimization: 6CCVDâs in-house PhD team can assist researchers and engineers in selecting the optimal SCD crystal orientation (e.g., (111) as used here) and material purity to maximize NV yield and coherence time for similar EV Current Monitoring projects.
- Thermal Management Consultation: We provide guidance on selecting appropriate diamond material specifications (e.g., thickness, thermal grade) to ensure robust performance and heat dissipation in high-current, high-temperature environments.
- Global Supply Chain: We offer reliable global shipping (DDU default, DDP available) to ensure timely delivery of custom diamond components worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Accurate prediction of the remaining driving range of electric vehicles is difficult because the state-of-the-art sensors for measuring battery current are not accurate enough to estimate the state of charge. This is because the battery current of EVs can reach a maximum of several hundred amperes while the average current is only approximately 10 A, and ordinary sensors do not have an accuracy of several tens of milliamperes while maintaining a dynamic range of several hundred amperes. Therefore, the state of charge has to be estimated with an ambiguity of approximately 10%, which makes the battery usage inefficient. This study resolves this limitation by developing a diamond quantum sensor with an inherently wide dynamic range and high sensitivity for measuring the battery current. The design uses the differential detection of two sensors to eliminate in-vehicle common-mode environmental noise, and a mixed analog-digital control to trace the magnetic resonance microwave frequencies of the quantum sensor without deviation over a wide dynamic range. The prototype battery monitor was fabricated and tested. The battery module current was measured up to 130 A covering WLTC driving pattern, and the accuracy of the current sensor to estimate battery state of charge was analyzed to be 10 mA, which will lead to 0.2% CO 2 reduction emitted in the 2030 WW transportation field. Moreover, an operating temperature range of â 40 to + 85 °C and a maximum current dynamic range of ± 1000 A were confirmed.