OEM / ODM ENGINEERING TOOL
Battery Runtime Calculator
Estimate operating time from battery energy and average load, then apply your validated planning allowances.
Battery and load inputs
Enter average device-side power, not startup or peak power. Add conversion losses below.
Planning allowances
Defaults apply no losses or reserve. Enter an available-energy factor supported by pack testing for temperature, aging and cutoff. Do not deduct the same loss twice. Standby draw must exclude power already counted in the load.
Estimated operating time
Correct the highlighted inputs to calculate runtime.
- Ideal theoretical runtime
- 4.992 h
- Planning runtime
- 4.992 h
- Rated battery energy
- Energy after availability and reserve
- Estimated battery-side power
A sizing estimate, not a guaranteed runtime. Constant average-load calculation; excludes unentered losses, cell imbalance, BMS shutdown timing, transient voltage sag and changing operating conditions. Medical backup and mission-critical runtime require device-level validation.
Request a Runtime Review
The estimate is added to your requirements. Tell us the real device duty cycle, minimum input voltage, environment and end-of-life runtime target.
How the runtime calculation works
| Quantity | Formula | Meaning |
|---|---|---|
| Rated energy | V × Ah, or entered Wh | Nominal energy, not measured usable output. |
| Ideal runtime | Wh / average W | No conversion loss, reserve or standby allowance. |
| Planning energy | Wh × availability × (1 − reserve) | Percentages converted to fractions; use validated inputs. |
| Power-mode draw | Load W / efficiency + standby W | Efficiency excludes separately entered battery-side standby draw. |
| Current-mode draw | Nominal V × battery-side A + standby W | Current measured at the battery; no second efficiency deduction. |
| Planning runtime | Planning Wh / battery-side W | Estimate under the entered assumptions. |
For duty-cycled equipment, derive average load from each operating state’s power multiplied by its time fraction. Verify startup and stall current separately; a runtime result does not confirm current capability.
Runtime inputs OEMs should verify
Medical equipment
Validate essential operating modes, alarms, aged batteries, cutoff and reserve under the intended conditions.
Robotics and industrial equipment
Measure drive cycles, computing load, auxiliary power and idle draw. Check peak-current limits separately.
Cold-weather deployments
No universal low-temperature factor is applied. Request pack-level results at your temperature and load.
Frequently asked questions
Why is planning runtime different from theoretical runtime?
Theoretical runtime divides nominal energy by load without allowances. Planning runtime applies the availability, reserve, conversion efficiency and extra standby draw you enter. With default values the two are identical.
Should I enter device current or battery current?
The current method requires average battery-side current. Device current at a different regulated voltage is not interchangeable. Use the power method for a device-side load and enter the appropriate conversion efficiency.
Can I predict runtime at −40°C?
Not from temperature alone. Enter a tested available-energy factor for the actual cells, pack, temperature, load and cutoff. Include heater energy in the load or standby allowance where applicable.
Can I enter an end-of-life battery capacity?
Yes. Use measured end-of-life Wh or Ah, or apply an evidence-based availability factor to beginning-of-life energy. Do not apply the same aging reduction in both places. Increased resistance and voltage sag still require separate verification.
Does this confirm that the battery can power my equipment?
No. Voltage window, peak and continuous current, connectors, protection thresholds, charging and system validation also need to match.
How do I include sleep and active operating modes?
Calculate time-weighted average power from the complete operating cycle, including communication, sensors and standby. A single average cannot validate short high-current events.
Does the result guarantee medical backup runtime?
No. Test the complete device at the relevant load, environmental conditions, battery age and alarm thresholds. Use risk-based acceptance criteria rather than the calculator alone.
Related engineering tool
Battery Pack Configuration Calculator: estimate series/parallel cell count, voltage, capacity and nominal energy.
