Application Cases

Experiment Name: Battery Heating and Charging Experiment

Significance of the Experiment: With the rapid development of the economy and society, the demand for energy is increasing daily, especially in the transportation sector. Against the backdrop of the depletion of fossil fuels and environmental pollution, new energy vehicles have a broad development prospect. In recent years, new energy vehicles, mainly pure electric vehicles, have developed rapidly and are expected to replace traditional internal combustion engine vehicles. The performance of lithium-ion batteries directly affects the range, safety, and reliability of electric vehicles. In low-temperature environments, lithium-ion batteries experience deteriorated power characteristics, reduced cycle life, and decreased available capacity. They also face difficulties in low-temperature charging and the risk of lithium plating during charging, which hinders the development of electric vehicles. Low-temperature heating technology is one of the core technologies of battery thermal management systems and is key to alleviating the performance degradation of power batteries in low-temperature environments.

Experiment Principle: This experiment is based on the AC heating method for battery heating and charging tests. The AC heating method generates heat by applying an AC current to the battery, heating it from the inside. It also superimposes a DC component on the AC signal to charge the battery while heating. The AC heating method uses an external AC power source, so the heating process does not consume the battery's own energy. Among various AC waveforms, sinusoidal AC is the most widely used. This experiment uses the Aigtek ATS-M1010C current transformer as the drive power source. The experimental block diagram and the physical diagram of the experiment are shown in Figures 1 and 2, respectively.

Figure 1: Experimental Flowchart

Figure 2: Experimental Setup

Testing Equipment: Signal generator, ATS-M1010C current transformer, oscilloscope, rechargeable lithium battery, infrared thermometer, multimeter

Experiment Process: The signal generator provides an AC signal to the ATS-M1010C current transformer. First, the AC and DC bias are pre-set when the instrument is unloaded. The charging current for the lithium battery used in this experiment is 1-2A. The parameters set on the signal generator are 10kHz, 812mVpp, +100mV (Offset). The current waveform is observed using the oscilloscope connected to the current detection port of the current transformer. The pre-set current waveform is shown in Figure 3. After the signal is pre-set, a partially charged lithium battery is used for testing. Before applying power, the battery's temperature and voltage are tested using an infrared thermometer and a multimeter, respectively. The initial temperature and voltage are 16.4℃ and 0.264V, as shown in Figures 4 and 5, respectively. Next, the power application test is conducted for five minutes.

Figure 3: No-load Waveform

Experimental Results: After five minutes of power application, the results are shown in Figures 6 and 7. The battery's temperature and voltage are 30.1℃ and 3.107V, respectively. The results indicate that the battery is significantly heated after a period of AC signal application, and the superimposed DC bias successfully charges the battery, achieving simultaneous heating and charging. Additionally, changing the amplitude and frequency of the AC current will affect the internal heat generation power of the battery, thereby affecting the heating rate. It is important to note that the DC component is the charging current of the battery. When investigating the effects of AC signal frequency and amplitude on heating rate, it should remain constant. The experimental results show that within a certain range, higher current amplitude, lower current frequency, and good insulation conditions are conducive to increasing the battery heating rate. The optimized heating method measured can heat the battery from 16.4℃ to 30.1℃ in just 5 minutes, with a heating rate of 2.74℃/min. The temperature rise chart is shown in Figure 8.

Figure 8: Battery Temperature Rise Chart

For electric vehicle applications, research on low-temperature AC heating is still in its infancy. How to efficiently and safely heat batteries in low-temperature environments remains a challenge. To accelerate the engineering application progress of internal heating methods and composite heating methods, several issues need to be addressed:

1. Existing research on heating strategies has insufficient studies on battery aging, and the impact of current parameters on battery life at the electrochemical mechanism level needs further investigation. Future research should establish electrochemical models of batteries to reveal the effects of current parameters on battery aging from a mechanistic perspective, clarify the range of current parameters under which batteries do not age under different operating conditions, and further improve heating efficiency and safety.

2. Most existing heating method studies focus on individual batteries, with insufficient research on battery modules and packs. Temperature uniformity within the module will significantly affect the performance and aging rate of the battery pack. Battery heat generation models and thermal models are the theoretical basis for the design of low-temperature thermal management systems. Future research should further study accurate and efficient electro-thermal coupling models from the levels of individual batteries, battery modules, and battery packs, considering the impact of battery inconsistency, to improve the accuracy and speed of temperature prediction and provide theoretical support for system optimization design and heating control strategy design.