The Inside Story on a Solution for Evaluating 300A~4800A High-Power Battery Performance

In a bid to develop electric vehicles (EVs) that offer both safety and high performance, battery researchers are dedicated to improving the energy density, cycle life, and safety of automotive battery cells. To ensure these development efforts comply with regulations and performance standards, engineers must rely on professional and efficient equipment to perform a range of rigorous battery tests.

Q1. Important ways of verifying the performance of automotive battery cells include fixed-load and high-speed dynamic load evaluation. What aspects should users take into account when choosing the appropriate equipment for such high-current tests?

A1. With the development of fast charging and racing modes for electric vehicles, the battery cells require a higher current capability. Coupled with the increased capacity of individual battery cells, test currents can reach several hundreds or even thousands of amperes. If your equipment specification is defined based on the peak testing current, you’re looking at much higher equipment prices. However, as the high-rate current mode tests involve short-duration high-current pulses, by purchasing test equipment capable of outputting such pulses you can significantly reduce your equipment procurement costs.

Q2. What benefits does energy recovery (regenerative) design in battery cell charge-discharge equipment offer in terms of battery cell testing?

A2. To be sure, the conversion efficiency of energy recovery in battery cell charge-discharge equipment is not as high as that of battery packs due to the low operating voltage of battery cells. However, battery cell testing involves numerous test items and long verification cycles, often requiring a large number of channels to perform validation of battery products. Over time, a significant amount of the energy discharged during this process can be recovered. The energy recovery design not only saves long-term operational costs but also reduces the costs associated with facility power distribution and air conditioning. Furthermore, the high power density of energy recovery-based charge-discharge equipment can reduce the overall equipment footprint and lower carbon emissions, helping manufacturers achieve efficient and sustainable production.

Q3. What conditions should the charge-discharge test equipment meet when used for evaluating the performance of automotive batteries and ensuring compliance with the test requirements of international vehicle manufacturers?

A3. The evaluation of automotive battery cells focuses on dynamic performance testing, such as the Hybrid Pulse Power Characteristic (HPPC) test defined by USABC, the dynamic stress test according to IEC 62660, etc. Test equipment with short current response time and charge-discharge switching time is preferable. The faster the response speed, the higher the output fidelity. There should not be any significant current overshoot, as this can cause transient over-potential and result in varying degrees of damage to the battery, affecting the final experimental results. In addition, crossover delay between charge and discharge transitions should be avoided, as the crossover time directly affects waveform distortion. In terms of measurement, a fast sampling rate reduces errors in the calculation of dynamic capacity, while a shorter data recording cycle can better capture the dynamically changing characteristics, improving the accuracy of internal resistance and power calculations. The accuracy of voltage/current measurement should be as high as possible, but attention should also be paid to the specifications for accuracy and data smoothing cycles. While smoothing enhances precision, it can distort dynamic measurements, so it should be consistent with the minimum recording cycle. Additionally, high-current test equipment should have multiple current ranges to reduce errors in low-current measurements.

Q4. Are there any other key points to consider with respect to testing automotive battery cells?

A4. Safety testing should incorporate the appropriate safety mechanisms based on the EUCAR Hazard Level defined for the product development stage of the battery cells. The equipment should also have abnormal data detection capabilities to identify any anomalies and prevent further testing of faulty cells. The test equipment itself should also have a multi-layer protection mechanism to ensure safety even in the event of a single circuit failure. Additionally, it is important to integrate external safety mechanisms such as fire suppression systems and safety chambers equipped with smoke, gas, and temperature detection capabilities. These external safety measures, along with appropriate protective action mechanisms based on safety engineering design, help minimize potential damage.

Q5. What value does CHROMA’s new product bring to users?

A5. Chroma's new charge-discharge testing system, the 17010H, has been developed specifically for high-current performance testing applications above 300A. As traditional non-regenerative charge-discharge test equipment consumes a significant amount of energy and generates substantial waste heat in this range, it is bound to be phased out due to global decarbonization trends. Still, non-regenerative equipment does offer some advantages, such as rapid current response and high accuracy. The Chroma R&D team has been hard at work to design regenerative circuitry that achieves performance comparable to non-regenerative systems. We are proud to announce that the result is a high-performance and superbly efficient solution for high-current testing of automotive battery cells. Two technological advancements are especially notable: (1) the Super Mode function and (2) a 10% increase in energy conversion efficiency.