Introduction With the advancement of science and technology, electric vehicle technology has developed rapidly. Compared with internal combustion engine vehicles, electric vehicles have advantages such as zero emissions, high performance efficiency, low noise, low heat radiation, easy operation and easy maintenance. They will be the future direction of automobile development and a current research hotspot. There are three types of power batteries for electric vehicles: fuel cells, storage batteries and supercapacitors. Fuel cells, storage batteries and supercapacitors are complementary in terms of energy density and power density [1]. It is difficult to use storage batteries, fuel cells or supercapacitors alone as the power source for electric vehicles. Hybrid batteries are a more ideal solution. Using a hybrid battery drive system, especially utilizing the fast charging and discharging energy of supercapacitors to realize the recovery of vehicle braking energy, and the ultra-high energy density of fuel cells to support the long-term driving of vehicles, makes the hybrid drive system composed of fuel cells/supercapacitors the best solution for electric vehicle drive. For vehicle power supplies, to achieve higher power and energy, supercapacitors are often used in series with multiple individual cells. With the increase in capacitor cascade, the overall battery voltage also increases. For vehicle batteries, the operating voltage of supercapacitors often reaches several hundred volts. Such peak voltage fluctuations cause strong electromagnetic interference, posing significant challenges to the testing of capacitor components. Furthermore, because series-connected supercapacitors often use high-current charging and discharging (typically between 50A and 150A), voltage and current changes are extremely rapid. For example, when a supercapacitor in a medium-sized bus discharges at 150A, the terminal voltage drops from 300V to 70V within one minute, and when charging at a constant voltage of 200V, the current increases from 50A to approximately 150A within a few minutes. This rapid charging and discharging speed and amplitude result in significant noise impact. To address the unique operating conditions of supercapacitors, this paper presents a supercapacitor battery testing system. By conducting charge-discharge cycle tests on supercapacitor components to collect their voltage and current parameters and comparing them with standard parameters, the system verifies that it can quickly achieve high testing accuracy under conditions of strong voltage and current changes. 1. Detection System Principle and Implementation of Each Module 1.1 Detection Object The supercapacitor used for testing adopts two sets of series-connected asymmetric electrode double-layer supercapacitor components provided by Shanghai Aowei Technology Development Co., Ltd. 1.2 System Principle Introduction The supercapacitor management system can realize real-time acquisition of the operating current and voltage of supercapacitors. The overall structure diagram of the supercapacitor management system is shown in Figure 1. The system consists of three main modules: a field voltage and current acquisition and conditioning module (i.e., the acquisition module), a signal isolation and MCU signal processing module (i.e., the central processing module), and a power management module. Within the acquisition module, Hall voltage and Hall current sensors acquire the supercapacitor voltage and current on-site. The acquired signals are amplified and then converted into 4mA-20mA current signals before being sent to the central processing module. Within the central processing module, the 4mA-20mA current signals sent by the acquisition module undergo current-voltage conversion, followed by isolation amplification, AD conversion, and then are sent to the MCU. The MCU processes the data and transmits it to the host computer via the CAN interface. When an abnormal data is detected, the MCU outputs a fault signal so that personnel can take timely measures. The power management module provides stable and isolated voltage for each functional module and adds an RS232 communication serial port for MCU program programming. [IMG=System Principle]/uploadpic/THESIS/2007/12/20071221104545470039.jpg[/IMG] 1.3 Implementation of Major Modules This test system uses four circuit boards to implement three major functional modules: the acquisition module, the central processing module, and the power management module. These are the voltage acquisition and initial conditioning board, the central processing board, and the power supply board. The following focuses on the implementation of the voltage and current acquisition modules and the central processing module. 1.3.1 Implementation of the Acquisition Module The acquisition module includes two parts: bus current acquisition and bus voltage acquisition. Figure 2 shows the current acquisition principle diagram. A Hall current sensor is used to isolate the system under test, which has higher accuracy, better safety performance, and stronger anti-interference ability than the traditional current divider circuit based on resistance sampling. This paper selects the Honywell CSNK591 Hall closed-loop current sensor based on the magnetic compensation principle, with a measurement range of ±1200A, a linear accuracy of 0.1%, an overall accuracy of 0.5%, and a response speed of less than 1μs, fully meeting the system requirements. The acquired signal is converted into a voltage signal by a precision resistor, and then amplified into a ±5V bipolar voltage signal by an instrumentation amplifier. The system uses the AD620BR instrumentation amplifier chip, which has a large common-mode rejection ratio (CMRR) at low gain (minimum CMRR of 100dB at G=10), and can strongly suppress common-mode interference caused by factors such as temperature and electromagnetic noise. The amplified signal is boosted to a 0-10V unipolar signal by an OP27GS chip, and then sent to the XTR110KU transmitter via an emitter follower, where it is converted into a 4mA-20mA current signal and sent to the central processing module. The reason for converting the acquired signal into a 4mA-20mA current signal is to ensure consistency with industrial interface standards and to utilize the strong anti-interference capability of current sensing. The bus voltage acquisition also uses a closed-loop Hall voltage sensor VSM025A based on the magnetic compensation principle, and the implementation principle is the same as that of current acquisition. [IMG=Implementation of Acquisition Module]/uploadpic/THESIS/2007/12/2007122110455337429Q.jpg[/IMG] 1.3.2 Implementation of Central Processing Module The central processing module is the core part of the test system, including MCU and AD units, analog signal secondary conditioning unit, fault output unit, and CAN interface unit, as shown in Figure 3. [IMG=Implementation of Central Processing Module]/uploadpic/THESIS/2007/12/20071221104648720749.jpg[/IMG] The 4mA-20mA current signal input to the acquisition module first passes through the analog signal secondary conditioning unit for signal transmission, isolation, filtering, and amplification. There are many ways to isolate analog signals. Common methods include isolation amplifiers, linear optocouplers, and voltage-to-frequency converters. Among these, isolation amplifiers and linear optocouplers offer high isolation voltage, strong anti-interference capabilities, and high linearity. However, linear optocoupler isolation circuits are complex, requiring adjustment of many parameters, and their linearity is poor when the output voltage is low. Therefore, this paper selects the high-precision ISO124U isolation operational amplifier from Butterworth to isolate the input analog signal. The isolated signal is filtered for high-frequency interference by a 5th-order Butterworth MAX280 low-pass filter circuit, and then sent out through an emitter follower. The acquired signal after secondary conditioning is sent to the MCU via a 12-bit high-speed AD7891. The MCU processes the data and transmits it to the host computer via the CAN interface. The selected microcontroller is the STC89C58RD+, an 8-bit high-speed microcontroller from the STC series. This microcontroller features strong anti-interference capabilities, including 4kV Fast Impulse Interference (EFT) and high electrostatic discharge (ESD) immunity, capable of withstanding 6000V ESD. This effectively meets the high-voltage, high-current operating environment of supercapacitors. The microcontroller can operate in six clock modes. In this system, using a 24MHz crystal oscillator, the microcontroller's operating frequency reaches 4MIPS, equivalent to four times the operating speed of a typical 51-series microcontroller. Furthermore, the test system includes three fault diagnosis outputs, capable of displaying undervoltage, overvoltage, and overcurrent conditions. The test system communicates with the host computer using a robust and stable CAN communication method, ensuring the reliability of data transmitted from the test system to the host computer. The actual system requires analog ±15V, digital ±5V, and analog ±12V power supplies. The power management module provides the necessary voltages to each part of the system while isolating analog and digital circuits to prevent mutual interference. TVS protection is added to each power input to prevent damage from surge voltages. Corresponding filtering circuits are also installed at many power inputs, such as a π-shaped filter circuit at the AD power input, effectively eliminating interference from power signals. Furthermore, all external connections use shielded cables, effectively shielding against electromagnetic interference during transmission. All current boards are packaged in aluminum profile boxes and connected to external circuits using standard aviation connectors, thus protecting the circuit boards while isolating them from external magnetic fields. 2. Test System Measured Results Comparison and Analysis 2.1 Test Content The experiment selected 70A and 150A modes to conduct charge and discharge tests on two sets of series-connected supercapacitor components. First, the capacitors were charged with a constant current. When the bus voltage reached 300V, constant voltage charging was switched to. When the bus current dropped to 10A, a 70A constant current discharge was performed. This cycle was repeated for 5 periods. 2.2 Experimental Results and Analysis Figures 4 and 5 show the comparison of test curves under two conditions. Figure 4 represents the current variation curves under the two standard test conditions of 70A and 150A. Figures 4 and 5 show the voltage curve characteristics under the two conditions. It can be seen that the matching degree between the two is very good, and the voltage test accuracy is higher than the current test accuracy. This is because, on the one hand, the voltage of the charging and discharging system itself has higher control accuracy than the current. On the other hand, the current sensor is placed in the capacitor box and relies on only a single capacitor. The noise interference generated during capacitor charging and discharging is relatively serious. At the same time, the Hall current sensor has a large aperture, and there is still a certain gap after passing through the current bus, which affects the test accuracy to a certain extent. Comparing the current curves of each group, it can be seen that as the current increases, the relative error of the test results decreases, but the absolute error remains consistent and does not exceed 3A. [IMG=70A Voltage Curve Characteristics]/uploadpic/THESIS/2007/12/2007122110542553884P.jpg[/IMG] [IMG=150A Voltage Curve Characteristics]/uploadpic/THESIS/2007/12/2007122110543355806H.jpg[/IMG] Conclusion This paper presents an on-board supercapacitor testing system. The system uses Hall effect closed-loop current and voltage sensors based on magnetic compensation principles to acquire bus signals. Signal processing is performed by a high-speed STC51 microcontroller resistant to high-voltage pulse interference. Instrument amplification, current transmission, analog signal isolation, and 5th-order low-pass filtering are employed to minimize noise during signal transmission. Charge-discharge tests on supercapacitor components demonstrate that the system has strong anti-interference capabilities and high detection accuracy, effectively meeting the testing requirements of on-board supercapacitors under high-voltage and high-current environments.