Battery Cycle Life: The Test Conditions Behind the Number
Why depth of discharge, temperature, C-rate, and end-of-life criteria must accompany every cycle-life claim.
A cycle-life number without test conditions is not enough for a technical or procurement decision. Two batteries can carry similar headline figures while being tested under very different conditions.
The four conditions to request
1. Depth of discharge
Depth of discharge describes how much of the battery’s available capacity is used in each cycle. A shallow cycle is generally less demanding than a full cycle, so the stated DoD belongs beside the cycle count.
2. Charge and discharge rate
Current affects cell temperature and electrochemical stress. Ask for the charge and discharge rates used in the test and whether those rates resemble the intended application.
3. Ambient and cell temperature
Temperature has a material effect on performance and aging. A useful test summary identifies the relevant temperature conditions rather than presenting the result as universally applicable.
4. End-of-life threshold
Cycle life is commonly counted until retained capacity reaches a defined threshold. The threshold must be stated so that two values can be compared on the same basis.
A better procurement question
Instead of asking only, “How many cycles does it last?”, provide the expected daily operating profile, charge method, peak current, ambient range, and required service life. The supplier can then explain which test data is relevant and where engineering margins are needed.
How Egroupinus presents reference values
The product pages on this site use reference values to support early project discussion. The final product specification should state the agreed configuration, operating limits, test conditions, and acceptance criteria.
Apply this to your project