Battery Runtime Calculator
Estimate ideal battery life, determine the battery capacity needed for a target operating time, or calculate the average load current supported by a known battery. Use the result for early power budgeting, portable-device design, and battery selection.
Engineering tool
Battery Runtime Calculator
Estimate ideal battery runtime, required capacity, or allowable load current with automatic engineering-unit conversion.
Primary Result
10 h
Result console
- Runtime
- 10h
- Minutes
- 600min
- Seconds
- 36,000s
- Days
- 0.416667days
- Battery capacity
- 3Ah
- Load current
- 300mA
Battery status
Good
Formula: Runtime = Capacity / Current
Scientific notation: 1.0000e+1 h
The ideal runtime supports a typical working-day duty cycle. Add capacity margin for real battery behavior.
Formula reference
Battery Runtime Formulas
Use amp-hours, amperes, and hours as the consistent base units.
Runtime = Capacity / CurrentCapacity = Runtime × CurrentCurrent = Capacity / RuntimeVariable definitions
- Capacity
- available battery charge in amp-hours
- Current
- average load current in amperes
- Runtime
- ideal operating time in hours
Worked Examples
Calculate Runtime
3000 mAh / 300 mA = 10 hours.
Required Capacity
500 mA × 12 hours = 6000 mAh.
Load Current
10 Ah / 20 hours = 0.5 A, or 500 mA.
Engineering Notes
- Battery runtime is an ideal estimate based on average current and nominal capacity.
- Actual runtime depends on battery chemistry and its discharge curve.
- Temperature affects usable capacity and voltage performance.
- Battery aging reduces available capacity over repeated cycles and calendar time.
- High discharge rates can reduce effective runtime and increase voltage sag.
- Always include safety margin for conversion losses, peak loads, cutoff voltage, and product reserve.
Support reference
FAQ
How do I calculate battery runtime?
Divide battery capacity in amp-hours by average load current in amperes. The ideal result is runtime in hours.
Why is actual runtime shorter?
Usable capacity falls with conversion loss, battery cutoff voltage, peak loads, self-discharge, aging, temperature, and discharge-rate effects.
Does temperature affect battery life?
Yes. Low temperature commonly reduces available capacity and voltage performance, while sustained high temperature accelerates battery aging.
Can I use this for lithium batteries?
Yes, for an initial capacity-based estimate. Verify the cell discharge curve, protection cutoff, load profile, and manufacturer ratings for the actual design.
What units are supported?
Capacity supports mAh and Ah; current supports µA, mA, and A; runtime supports seconds, minutes, hours, and days.
Documentation
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