Power-bank recharge calculator
Advertised milliamp-hours cannot be compared across voltages; watt-hours make the energy comparable.
Wh
Wh
%
Complete recharges
4
- Equivalent total charges
- 4.93
- Usable delivered energy
- 59.20 Wh
- Energy after complete charges
- 11.20 Wh
Show the working
- Power-bank energy = 74
- Device battery energy = 12
- Delivered efficiency = 80
- Usable delivered energy = 74*80/100 = 59.2
- Complete recharges = floor(59.2/12) = 4
- Equivalent total charges = 59.2/12 = 4.933 33
- Energy after complete charges = 59.2-4*12 = 11.2
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- equivalent charges = bank watt-hours x efficiency / device watt-hours
Cable, voltage-conversion, temperature and standby losses are represented only by the efficiency input.