Cycle Life by Model: Reading a LiFePO4 Spec Sheet Honestly
A spec sheet that gives a cycle-life figure without a condition, without a capacity-remaining level and without a discharge rate is not giving a comparable figure. This article explains how to read a cycle-life figure honestly, using the listed figures on this site as examples. It does not give a cycle-life promise for the whole range, because cycle figures are stated per model with their conditions.
The three parts of a cycle figure
A complete cycle-life figure has three parts: the number of cycles, the test condition, and the capacity remaining at the end of the test. For example, a figure of 2000 cycles at 0.2C charge and discharge down to 70 percent capacity gives all three parts: the number, the rate and depth condition, and the remaining capacity. A figure that gives only the number, without the condition and the remaining capacity, cannot be compared with another figure, because the missing parts could hide a stricter or a looser test. The listed figures on this site illustrate why all three parts matter: some listed models state 2000 cycles under that stated condition, one listed model states more than 6000 cycles under a different condition, and a home pack states 6000 or more cycles under its own listed condition.
Cycle life is measured under a stated test condition, and the condition matters as much as the headline number. A figure measured at a low discharge rate and a shallow depth of discharge cannot be compared directly with a figure measured at a higher rate and a deeper depth, because the tests differ. A buyer comparing models should therefore read the condition behind each figure, and should ask for any missing detail — rate, depth of discharge, capacity remaining and temperature — before ranking two models against each other.
Rate, depth and temperature in the test
The discharge rate in a cycle test affects the result, because a higher rate generally stresses the cells more than a lower rate. A cycle figure measured at 0.1C cannot be compared directly with a figure measured at 0.5C or 1C, because the test conditions differ. Depth of discharge also affects the result, because a deeper discharge generally leaves fewer cycles available than a shallower discharge. Temperature during the test is a third factor: a cycle figure measured at a controlled room temperature may not describe a pack used in extreme heat or cold. A buyer reading a spec sheet should therefore look for the rate, the depth of discharge, the capacity remaining and the temperature, where those details are given.
Depth of discharge describes how much of a pack's capacity is used before it is recharged. Using a smaller depth of discharge generally leaves more cycles available, while deep discharges use more capacity per cycle. Cycle-life figures therefore only make sense with the test condition attached, such as the discharge rate and the capacity remaining at the end of the test. This site reports cycle life per model with its stated condition, and does not convert one model's figure into a range-wide claim.
Cycle life in use is not cycle life in the test
Cycle life in the test is measured under controlled conditions, while cycle life in use depends on the actual load profile, temperature, charging setup and maintenance. A pack used within its listed temperature and current ranges, and charged with the correct voltage and current for its model, is more likely to approach its listed cycle figure than a pack used outside those ranges. Calendar ageing also affects useful life in use, because a pack loses capacity over time even when it is not cycled, especially at high temperatures or at a high state of charge for long periods. A pack that is rarely cycled may therefore still need replacement after a number of years, even though it has not reached its cycle-life figure.
Temperature is a check that is often overlooked when a pack is chosen by capacity alone. The listed temperature ranges on each product page state the charging, discharging and storage ranges for that model, and those ranges should be checked against the installation location and the climate. Charging below the listed charging range should not be attempted without a specific confirmation for the model, because charging in cold conditions can damage the cells. If charging in cold conditions is a regular requirement, the enquiry should state the lowest charging temperature.
Comparing models honestly
To compare two models honestly, list each model's cycle figure together with its rate, depth of discharge, capacity remaining and temperature, where those details are given. If a model does not give a cycle figure, do not borrow a figure from another model; instead, ask for the figure and its condition in the enquiry. If two models give figures under different conditions, do not rank them by number alone; instead, ask which condition is closer to the intended use, and consider that model's figure as the more relevant one for that use. The product pages on this site keep each model's cycle figure with its stated condition for exactly that reason.
For a business enquiry, the most useful details are the system voltage, the capacity, the expected discharge current, the operating temperature range and the physical space available. A pack that fits on paper can still fail in use if the discharge current, the temperature range or the terminal layout does not match the application. That is why this site asks buyers to confirm specifications per model, rather than selecting from a generic table.
What this article does not do
This article does not give a cycle-life figure for the range, because cycle figures are stated per model with their conditions. It does not recommend a model based on cycle life alone, because cycle life is only one factor alongside voltage, capacity, current limits, dimensions and protection. It does not state a selling figure, because this site does not list fixed selling figures. Those limits are stated openly, so a reader does not mistake a general cycle-life discussion for a model-specific lifespan promise.
Quotations are confirmed per order. Minimum order quantity and lead time are unavailable on this site, so they are not stated as company policy and must be confirmed per model in the enquiry. This site does not list fixed selling figures, because a figure depends on the model, the quantity and the order terms. A quotation should list the model, the quantity and the specification confirmed for that model, so the buyer and the manufacturer are working from the same description.
Enquiry checklist
Before sending an enquiry, note the voltage, capacity, quantity, application and any required certification document. State whether the pack will be used indoors or outdoors, and whether a display or a particular terminal type is needed. Minimum order quantity and lead time are unavailable on this site and are confirmed per model in the enquiry. Quotations are confirmed per order.
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Frequently asked questions
How do I get a quotation?
Send an enquiry with the voltage, capacity and quantity you need, plus the application. Quotations are confirmed per order, and specifications are confirmed per model before payment. This site does not list fixed selling figures.
What certification documents can you provide?
ISO 9001 is stated by the company. Certificates are available upon request. If a buyer needs a certificate for a specific model, ask for it in the enquiry and name the model, so the correct document can be checked.
Are the specifications on this page valid for every model?
No. Specifications are shown per model and must not be read across the whole range. Where a value is not listed for a model, the page says to confirm per model rather than filling in a generic figure.