Power Banks for off-grid
The number printed on a power bank is the most misleading spec in outdoor gear. A 10,000 mAh bank does not charge a 5,000 mAh phone twice. Here's the conversion the box leaves out, the three sizes worth owning, and when you should skip the power bank and get a small power station instead.
How to read this guide: these are researched gear classes and examples, not firsthand product tests. Purchase links are paused until exact models and retailer destinations are verified.
How this guide was built: these picks aren't based on our own lab runs. They come from manufacturer specs, battery physics, FAA and TSA rules, and patterns we see across thousands of long-term owner reviews. Where a number below is an estimate, it says "about" or "roughly".
mAh is not the number you want
Power banks are rated in milliamp-hours (mAh) at the internal cell voltage, about 3.6–3.7 V. Your phone charges at 5 V or higher. Convert to watt-hours (Wh) and the rating starts to mean something: mAh × 3.7 ÷ 1,000 = Wh. A 10,000 mAh bank holds about 37 Wh.
Then take off the conversion losses. Voltage step-up, cable resistance and heat in the phone all cost energy. In practice you deliver roughly 60–70% of the rated capacity to the device. A modern phone battery holds about 12–19 Wh, so:
| Bank or device | Notes | Real-world yield |
|---|---|---|
| 10,000 mAh (~37 Wh) | the ultralight standard | ~1.5–2 phone charges |
| 20,000 mAh (~74 Wh) | the weekend workhorse | ~3–4 phone charges |
| 26,800 mAh (~99 Wh) | the largest you can fly with freely | ~4–5 charges, or ~1 laptop |
| Headlamp, 1,500–3,000 mAh | rechargeable lamps | ~5–10 refills from 10K |
| GPS / satellite messenger | small internal cells | many refills; trivial load |
| Wi-Fi router in an outage | about 6–12 W | ~5–7 hours from 99 Wh |
Rule of thumb for the trail: plan on one full phone charge every one to two days if you keep the phone in airplane mode and use it for maps and photos. That makes a 10,000 mAh bank enough for a 3–4 day trip, and a 20,000 mAh bank enough for a week.
The comparison
| Class | Capacity | Typical weight | USB-C PD | Flies? | Best for |
|---|---|---|---|---|---|
| Ultralight 10K | ~37 Wh | 150–200 g | 18–20 W | ✓ | Thru-hikes, fast packing |
| Workhorse 20K | ~74 Wh | 320–450 g | 20–30 W | ✓ | Weekends, group trips |
| Laptop-class 25–27K | ~90–99 Wh | 500–650 g | 65–140 W | ✓ | Car camping, remote work, outages |
| Small power station | 200–300 Wh | 2.5–3.5 kg | 60–100 W | ✕ cargo only | Multi-day outages, CPAP |
Why weight per watt-hour matters: thru-hikers favor carbon-shell 10K banks such as the Nitecore NB10000 because they sit at the low end of that weight range. The Anker 523 (PowerCore 10K) and similar banks weigh a bit more, but cost less and have a long, boring track record. Boring is what you want from a lithium battery in your pack.
Examples by use
The ultralight 10K
Best for: 3–4 day trips, every gram counted
- About 37 Wh, roughly 1.5–2 phone charges
- Look for USB-C in and out so one cable charges everything
- Carbon or slim aluminum shells save 30–50 g over budget plastic
The 20K workhorse
Best for: a week solo or a weekend for two
- About 74 Wh, roughly 3–4 phone charges
- Two outputs so two people charge overnight
- Pass-through charging lets it refill from a solar panel while it charges your phone
The laptop-class 27K
Best for: power outages, remote work, CPAP backup
- Just under the 100 Wh airline line, so it can still go in a carry-on
- 65 W+ USB-C PD charges a laptop or runs a router for a few hours
- The best "battery pack for a power outage" that still fits in a drawer
Expensive gear, honest reviews. Buy it once.
Power outage? Size it differently
For a short outage (a few hours to a day), one 20K–27K bank per person covers phones, a headlamp and a router. For outages that can last for days, a 200–500 Wh power station is better value per watt-hour. It also runs things a USB bank can't, like a CPAP, a small fan or a 12 V cooler. See our power station guide for the bigger units, and the emergency kit guide for what else goes in the bin.
Cold kills capacity
Lithium-ion cells deliver much less energy when cold, and you shouldn't charge them below freezing (0 °C / 32 °F). A bank that reads 50% at sunset can look empty at dawn. On winter trips, keep the bank and the phone in an inside pocket by day and in your sleeping bag at night. The capacity mostly returns once the cells warm up.
Solar for backpacking: be realistic
A folding 15–21 W panel rarely makes its rated output. Expect about half of the rating in good sun, and far less with clouds, forest shade or a panel swinging on your pack. Solar makes sense on long, exposed trips (desert, high alpine, rafting). For most trips under a week, a bigger bank is lighter and more reliable than a panel.
What owners say: Reddit and forum reports
We read owner threads on r/Ultralight, r/CampingGear, r/camping and r/WildernessBackpacking. These are patterns that came up again and again, not our own lab tests. Owners don't always agree, and where they split we say so.
10,000 mAh covers most weekends
- Ultralight hikers often say 10,000 mAh is enough for a phone over a 3–4 day trip with airplane mode on.
- The Nitecore NB10000 is the most-mentioned pick there, because it weighs about 150 g.
- Owners going a week or more without power, or sharing with a partner, step up to 20,000 mAh.
Sleep with it
- The most repeated cold-weather tip: keep the power bank and phone in your sleeping bag overnight.
- Owners report cold banks showing less charge and charging slowly, then recovering once warm.
Works on long, sunny trips only
- Owners who carry panels say they help on long trips with lots of sun, charging a power bank over a full day.
- For weekends, most say a bigger power bank is lighter and more reliable than a panel.
Threads we read (sample): Solar success with an NB10000 · Long-term solar review · Post-trip gear advice · What capacity do people carry? · Power banks in damp cold · Storing electronics in winter. Last checked October 17, 2026.
FAQ
Can I bring a power bank on a plane?+
Yes, in your carry-on only, never in checked bags. Under 100 Wh needs no approval. From 100 to 160 Wh you need airline approval, and above 160 Wh is not allowed. A 26,800 mAh bank is about 99 Wh, which is why that size is so common.
How many times will a 10,000 mAh power bank charge my phone?+
Usually about 1.5 to 2 times for a current smartphone. Rated capacity is measured at about 3.7 V, and conversion losses mean only about 60–70% reaches the phone.
What is the best power bank for a power outage?+
For a few hours to a day, a 20,000–27,000 mAh bank with 65 W+ USB-C keeps phones, a headlamp and a Wi-Fi router going. For outages that last days, or for medical devices, get a 200–500 Wh power station instead.
Is a power bank or a solar panel better for backpacking?+
For trips under about a week, a bigger power bank is usually lighter and more reliable. Small folding panels often give about half their rated watts in real conditions. They pay off on long, sunny, exposed trips.
How do I keep a power bank working in the cold?+
Keep it warm: an inside jacket pocket by day and your sleeping bag at night. Don't charge lithium cells below freezing. Most of the lost capacity returns once the bank warms up.
How many phone charges do I get from a 10,000 mAh power bank?+
About two full charges for most phones. A 10,000 mAh bank holds roughly 37 Wh, and about a third is lost to voltage conversion and heat, so you get far less than the mAh figure suggests.
Should I keep my power bank in my sleeping bag?+
On cold nights, yes. Lithium batteries deliver less when they're cold. Owners keep the power bank and phone in the sleeping bag or an inside pocket so they work in the morning.
Product purchase links are paused until exact models and retailer destinations are verified.
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