Battery life forecast: state of health (SOH) and remaining life calculator
Enter the measurements of your lead-acid, nickel, lithium or sodium battery and get its state of health (SOH), estimated remaining life and a diagnosis to IEEE and IEC, with a PDF, DOCX or ODT report.
Your battery life forecast Enter the data and measurements of your lead-acid, nickel-cadmium, NiMH, lithium or sodium-ion battery and get its state of health (SOH), estimated remaining life and an indicative diagnosis according to IEEE and IEC criteria, with a printable report. You can ask an AMPERIS engineer to review it. Forecast my battery's life Close the diagnosis
What this tool does
It evaluates a battery with whatever data you have and returns three things:
- The verdict, with its severity and the action required.
- The state of health (SOH): capacity SOH (SOH-C), if a discharge test is available, and internal resistance SOH (SOH-R) as a warning indicator.
- The estimated remaining life: the years left until the end of life for its chemistry, with the expected year, a range and a confidence level.
It also gives one card per indicator with the applicable standard, actions sorted by urgency, the reference test plan and the right instrument for the measurement that is missing. The report can be printed or downloaded as PDF, DOCX (Word) or ODT (LibreOffice).
Chemistries and criteria
| Chemistry | End of life by capacity | Standards applied |
|---|---|---|
| Vented lead-acid (VLA) | 80 % of rated | IEEE 450 |
| VRLA lead-acid (AGM and GEL) | 80 % of rated | IEEE 1188 · IEC 60896-21/-22 · IEC 61056-1 |
| Nickel-cadmium | 80 %, after reconditioning | IEEE 1106 · IEC 60623 |
| Nickel-metal hydride | Per manufacturer | IEC 61951-2 |
| Lithium-ion and sodium-ion | 80 % in backup · 70 % in BESS and EV | IEEE 2962 · IEC 61960 · IEC TS 62933-3-1 |
By default it applies Best Practices, Amperis’ compilation of the international standards and of battery manufacturers’ recommendations. Where a specific standard differs, the result says so.
How remaining life is estimated
It combines three estimates and keeps the least favourable:
- Capacity trend: the loss per year between two tests, or since commissioning, projected to end of life. Remaining life ≈ (current SOH-C − end of life) ÷ annual capacity loss.
- Calendar: the manufacturer’s design life corrected for the average operating temperature, minus the battery’s age. In lead-acid, every 8 °C above 25 °C halves the expected life.
- Cycles: in cyclic service, the rated cycles left at the current rate of use.
Example, using the data built into the tool: a 6-year-old 48 V VRLA battery with an SOH-C of 87.1 % has lost about 2.2 points a year. It has about 3 years left until 80 %: fit, under watch, with end of life expected around 2029.
Your data
The diagnosis is calculated in your browser and is not stored. Nothing is sent unless you expressly ask an Amperis engineer to review the report: in that case the diagnosis reaches our technical department together with the contact details you enter.
What this tool does not do
- It does not replace a capacity test. Without one, resistance SOH is an indicator, not a measurement of backup time.
- It does not know your specific battery. The manufacturer’s voltages, tolerances and curves always prevail.
- It does not predict sudden failures. The forecast is an extrapolation: in lead-acid, capacity drops faster as end of life approaches, so repeat the test as often as the standard requires and update the forecast.
Further reading and instruments
The article Battery life forecast explains state of health, the full set of standards and the criteria for each chemistry. To size a new bank or work out its backup time, use the battery sizing and backup time calculator.
The measurements the tool asks for are made with dischargers and capacity analysers such as the BLU-C or the XD, with battery testers for internal resistance and with the BVS cell monitor for cell voltages.
Indicative result. The calculation runs in your browser and is not sent to any server. This website may contain errors or omissions: before making any decision about an installation, the information must be checked and validated by a qualified engineer. The battery and circuit breaker diagnostic tools run on Amperis servers; calculations are not stored unless you expressly choose to do so. Legal notice and terms of use
Frequently asked questions
- What is the difference between state of charge (SOC) and state of health (SOH)?
- State of charge tells you how much energy is available right now and changes with every charge and discharge. State of health tells you how much of its original capacity the battery retains and changes slowly, as it ages. A battery charged to 100 % with an SOH of 60 % delivers only 60 % of the backup time it was designed for.
- Can I use the tool without a capacity test?
- Yes. The tool only evaluates what you have measured: with internal resistances, voltages, temperatures or the battery’s age you get a diagnosis and a remaining-life estimate, and the capacity test is listed as pending, together with the standard that requires it. Forecast confidence goes up when a test is available, because it is the only measurement that proves the actual backup time.
- When should a battery be replaced according to the standards?
- For vented and VRLA lead-acid and for nickel-cadmium, when capacity falls below 80 % of rated (IEEE 450, IEEE 1188, IEEE 1106); nickel-cadmium is reconditioned before being written off. For lithium it depends on the application: 80 % in backup service and, typically, 70 % in energy storage (BESS) and electric vehicles.