Battery energy (mAh to Wh)

Model: E = capacity × nominal voltage; usable = E × (DoD limit − reserve); I = P / V; C-rate = I / capacity

Show your work

1. Charge

   $$\mathrm{Ah}=\mathrm{mAh}/1000$$

   5,870 mAh / 1000 = 5.87 Ah

2. Energy in the pack

   $$\mathrm{Wh}=\mathrm{Ah}\times V$$

   5.87 Ah × 15.4 V = 90.4 Wh

The same steps an agent gets from the MCP server with explain: true.

Accuracy: Exact at the nominal voltage. Real packs deliver less when cold, old, or at high current.

When to use this: Use this when planning endurance or checking what a pack can carry: it converts capacity and voltage into watt-hours, subtracts the depth-of-discharge limit and the reserve you land with to give the energy you can actually use, and turns a power draw into a current and a C-rate you can compare against the cell's rating.

Limitations: It is nameplate arithmetic at the nominal voltage. A real pack delivers less when it is cold, old, or worked hard, its voltage sags under load, and the C-rate a manufacturer prints is not a promise at every state of charge. Transport and shipping rules count watt-hours the same way this does, but the limits themselves are the carrier's.

Worked example: A 5,870 mAh, 15.4 V pack. Source: add-drone-suite battery scenario: about 90.4 Wh. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

Review: Not yet independently reviewed by a Part 107 remote pilot.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.1, core 0.1.0. See this tool in the verification report.

Changes

• 2026-09-23, fixed: Plain-number results in a fixed unit now show that unit: the battery current reads 9.7 A where it read 9.7, and decibels, gigabytes, pulses per square meter, grams per kilogram, nautical miles per gallon, hours, nanoteslas, and minutes now carry their units too. The numbers themselves do not change. Each tool's patch version went up. Changelog
• 2026-09-19, changed: Battery energy (mAh to Wh) is now stable. It matches the FAA PackSafe worked example (12 V and 8 Ah is 96 Wh) and 19 vectors from a separate implementation. Results are unchanged. Changelog

Checked against: 21 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

• Principles of Helicopter Aerodynamics, Leishman, J. G., Cambridge University Press, 2nd edition. Chapter 2 (momentum theory: ideal hover power T^1.5/√(2ρA), figure of merit).