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Physics

Battery Runtime Calculator

Runtime = (Capacity × V × efficiency) / Power. Free online Battery Runtime Calculator. Calculate battery runtime online — fast, accurate, mobile-friendly, no si

Runtime (hours)
17

Derivation

  1. ├── 01GivenAh = 100, V = 12, W = 60, eff = 85
  2. ├── 02Formulat × a × (e.eff / 100) / n
  3. ├── 03Substitutet × a × (e.85 / 100) / n
  4. └── 04Compute Runtime (hours)17
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§01What is

Understanding the Battery Runtime Calculator

The Battery Runtime Calculator computes Runtime (hours) from 4 inputs: capacity (ah), voltage, load (w), efficiency (%). Runtime = (Capacity × V × efficiency) / Power.

Physics is the toolkit for turning a real-world observation into a prediction. Whether it’s a falling object, a moving car, or a stressed beam, the equations here are the same ones every engineer relies on. The Battery Runtime Calculator sits in that toolkit — it runtime = (Capacity × V × efficiency) / Power. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

t × a × (e.eff / 100) / n

Where

Ah
Capacity (Ah)
V
Voltage
W
Load (W)
eff
Efficiency (%)
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Capacity (Ah) = 100, Voltage = 12, Load (W) = 60, Efficiency (%) = 85.

  1. 01Start by noting the input — Capacity (Ah): 100.
  2. 02Start by noting the input — Voltage: 12.
  3. 03Start by noting the input — Load (W): 60.
  4. 04Start by noting the input — Efficiency (%): 85.
  5. 05Substitute these values into the formula: t × a × (e.eff / 100) / n
  6. 06Compute Runtime (hours): the calculator returns 17.
  7. 07Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Battery Runtime Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Capacity (Ah) halved

Ah = 50 (from 100)

Keep every other input at its default and halve the capacity (ah). See how runtime (hours) responds.

  1. 01New Capacity (Ah): 50
  2. 02Baseline Runtime (hours): 17
  3. 03New Runtime (hours): 8.5
  4. 04Runtime (hours) decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Capacity (Ah) doubled

Ah = 200 (from 100)

Keep every other input at its default and double the capacity (ah). See how runtime (hours) responds.

  1. 01New Capacity (Ah): 200
  2. 02Baseline Runtime (hours): 17
  3. 03New Runtime (hours): 34
  4. 04Runtime (hours) increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Voltage halved

V = 6 (from 12)

Keep every other input at its default and halve the voltage. See how runtime (hours) responds.

  1. 01New Voltage: 6
  2. 02Baseline Runtime (hours): 17
  3. 03New Runtime (hours): 8.5
  4. 04Runtime (hours) decreases by 50% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Voltage doubled

V = 24 (from 12)

Keep every other input at its default and double the voltage. See how runtime (hours) responds.

  1. 01New Voltage: 24
  2. 02Baseline Runtime (hours): 17
  3. 03New Runtime (hours): 34
  4. 04Runtime (hours) increases by 100% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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