Optimizing battery testing performance

The future of battery testing is likely to focus on faster, more efficient methods capable of rapid assessments during operation. This type of assessment will be increasingly valuable as batteries become more integrated into critical industrial applications. While electrochemical impedance spectroscopy is a powerful research tool, its cost and difficulty of use limit its potential. More accessible, streamlined versions of this technology will shape the future of the battery testing industry.

An essential component of everyday life

Few devices impact our lives as much as batteries. In everyday household appliances, batteries power essentials such as remote controls, smartphones, radios and clocks. Industrial applications for batteries play an even more critical role, as they power everything from hybrid vehicles to telecommunications systems, even satellites and space missions. Whether someone is restarting a heart with an automatic external defibrillator or simply driving to work in an electric vehicle (EV), batteries power our lives. Battery testing is becoming more crucial as the importance of batteries in our daily lives increases.

Types of commercial battery testing

There are three primary types of battery testing: performance, health, and specialized.

Performance testing examines the battery’s electrical performance under various conditions. Researchers may test the battery in extreme temperatures, at maximum or minimum load capacity, and evaluate its performance during charge and discharge cycles¹. Capacity testing determines how long a battery can hold a charge, while load testing measures its ability to deliver a current. Discharge testing measures the rate at which a battery loses voltage.

Batteries also undergo health testing to measure internal resistance, electrolyte levels, and the rate at which the battery drains when not in use (self-discharge). A high level of internal resistance can indicate a battery is nearing the end of its life. Resistance measurements can vary widely between lead-acid batteries, so the resistance method is most effective when comparing readings of a given battery from creation through retirement². Modern lead-acid and lithium-ion batteries maintain a continual level of resistance that is not indicative of their capacity.

Internal resistance testing helps identify potential corrosion or damage. There are several ways to measure internal resistance, but the most relevant in a laboratory setting is electrochemical impedance spectroscopy (EIS). This type of testing requires expert equipment and is labor intensive, which keeps it predominantly in the domain of research scientists². EIS allows researchers to characterize the behavior of a battery at different States of Charge (SoC). It is a key technique for characterizing electrochemical reaction mechanisms and optimizing battery materials³.

Electrolyte levels are crucial to proper battery function. Depending on the type of battery, the electrolyte solution can be a liquid or similar to a paste that transports positively charged ions between the cathode and anode terminals. Some modern batteries use solid ceramic electrolytes, such as lithium metal oxides, to eliminate the risk of leaking and flammability⁴. Testing electrolytes may require a hydrometer. Otherwise, a visual inspection will indicate if more electrolyte fluid is required. Many modern batteries rely on a battery management system (BMS) to detect electrolyte deficiencies or unsafe conditions. Most BMS will shut down the battery if a safety concern is detected.

Lithium-ion batteries can lose charge over time even when nothing is drawing power. This phenomenon is called self-discharge or leakage. Engineers designing lithium-ion battery-powered devices must predict the expected leakage rate and relay that information to the end consumer. In an EV, for instance, the driver would want to know their maximum range (with the self-discharge rate taken into account). Testing for leakage requires the battery to be tested with a voltmeter while fully charged. Time is allowed to elapse, then the battery is tested again to measure the amount of SoC change.

There are also several types of specialized testing, depending on the battery type and application. These include thermal testing, vibration testing, and safety testing.

Thermal testing allows engineers to assess a battery's performance in extreme temperatures. Vibration testing evaluates a battery’s durability under stress. Most importantly, safety testing ensures the battery meets safety regulations.

Benefits of battery testing

Regular testing can aid in preventative maintenance and ensuring batteries function properly throughout their lifecycle. Performing preventative maintenance also extends the battery’s life and reduces downtime.

A key reason to perform battery testing regularly is safety. While many industrial batteries have a built-in BMS, damaged batteries still pose a risk of fire, toxic vapor off-gassing, or even explosions⁵.

Commercial-grade battery testing equipment

Battery testing equipment ranges from basic to specialized. Basic equipment includes battery resistance testers, digital hydrometers, as well as lead acid battery chargers, dischargers, and activators. Impedance and capacity testers are also valuable tools for a battery testing arsenal. Engineers and manufacturers may use specialized equipment like battery test chambers to test their products in a safe, controlled environment.

How to choose a battery testing solution

When deciding on a testing solution, consider the type and size of the battery. What capabilities do you need your testing equipment to have? Equipment can range significantly in price, so consider and define your budget as early as possible. Examine the equipment for ease of use by reading product reviews from your peers to determine how well an item is designed and if advanced training is necessary for operation.

Further reading and resources:

• The future of energy storage: Improving lithium-ion batteries and exploring alternatives
• Application Note: Temperature simulation for quality assessment of batteries
• The importance of thermal management in optimizing battery performance

References:

1. Associated Environmental Systems. The Importance of Battery Testing. (2023, May 19). https://www.associatedenvironmentalsystems.com/blog/the-importance-of-battery-testing. Accessed June 1, 2024.

2. Battery University. BU-902: How to Measure Internal Resistance. (2021, November 4). https://batteryuniversity.com/article/bu-902-how-to-measure-internal-resistance. Accessed June 2, 2024.

3. BioLogic. What is Electrochemical Impedance Spectroscopy (EIS)? (2023, September 7). https://www.biologic.net/topics/what-is-eis/. Accessed June 3, 2024.

4. Dragonfly Energy. What is Battery Electrolyte and How Does It Work? (2022, December 14). https://dragonflyenergy.com/battery-electrolyte/. Accessed June 3, 2024.

5. ReadyNC. Lithium-Ion Battery Safety. https://www.readync.gov/plan-and-prepare/protect-your-home/lithium-ion-battery-safety. Accessed June 3, 2024.