IEEE 485 Service-Life Margin Calculator
IEEE 485 Service-Life Margin Calculator
Uptime · service life margin
A battery rated for exactly what you need has no margin at all
A published cycle rating is not a failure point — it is the point at which capacity has fallen to 80% of original. IEEE 450 and 1188 treat 80% as the end of useful life, and IEEE 485 recommends a 1.25× aging factor as a minimum when sizing, purely to cover that fade. So a battery rated for your exact requirement is already out of margin before you account for cold, poor charging, or a bad install.
How long the equipment itself will be in service — not how long you hope the battery lasts.
A solar site that discharges overnight and recharges daily is 1.0. Standby duty is far lower.
Lab ratings are measured at room temperature with controlled charging. Haircut them to whatever you actually believe.
1.25 is the IEEE 485 minimum. Raise it for cold climates, hard cycling, or unattended sites you cannot inspect.
Where each option sits
Position on the failure-rate curve
Battery failure characteristics follow a bathtub curve: elevated early failures, a long flat useful-life period, then a rising rate as cells wear out. The curve shape here is illustrative of that behaviour, not fitted to failure data for these specific products. A marker shows how far into its own rated life each option runs. Nothing is shown past 100%, because no one runs a unit beyond its rating — they replace it. A ×N label means the site re-enters the wear-out region that many times over the term, which is the part that generates unplanned failures rather than scheduled ones.
Cycle ratings are manufacturer figures at each product's own depth-of-discharge convention: sodium 10,000 at 85% DoD, budget LFP 4,000 at 100%, premium LFP 3,500, flooded GC2 approximately 1,100 at 50%, 4D AGM approximately 600 at 50%. LFP and lead-acid ratings are to the 80% capacity point per standard practice; the sodium rating is to 75% state of health per its datasheet — not the same endpoint. The tool reports whichever constraint — cycles or calendar years — runs out first (see note below the table for calendar-limit sourcing). The calculator does not model temperature, charge quality, or maintenance, all of which shorten real service life below the rating rather than extending it.
Uptime · service life margin
A battery rated for exactly what you need has no margin at all
A published cycle rating is not a failure point — it is the point at which capacity has fallen to 80% of original. IEEE 450 and 1188 treat 80% as the end of useful life, and IEEE 485 recommends a 1.25× aging factor as a minimum when sizing, purely to cover that fade. So a battery rated for your exact requirement is already out of margin before you account for cold, poor charging, or a bad install.
How long the equipment itself will be in service — not how long you hope the battery lasts.
A solar site that discharges overnight and recharges daily is 1.0. Standby duty is far lower.
Lab ratings are measured at room temperature with controlled charging. Haircut them to whatever you actually believe.
1.25 is the IEEE 485 minimum. Raise it for cold climates, hard cycling, or unattended sites you cannot inspect.
Where each option sits
Position on the failure-rate curve
Battery failure characteristics follow a bathtub curve: elevated early failures, a long flat useful-life period, then a rising rate as cells wear out. The curve shape here is illustrative of that behaviour, not fitted to failure data for these specific products. A marker shows how far into its own rated life each option runs. Nothing is shown past 100%, because no one runs a unit beyond its rating — they replace it. A ×N label means the site re-enters the wear-out region that many times over the term, which is the part that generates unplanned failures rather than scheduled ones.
Cycle ratings are manufacturer figures at each product's own depth-of-discharge convention: sodium 10,000 at 85% DoD, budget LFP 4,000 at 100%, premium LFP 3,500, flooded GC2 approximately 1,100 at 50%, 4D AGM approximately 600 at 50%. LFP and lead-acid ratings are to the 80% capacity point per standard practice; the sodium rating is to 75% state of health per its datasheet — not the same endpoint. The tool reports whichever constraint — cycles or calendar years — runs out first (see note below the table for calendar-limit sourcing). The calculator does not model temperature, charge quality, or maintenance, all of which shorten real service life below the rating rather than extending it.