This tool estimates your battery's current state of health based on usage patterns and age. Lithium-ion batteries lose capacity through two main mechanisms: cycling (charge and discharge) and calendar aging.
Enter at least one of these:
For better accuracy, provide both values.
Optional inputs:
The battery's current capacity as a percentage of its original capacity. New batteries start at 100%. Most manufacturers consider 70-80% the threshold for replacement in critical applications.
One cycle equals discharging the battery's full capacity. Two charges from 50% to 100% count as one cycle.
How much of the battery's capacity gets used per cycle. 100% DoD means full discharge. 50% DoD means using half the capacity. Deeper discharges accelerate degradation.
The calculator uses a non-linear degradation model based on battery research:
Cycle degradation follows a power law. Degradation rate decreases with cycle count (square root relationship) but increases with depth of discharge (squared relationship):
High cycle counts (>1500) trigger accelerated degradation with an additional factor.
Calendar aging progresses with the square root of time:
Batteries older than 8 years show accelerated aging.
When both factors exist, they interact rather than simply adding together:
The combined effect is typically 85% of their sum, reflecting overlapping degradation mechanisms.
