Battery Life Cycle Testing

In the first quarter of 21^st century, energy storage devices, including batteries, have become more important than ever. This is because of increased emphasize on renewables, EVs, and other sustainable practices. Enhanced use of batteries has made battery service life considerations more relevant as it relates to durability, costs, and performance.

To test and predict different performance parameters of batteries and battery packs, appropriate tests are developed and standardized. Battery life cycle testing is carried out to give an estimate of charge/discharge cycles, a battery can withstand, before its performance degrades significantly. Life cycle tests are performed to validate design, improve design, enhance client’s confidence in product, and make battery based systems more efficient, cost-effective, and safe.

What is Battery Life Cycle Testing?

Battery life cycle testing is also known as charge-discharge cycling, aging test, or cycle life testing. Usually, lab tests are performed to measure cycle life, but real-world usage can also be monitored to fulfil this purpose. In labs, accelerated aging process is performed by rapidly charging and discharging a battery and monitoring how performance parameters of that battery are affected after each cycle. When performance degrades and goes below a specific limit, testing is considered to be completed. Here are some important factors regarding battery’s life cycle testing

• Life cycle testing is a quite complex process because life cycle is not a static number, rather it is a dynamic metric which is influenced by several factors. These factors include depth of discharge (DoD), C-rates (charge and discharge rates), battery type, electrolyte’s quality and quantity, heat dissipation, environmental conditions, and so on.
• Various performance parameters are monitored and analyzed during aging tests. Voltage, current, internal resistance, and capacity are notable characteristics which denote overall battery’s state of health (SoH) and help determine life cycles.
• Capacity is considered as most important performance parameter for this test. Number of charge-discharge cycles performed on battery before capacity drops to 80% (or target capacity) of its originally rated capacity correspond to cycle life.
• Charging and discharging for cycle life testing can be performed in a way that would resemble real-life usage. It means charge and discharge rates can be changed, temperature can be controlled, mechanical factors can be set, depth of discharge can be limited and so on.

Main Factors Affecting Battery Life Cycle:

There are many internal and external factors that affect life cycle of battery. Understanding of these factors can help you understand your battery better and use it in appropriate manner to prolong its life cycle.

Internal factors belong to size and design of battery in one or the other way. Composition and chemistry of electrolyte, separator, and electrodes affect internal resistance and battery’s life cycle. Size, shape, and weight also impact resistance, heat dissipation, and safety. SOH (State of health) and SOC (State of Charge) also keep changing and affecting life cycle.

Externally, humidity and environmental temperature are most notable parameters. Attached load and source supply affect DoD (Depth of Discharge) and charging rate impacting life cycle of battery.

Choosing Equipment for Battery Life Cycle Testing:  

Researchers and industrialists have developed numerous devices and systems to test various types of batteries. These systems might test multiple performance parameters or one particular parameter. Devices, which are used to conduct battery tests to estimate life cycles specifically, are referred to as battery cyclers. While choosing equipment for battery’s life cycle tests, you must consider size, type, and specifications of your battery. Moreover, your testing goals are of prime importance. Specifications of your selected battery cycler must be capable of serving your goals regarding accuracy, precision, sampling rate, data analysis, safety features etc.

These key performance and selection parameters are discussed here briefly to help you choose right equipment for your battery’s life cycle testing.

For battery life cycle test, testing procedures is repeated over and over again; monitored data is stored, sorted, and analyzed; and data is exchanged between various components and accessories. This indicates that chosen equipment shall have communication interfaces, and data logging features. Your chosen equipment shall be able to support realistic test protocols so it could simulate expected or actual use conditions of your battery or batteries (connected in series or parallel).

For various applications; voltage, current, power, and energy requirements are different. These parameters correspond to battery size. Indirectly, battery size and specifications are chosen as per application requirements. While choosing battery cycler, you must keep your battery size and ratings in mind and make sure that battery cyclers shall also have ratings matching with that of battery. Testing tool with right size is necessary for optimized efficiency, time-saving, and accurate results.

Aging test is always time consuming so, considering your goals and number of batteries for experimentation, you can choose such battery cycler which will have multiple independent channels that could perform tests on multiple batteries at once.

Electrochemical impedance spectroscopy (EIS) helps analyze impedance data that might be changing with battery cycling. This is frequency dependent feature and many manufacturers are incorporating EIS capability into their life cycle testing equipment even for multi-channel testers that can be shared among all channels.

To add further, one cycler might have been designed for just one type of battery. You could choose a cycler that might have different channels to support different types of batteries.

If you are looking for battery life cycle testing equipment for advanced analysis or R&D purpose, then accuracy, precision, and resolution also become important consideration factors.

Battery cyclers also encompass software. This is used majorly to log and analyze data. So, one can prefer that cycler which would contain temperature logging, analyzing tools, and graphs or other presentation forms. Temperature logging is highly important recordable parameter because thermal runaways can destroy battery and even if thermal runaway doesn’t happen, battery’s cycle life gets impacted.

In electric systems, current, voltage, and time are core parameters that are sampled, monitored, and analyzed. According to need, other parameters are calculated using these core parameters. These values can be calculated using software or hardware. Readings and thus data is lost between hardware and software systems because of sampling rate. It indicates that calculations made directly by hardware system will be more precise. So you can choose those battery life cycle testing equipment that would have hardware embedded for the purpose.

Accessories available with equipment, safety features, embedded software, and after-sales support also enhance testing experience. While choosing life cycle battery tester, you must consider hardware and software features. User-friendliness of software and support available to commission, install, and use product is always important.

Methodologies for Battery’s Life Cycle Testing

Each battery cycler or battery life cycle testing equipment is designed to test specific type of battery while following a well-defined testing method. For example, for rechargeable lithium ion battery, charge/discharge cycling can be done in the following way:

First, battery under consideration is discharged keeping the discharge rate 1.2C to 1.4C, discharging is performed until cut-off discharging voltage of 3.3V to 3.55V is achieved. Afterwards, Charging is performed with pre-defined C-rate after a pause. This charge-discharge cycle is repeated again and again until capacity of battery is reduced to 80% of its initial original capacity. Number of charge/discharge cycles performed until this benchmark give battery’s life cycles. During testing, temperature cycling test can also be performed. To do so, battery is placed in a thermal chamber and temperature is raised and lowered according to real-time situation.

As test is run with or without thermal chamber, all electric parameters (current, voltage, and resistance against time) are sampled and recorded. Here, a software system can be used that would automate the testing procedure i.e. testing conditions will be set automatically and results will be recorded. Afterwards, power, charge, capacity, and other parameters of interest are calculated. Again, it would be good if your software would be capable of making calculations for each sample point. Once, one cycle is run and all values are available, data can be sorted and presented for analysis.

For battery life cycle assessment, IEC62660-1 outlines testing procedure in detail and testing requirements for lithium ion battery cells. This standard also details power tests and current voltage characteristic test for the purpose.

Best Battery Life Cycle Testing Equipment in Market

If you are looking for a battery life cycle testing equipment, you shall know your battery and its operating environment in detail. Moreover, you shall be clear about your budget, goal, timeline etc. Here some of the top manufacturers and suppliers for battery cyclers are named to help you select appropriate one based on your needs.

Sinexcel-RE:

Sinexcel-RE has proven itself leader in providing highly precise battery test solutions. Its systems come with advanced software and hardware technology which are suitable for EV manufacturers, universities, research labs, and battery manufacturers worldwide. All of its battery testing products are reliable and embed various safety features. Its software doesn’t perform data analysis only, but also controls testing conditions.

Su-vastika:

SU-vastika manufactures advanced level battery testers which offer various testing modes depending upon testing requirements. Its systems have user friendly interface and are compatible with different types of lithium batteries. Su-vastika’s battery cyclers also incorporate various safety features and provide results after each cycle.

ACEY:

XIAMEN ACEY INTELLIGENT EQUIPMENT CO., LTD is known for its quality battery testing equipment. ACEY designs and delivers battery cyclers that can be used for different types of batteries including lithium ion battery, nickel cadmium battery, and lead acid battery. It also gives its client option for customized solutions for battery testing.

STInstruments:

STinstruments keeps designing and introducing new battery cyclers into the market. Its latest BioLogic-9xx ‘plug and play’ series is suitable for academic research, quality control, and industrial development purpose. Products of this series are equipped with Electrochemical Impedance Spectroscopy (EIS) feature also.

FAQs

1. Are there any challenges associated with battery life cycle testing?

While benefits of life cycle testing are clear that it helps battery manufacturers and researchers improve design, performance, and quality of their battery systems but, sometimes, challenges associated with these tests are not clear. Anyhow, you can expect spending lot of time and money for running these tests. Furthermore, these tests pose safety concerns inherently. Ethical and environmental concerns also remain considerable challenges.

2. Can we use any battery life cycle testing equipment for all types of batteries

No, not all battery cyclers are suitable for use with all types of batteries. As battery’s chemistry and capacity changes, testing equipment must also be changed. In other words, specifications of testing equipment shall be compatible with that of battery. Testing equipment manufacturers mention categorically that a user can attach ‘these’ and ‘these’ types of batteries with ‘this’ model of tester.

3. Are there any international standards discussing battery life cycle testing?

Battery’s life cycle testing has evolved to become an important tool to improve battery’s design and performance. Accordingly, standards are also developed which detail requirements and procedures to conduct aging tests. For example, IEC 62133 sets requirements of testing for lithium ion batteries. This is widely recognized and used by manufacturers and regulators.

4. How long does it take to conduct aging test on a battery?

Aging tests are time consuming. One test might take few weeks to several months. That’s why it is recommended that you choose multi-channel tester if you have to test more than one battery.