A Cycle Number Is a Test Result, Not a Promise
Cycle life is the most quoted and least understood figure on a battery datasheet. A statement such as 2000 cycles sounds like a fixed property of the product, but it is the result of one specific laboratory test. Change the depth of discharge, the temperature, the charge rate or the end-of-life threshold, and the same physical pack produces a different number. Buyers who understand this read cycle life as a set of conditions first and a figure second, and they compare two LiFePO4 battery offers only when the conditions match.
What Counts as One Cycle
Testing practice counts a cycle as one full charge and discharge, but real service rarely matches. A system that swings from full to 70 percent and back every day completes roughly a third of a cycle in laboratory terms, so partial cycling stretches calendar time considerably. Most datasheets and warranty documents count equivalent full cycles, meaning total discharged energy divided by nameplate capacity, rather than days of use. When you project service life from a cycle figure, convert your own duty profile into equivalent cycles first; the result is often several times longer than a naive day count suggests.
The Conditions That Move the Number
Four variables dominate every cycle life test:
- Depth of discharge: deeper cycles consume more life per event than shallow ones
- Temperature: cells age fastest when cycled hot, and data measured near 25 degrees Celsius does not transfer directly to a hot enclosure
- Charge and discharge rate: high-rate cycling stresses cells and shortens life relative to gentle rates
- End-of-life threshold: a test that stops at 80 percent remaining capacity reports a smaller number than one that runs the same cells down to 60 percent
Two suppliers can both write 2000 cycles on the same class of cell and still be describing different products, if one tested at 80 percent depth of discharge to 80 percent capacity and the other at 50 percent depth to 60 percent. The conditions belong on your comparison sheet next to the number, every time.
Reading Two Datasheets Fairly
The fairest quick method is to convert both offers to total energy delivered before end of life. As an illustration of the method: a pack stated at 2000 cycles to 80 percent remaining capacity, tested at 80 percent depth of discharge, delivers about 1600 nameplate-equivalent kilowatt-hours per rated kilowatt-hour. A pack stated at 3000 cycles at 50 percent depth of discharge to 70 percent remaining capacity delivers a broadly similar total, despite the larger headline. The two packs may be closer than their datasheets suggest, or further apart; either way, the arithmetic reveals it and the sample test confirms it.
Cycle Life Versus Calendar Life
A pack that sits mostly full in a backup role cycles rarely but still ages, because time spent at high voltage and elevated temperature consumes life on its own. This calendar aging is separate from cycle aging and dominates in standby applications. For a buyer, the practical consequence is that a backup product should specify its storage state of charge and its thermal environment as carefully as a daily-cycling product specifies depth of discharge. Ask suppliers which limit they expect to bind first for your application, the cycles or the calendar, and ask for the reasoning.
Turning Cycles Into Years
Dividing cycles by cycles per day gives a first estimate that is easy to defend in a purchasing meeting. One cycle per day at 2000 equivalent cycles reaches the end-of-life threshold in about five and a half years, and partial cycling extends that proportionally. These projections support sourcing decisions, but they are not warranty terms. What counts as a cycle, how capacity is measured in a claim and what compensation applies are commercial conditions that each buyer confirms separately, and in writing, before the figure is passed downstream to customers.
Partial Cycles in Daily Service
Most installed systems never see a full cycle. A home storage bank that fills from solar and empties into the evening load may move between 100 and 40 percent, completing well under one equivalent cycle per day. Recording that fraction for a representative week gives a buyer a realistic cycles-per-year figure, and multiplying it by the confirmed cycle count gives an expected service span in calendar terms. The exercise also shows which products in a range genuinely need the longest cycle life and which are limited by calendar aging instead, which is useful when allocating budget across a product line.
Catalog Figures and Confirmation
The YueQi catalog states cycle life of 2000 cycles or more for its 12.8V and 25.6V LiFePO4 pack families, a level consistent with mainstream LiFePO4 cells in this class. The test conditions behind the published figure, including depth of discharge, temperature, rate and the end-of-life threshold, are to be confirmed in writing for each model before a buyer prints the number in downstream datasheets, listings or warranty documents. This is standard practice across the trade: a manufacturer publishes a headline, and the buyer obtains the conditions behind it in a documented form.
Questions to Put to Any Supplier
- At what depth of discharge, rate and temperature was the cycle figure measured?
- What remaining capacity defines end of life in the test?
- Does the figure come from cell-level testing, pack-level testing or the cell specification?
- How does the figure change at the temperature my product will actually see?
- What capacity measurement method applies in a warranty claim?
Where YueQi Fits
YueQi New Energy, based in Zhongshan, Guangdong, produces 12.8V and 25.6V deep cycle packs, 51.2V mobile storage batteries, home energy storage units and portable power stations, all on LiFePO4 chemistry chosen for daily-cycling duty. Buyers planning multi-year product lines can request the cycle life test basis per model, confirm it in writing, and build their own customer-facing claims on confirmed conditions instead of headline numbers.
Summary
A cycle life figure is a description of a test, not a property that travels with the product. Read the depth of discharge, temperature, rate and end-of-life threshold before comparing offers, convert competing figures to one basis, and project service life from your own duty profile. Conditions obtained in writing turn a marketing number into a purchasing argument.
Next step
Send your application, target specification and estimated quantity with your inquiry, and we will confirm matching products, samples and document requirements in writing. See the product lines or request a quote.