Getting the most out of your lithium-ion batteries
Batteries don’t last forever, but if they are used properly and tested and maintained frequently, you can ensure they will last a long time – and perhaps get some extra life out of them!
When aging is referred to regarding a battery, it includes both calendar aging and battery cycling. Calendar aging occurs during both battery storage and battery service. It is greatly influenced by the type of positive electrode material, temperature, and the operating voltage the battery has encountered over time. Cyclic aging affects both the positive and negative electrodes. The rate at which the battery ages is also dependent on both the frequency and depth of cycling and the rate of charge.
Both forms of aging lead to battery degradation and failure. Yet, it’s important to note that Li-ion batteries don’t just fail due to aging.
Other Li-ion failure modes include short circuiting, over discharge, overcharge, thermal runaway, and electronic failures. The good news is that these batteries have built-in battery management systems (BMS) that are intended to maintain battery safety and reduce the likelihood of catastrophic failure by monitoring things like voltage, temperature, rate of discharge, and rate of recharge. However, there are times when the BMS isn’t enough to discover problems before they lead to battery failure.
“In order to reduce failures, Li-ion batteries must be properly tested and maintained, particularly when they are used in cyclic applications. ”
Maintenance is key
In order to reduce failures, Li-ion batteries must be properly tested and maintained, particularly when they are used in cyclic applications.
In cyclic applications, the battery string discharges and recharges on a regular cycle. An example is an energy storage application such as solar and wind energy where the batteries are charging and discharging on a daily schedule. As a result, failures can occur in Li-ion strings in these cyclic applications due to electronic failures, poor connections, or bad cells. To identify these issues before they lead to battery failure, you need to measure each battery’s voltage and impedance. This allows you to find any batteries that are dissimilar to the rest of the string, allowing you to isolate any potential problems.
Test and measurement
Having the right tester is important when trying to assess why a string is failing. The tester needs to be able to perform voltage and impedance measurements on all Li-ion batteries. One such instrument is Megger’s BITE5. This handheld battery tester enables you to store results and trend them over time for each cell, and it can measure and record the output of solar cells and solar combiner boxes up to 1000 V DC.
The BITE5 is the latest battery tester from Megger, and it can measure and record AC voltage up to 600 V, DC voltage up to 1000 V, voltage ripple, DC current, AC current, and temperature. It can also perform impedance testing on cells up to 200 V, enabling you to identify faulty cells.
The BITE5 can also be used in place of a battery voltage monitor (BVM) to support discharge testing performed with the Megger TORKEL, measuring and recording voltage, DC current, impedance, and temperature of each cell throughout the discharge process The BITE5 reduces the set-up time involved and eliminates the concern of clips falling off the cell when using the BVM.
Testing and maintaining Li-ion batteries with the appropriate equipment is key to preventing battery failures and ensuring that the battery works optimally for its entire lifetime in operation.