How long will a 20,000 mAh power bank run a USB LED lantern?
About 18 h 30 min on a medium setting (3 W), from 16 h 2 min to 20 h 58 min depending on how efficient the bank is.
An LED lantern lights a room for an evening, and a power bank keeps it going for many. A 20,000 mAh bank holds about 74 Wh at its 3.7 V cells, of which about 75% typically reaches the USB port.
The numbers
| Setting | Worst case | Typical | Best case |
|---|---|---|---|
| Low (1 W) | 2 days | 2 days 8 h | 2 days 15 h |
| Medium (3 W) | 16 h 2 min | 18 h 30 min | 20 h 58 min |
| High (5 W) | 9 h 37 min | 11 h 6 min | 12 h 35 min |
LED lanterns are so efficient that the bank lasts days on a low setting. The figures here are for a lantern plugged into the bank; one with its own battery simply recharges from it.
Other sizes
| Power bank | Energy | Typical |
|---|---|---|
| 10,000 mAh | 37 Wh | 9 h 15 min |
| 20,000 mAh | 74 Wh | 18 h 30 min |
| 26,800 mAh | 99 Wh | 24 h 47 min |
| 40,000 mAh | 148 Wh | 37 h |
Where to buy
USB LED lantern
A 20,000 mAh power bank
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When a power bank is not enough
A power station runs the same job from a mains socket, for far longer, and runs the things a power bank cannot: the fridge, the boiler's electrics, a mains electric blanket. For example, the Anker SOLIX C300 runs LED camping lights for about 18 h 53 min.
If this is for a power cut
For light alone, you do not need a power station at all.
Plug-in power failure lights. They live in a socket as a night light, charge themselves, and switch on the moment the mains goes off, so you are never hunting for a torch in the dark.
Look for: A built-in battery you can pull out and carry as a torch, and a UK three-pin plug if you are in the UK.
Battery motion-sensor lights. Stick-on lights on the stairs and landing come on when someone walks past, so nobody climbs stairs in the dark, which is when older people fall.
Look for: Rechargeable or AA batteries, and a warm white setting that is not too bright at night.
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More: the power cut essentials list (US edition).
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