What it is
Battery degradation calculators help engineers predict how a battery’s capacity will decline over its service life. The model used here relies on three driving factors that are routinely measured in the lab: the number of charge‑discharge cycles, the average depth‑of‑discharge (DOD), and the operating temperature. A simple semi‑empirical formula relates these inputs to a linear fade term while an independent calendar‑aging term accounts for time at rest. The calculator outputs total capacity loss as a percentage and, using a supplied initial Ah rating, the remaining usable energy in familiar units. Such foresight is critical for sizing packs, defining warranties, or estimating replacement intervals.
How to use it
Fill in the initial nominal capacity of the cell or pack in ampere‑hours (Ah). Enter the average DOD as a percentage and the total number of cycles expected before retirement. Specify the constant operating temperature in degrees Celsius and any calendar days spent at rest without cycling. The tool instantly reports how many percent of capacity will be lost and what Ah remains, allowing you to verify design margins or plan maintenance schedules.
Worked example
With a nominal cell of 50 Ah, an average DOD of 80 % and one‑year (365 days) at rest the calculator proceeds as follows: 1. Convert the DOD to a fraction: 0.80. 2. Compute the cycle‑dependent fade term: 0.0005 × 3000 × 0.80 × e^(0.005×25). The exponential evaluates to e^0.125≈1.13315, giving 0.0005×3000×0.80×1.13315≈1.360 %. 3. Compute the calendar aging term: 0.00005×365=0.018 %. 4. Total capacity fade is 1.360 %+0.018 %=1.378 %. 5. Remaining usable energy equals 50 Ah minus (1.378 % of 50 Ah) → 49.311 Ah. The tool displays these two figures, letting the designer confirm that capacity loss stays within acceptable limits.
Inputs
- Initial Capacity (Ah): 50
- Average Depth of Discharge (%): 80
- Total Charge‑Discharge Cycles: 3000
- Operating Temperature (°C): 25
- Calendar Days at Rest: 365
Result
- Capacity Fade (%): 1.378
- Remaining Capacity (Ah): 49.311
Frequently asked questions
How accurate is the degradation estimate?
The model is a simplified empirical representation based on typical commercial cells; it captures the main trends of cycle‑dependent and calendar aging but ignores chemistry‑specific nuances. For detailed life prediction a full electrochemical or stochastic model would be required.
Can I input a temperature profile instead of a constant?
The current calculator assumes a steady operating temperature. If you need to account for variable temperatures, collect a dataset of daily average temperatures and use the built‑in dataset feature (if added later). For now, use the mean value that best represents critical periods.
Will different chemistries affect the constants?
The constants k1=0.0005, k2=0.005, and a0=0.00005 were chosen to reflect generic Li‑ion cells. If you have precise data for a specific chemistry (e.g., NMC, LFP), adjust these values accordingly by scaling the cycle or calendar terms.