Make every watt-hour count.
Use the cell voltage on the battery label. Efficiency combines assumed losses; sun hours are a scenario, not a forecast. Ageing, temperature, shading, conversion and charge limits change real output. Reserve power for essential communications.
Model details & unit conventions ↗Convert mAh to watt-hours with Wh = mAh ÷ 1,000 × volts, and see where 10,000 to 30,000 mAh banks sit against the 100 Wh and 160 Wh airline limits.
Estimate phone charges from a power bank by dividing usable watt-hours by the phone battery energy, with 60% and 80% scenarios for a 10,000 mAh bank.
Estimate daily solar charge from panel watts, equivalent sun hours and charging losses, with angle and cloud scenarios for a 10 W backpacking panel.
Why a phone or power bank delivers less energy in cold weather, how to model the loss as a lower efficiency scenario, and what to do on the trip.
Offline hiking checklist: save maps, test them in airplane mode, budget battery power, note daylight and leave a trip plan before you lose mobile signal.
UV water purifier explained: what portable UV devices kill, why cloudy water and battery power matter, and what UV leaves in the water.
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