Quality and performance are key considerations during custom battery pack manufacturing. If these factors are overlooked, potential battery issues and low-performing packs may enter the market. They could cause malfunctions and damage to devices, or not offer enough power for devices to perform.
Engineers perform testing and quality assurance measures on the battery materials, components, battery management systems (BMS), and other features to ensure that the battery is durable, will operate as intended, and will last for a long period of time.
Quality assurance focuses on checking the safety, reliability, and performance of the battery pack. The tests are also used to ensure that the battery pack complies with national and international standards. Customers also want key performance information regarding the battery pack quality and testing as they can use this data in future custom battery pack development. They may also include the information in technical specifications and marketing materials for their end users.
Battery Cell Testing
Battery cell testing is performed throughout the production of the custom battery pack. By doing this testing before configuring it in a pack, problems can be more readily identified and addressed. This benefits both the customer and the engineer by ensuring time deadlines are met, preventing the engineer from having to unnecessarily disassemble the entire battery pack and perform additional testing to search for issues.
Battery pack manufacturers will typically use customized testers for their battery packs. These customized testers may be manual, electronic, or automated. Manual testers are normally used to take measurements of differing loads by discharging the battery. Electronic testers are more customized so that they align with the battery pack that is assessed. The load and the DC source are programmed into the measurement parameters. Automated testers have built-in measurement tools that are combined with electronic tester parts. These testers may be off-the-shelf or customized.
Battery pack being tested during the manufacturing process.
The types of testing performed on cells will check the state of health (SoH), capacity, charging/discharging rates, battery aging, cell balancing, and mechanical stresses. The tests may also check fast charging properties if the battery cell is designed for such factors. Engineers will also use equipment such as thermocouples to take measurements of the temperatures of the battery cells and connected electronics, PAT cells to make electrode measurements, and electrochemical impedance spectroscopy to check the state of charge (SoC) along with the SoH of the batteries.
Engineers do battery cell testing under normal operating conditions as well as during simulated environments. Certain battery cells may be used in harsh environments and conditions. Simulating such circumstances allows the engineer to understand how the battery will function and what issues will arise. This data is relayed to the customer who may wish for design changes to improve performance or include this information with the battery so that the end user is informed of how the battery will perform under certain conditions.
Production Circuit Board Testing
Production circuits are evaluated to ensure the quality assurance of connections and circuitry. The production board helps to protect lithium batteries from short circuits, overcharging, and over-discharging. Printed circuit board (PCB) testing for battery packs is very similar to testing performed for PCBs in electronic devices and other applications.
There are different types of testing options available, including in-circuit testing to check the solder connections, and fly probe testing that checks the resistance, capacitance, opens, shorts, and inductance of the PCB. X-ray inspection to view internal traces, barrels, and solder connections, peel testing to measure laminate strength, solder float testing to how much thermal stress PCB holes can manage, and PCB contamination testing to find Ionic contaminants that could corrode the board or cause other significant issues.
Testing of the circuitry is usually done after the manufacturing of the printed circuit board is completed. When it comes to the hardware and software of the battery management system, engineers perform this testing during battery pack assembly.
Battery Management System Testing
Battery management system testing is vital for lithium-based batteries. This cell chemistry is unstable and requires a BMS to be included with every battery pack under national and international regulations. The hardware of the test is performed to ensure all connections are running optimally. Software testing involves checking that the programmed functions are running based on specifications.
Most BMS have basic safety functions for the battery pack such as checking the SoH, SoC, temperatures, current, voltage, and energy. A customer may also ask that the BMS include additional functions such as cell balancing. Engineers will perform other testing based on the added functions to the BMS. These tests are done by cycling the battery during normal operation and validating the data.
Custom Battery Cycling Tests
Battery cycling is a common test performed throughout the production of the battery pack. Engineers will have the battery undergo a full charge and then a full discharge to check the battery's health, SoC, and internal impedance. BMS testing also relies on cycling to ensure that the software is monitoring the cells accurately under varying conditions. Battery cycling is a necessary procedure that can evaluate the performance of the battery, its product life, how it handles aging, and monitor temperature fluctuations.
End Customer Quality Assurance Measures
Engineers can only guarantee quality assurance during the development and production of the battery pack. Once the battery pack is assembled and tested to meet rigorous standards, it then falls onto the customer to further ensure quality assurance. How the battery is handled, shipped, stored, and used can impact the quality of the battery. Improper storage, transportation, and usage could result in damage, malfunctions, and serious safety concerns.
The battery manufacturer's customer should also understand that any future upgrades to their device could impact the performance and safety of the current custom battery pack. When these changes are made, testing and quality assurance measures should again be performed on the custom battery pack.
Once the battery manufacturer's customer receives and ships out the battery pack by itself or with the device, the end customer of the device can also perform simple quality assurance measures after receiving the device. They should check for cell leakage and loose connections that could impact the performance of the device. They should also take note of extremely high temperatures when charging battery packs, which could indicate a problem. This information can then be relayed back to the company and the manufacturer who can consider it.
Summary
Quality assurance for battery packs is performed throughout the entire life of the cells: from the battery manufacturer to the manufacturer's customer and to the end customer. The collected data at each stage can help further improve the custom battery pack so that it offers optimal performance and long battery life to the applications.
When it comes to testing time and pricing, it will differ based on the battery design and the manufacturer. The customer should speak with the manufacturer to obtain a more precise estimate regarding testing and quality assurance costs.
