効率損失を考慮しつつ、指定の消費電流でバッテリーの稼働時間を計算。mAh、Wh、アンペア時（Ah）の相互変換にも対応。
| 効率 | 稼働時間 | 消費電力量(Wh) |
|---|
容量をワット時に変換: Wh = (mAh × V) / 1000。負荷をワットに変換(W = V × A)。稼働時間(時間) = (Wh × 効率) / 消費電力(W)。
実際の稼働時間は理論値より短くなります。放電が進むにつれて電圧が低下し、低温では容量が減少し、また機器の消費電力が常に一定とは限らないためです。
Everything is normalised to watt-hours before dividing. Capacity becomes Wh as mAh × V ÷ 1000, as Ah × V, or is used directly when you select Wh. The load becomes watts as mA × V ÷ 1000, as A × V, or straight through when you select W. Runtime in hours is then Wh × efficiency ÷ watts. The mAh readout is the reverse trip, Wh × 1000 ÷ V, which is why voltage matters even for a Wh entry.
Battery voltage (V) is the input people get wrong most often, and it silently rescales both conversions at once; the field's note offers Li-ion ≈ 3.7 V, AA ≈ 1.5 V and lead-acid ≈ 12 V. Efficiency (%) defaults to 85 and stands in for regulator and heat losses. The table beneath re-runs the identical calculation at 100, 90, 85, 75 and 60% so you can read the spread instead of trusting one assumption.
This is a constant-current, constant-voltage model and real batteries are neither. Voltage sags as a pack empties, so usable watt-hours fall short of the nameplate figure; cold weather cuts capacity further; and alkalines in particular surrender a large share of their rated mAh at anything above a gentle draw. The device presets are illustrative starting points rather than measured discharge profiles, so treat every result as an optimistic upper bound.
About 12 hours 45 minutes at the defaults. 3000 mAh at 3.7 V is 11.1 Wh, a 200 mA draw is 0.74 W, and the 85% efficiency setting leaves 9.4 Wh usable. Without that haircut the ideal figure would be 15 hours.
Multiply by the pack voltage, then divide by 1000. A 10000 mAh bank at 3.7 V holds 37 Wh. That is why airlines quote watt-hours rather than mAh, and why two packs with identical mAh at different voltages store different energy.
Around 80 to 85%. Boosting a 3.7 V cell up to 5 V costs real energy, which is why a 10000 mAh bank typically delivers nearer 6000–6500 mAh at 5 V. The 85% default is a fair starting point for most regulated devices.
The model assumes a steady draw at a steady voltage. Real packs sag as they empty, cold weather cuts usable capacity, and most devices spike well above their average load. Alkaline cells suffer worst, losing a large share of rated capacity at higher currents.
No. The second holds over three times the energy, 60 Wh against 18.5 Wh. Milliamp-hours only compare meaningfully at the same voltage, which is exactly why the calculator converts both capacity and load to watt-hours before dividing.
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