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Battery Life Calculator

Science & Engineering

mAh ÷ mA with real-world derating

Quick Answer

Battery Life Calculator: mAh ÷ mA with real-world derating. Battery Life Calculator uses standard science & engineering formulas to compute accurate results instantly.

Estimated runtime

4h 37min

15.4Wh × 90% efficiency = 13.9Wh usable ÷ 3W

Total energy15.4 Wh
Usable energy13.9 Wh
Runtime4.6 h
Battery current779 mA

Steps

  1. 1Energy = 4000mAh ÷ 1000 × 3.85V = 15.40 Wh
  2. 2Usable = 15.40 × 90% = 13.86 Wh
  3. 3Runtime = 13.86Wh ÷ 3W = 4.62h
  4. 4Current draw at battery = 3W ÷ 3.85V = 779mA

Typical device power

手机15W / 4Ah
蓝牙耳机5W / 500mAh
智能手表3W / 400mAh
平板20W / 8Ah
充电宝 1 万37W / 10Ah
笔记本56W / 5Ah
无人机90W / 5Ah
露营灯2W / 10Ah

💡 mAh alone can't compare batteries across voltages — always convert to Wh (mAh×V/1000). Airline limit: ≤100Wh carry-on freely, 100-160Wh needs approval. Real runtime is shorter in cold (Li-ion loses ~20% at 0°C) and with aging (~80% capacity after 500 cycles).

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How to Use

  1. Enter known quantities: fill values and confirm units in the Battery Life Calculator.
  2. Instant solution: unknowns solve live with the formula shown transparently.
  3. Use constant/material tables: standard physical constants and material data are listed on this page.
  4. Compare conditions: change inputs to compare scenarios.

Key Points

  • Battery Life Calculator is a free online science & engineering tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: mAh ÷ mA with real-world derating.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

Battery Life Calculator formula

Battery Life Calculator uses standard science & engineering formulas to compute accurate results instantly.

FAQ

How do I use the Battery Life Calculator?
Open the page and fill in the input fields — results update automatically. mAh ÷ mA with real-world derating.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on CODATA recommended constants and standard physics formulas. Last updated: 2025-07

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. Battery Life Calculator[EB/OL]. https://www.yijiansuan.com/en/c/science/battery-life

Results provided by this tool are for reference only and do not constitute professional advice.