Learn one unit and the rest follows#
Watt-hours. Not milliamp-hours, which are printed at the 3.7 volt cell level and therefore compare nothing useful, and not "phone charges", which depends entirely on the phone.
To convert: watt-hours equal milliamp-hours times 3.7, divided by 1,000. A 10,000 mAh bank holds about 37 Wh. Airlines cap a carry-on battery at 100 Wh without approval, which is roughly 27,000 mAh, and that limit is the reason the number matters even if you never do the arithmetic for your own trip.
Once every device is expressed in watt-hours per day, the whole problem collapses into arithmetic: add the daily draws, multiply by nights, divide by 0.85 for conversion losses, and apply a further derate if it will be below freezing. That is what the power budget calculator does.
Where to start#
- Power banks and battery sizing for the budgeting method
- Headlamps and the FL1 standard for reading a lamp specification honestly
- Solar panels for camping for realistic harvest figures
- 12 volt power and fridges for the vehicle-based end of the topic
Frequently asked questions#
What size power bank for a weekend?#
For one phone in airplane mode, a headlamp and nothing else, a 5,000 mAh bank (about 18 Wh) is comfortable for two nights with margin. Heavy navigation, a satellite messenger and a second phone push a three night trip towards 40 to 60 Wh.
Are solar panels worth it for camping?#
Below about four days, almost never: the panel weighs more than the extra battery capacity it replaces. Above a week in open country, or on any trip with a compressor fridge, solar starts to be the only sensible answer.
How many lumens do I need in a headlamp?#
For camp chores, 30 to 100 lumens is plenty and 400 is dazzling in a tent. For night hiking on uneven ground, 200 to 350 with a beam that mixes flood and spot. Run time at a usable brightness matters far more than peak output.
Why does my headlamp claim 200 hours of run time?#
Because FL1 measures run time to the point where output has fallen to 10 percent of the initial figure. A lamp can spend most of that quoted time delivering a tenth of its headline brightness. The headlamp guide breaks down every figure on the box.