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How many phone charges in a power bank?
A 10,000 mAh power bank does not charge a 5,000 mAh phone twice. Here is the real number.
Why it is fewer than you expect
Power banks quote mAh at their internal cell voltage (usually 3.6 or 3.7 V), but they boost it to 5 V or more for USB, and both the power bank and the phone lose energy as heat while charging. Comparing watt-hours (mAh × volts ÷ 1,000) and allowing for losses gives a realistic answer. Many phones list their battery in Wh or mAh in the settings or the spec sheet; the volts default here is typical of current phones.
Tips for an outage
- Keep power banks charged and top them up every few months.
- Turn on low-power mode, lower the screen brightness and turn off what you do not need.
- Text instead of calling — it uses less power and gets through busy networks more easily.
For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).
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Source: arithmetic (energy = capacity × voltage).