Alan
What to look for in a power bank
A power bank is only as good as the energy it actually delivers. Makers quote big capacity numbers, but conversion losses mean you get noticeably less than the label, and the figure that matters at the gate is watt-hours, not milliamp-hours. Three things decide whether a bank suits you: how much usable energy it holds, how fast it can push that energy out, and whether it is cleared for your flight. Here is what each one means in plain English.
Capacity and usable power
The mAh on the label is the raw cell capacity, not what reaches your phone. After the step-up from 3.7V to 5V or more, you get roughly 60 to 70% of it. A 10,000mAh bank delivers around 6,000 to 6,500mAh to your device.
Output speed
Capacity is how much; output wattage is how fast. A 20W bank tops up a phone nicely, but a laptop needs 60W or more from a USB-C port. Check the output figure, not just the capacity, or you may end up trickling a laptop all day.
Airline rules
Airlines measure power banks in watt-hours. The cabin limit is 100Wh without approval, about 27,000mAh, and a bank must travel in your carry-on, never in checked luggage. Most everyday banks are well under the limit.
Why capacity is not the whole story
The headline mAh number sells power banks, but on its own it tells you very little. Three quick truths save most buyers from a poor choice:
Usable energy is lower than the label. Expect 60 to 70% of the rated mAh to reach your device after conversion losses.
Flights care about watt-hours. Convert with mAh times 3.7 divided by 1000. So 20,000mAh is about 74Wh, comfortably under the 100Wh cabin limit.
Output decides what it can charge. 20W for phones, 45W for tablets and fast phones, 60W and up for laptops.
Find your power bank in one step
Tell us how you charge and we will point you to the right review.
Everyday top-ups
I just need to top up my phone
A pocket-sized 10,000mAh bank for a phone and earbuds, around two full charges.
Laptop power
I need to charge a laptop
High-capacity banks with 60W or more output for a full working day away from a socket.
Wireless and MagSafe
I want magnetic wireless charging
A Qi2 magnetic bank that snaps to an iPhone, fastest on the iPhone 16 and 17.
Flying soon
I want to know what I can fly with
The 2026 cabin rules for the UK, EU and US, and how to pack a power bank safely.
Power banks we have reviewed, compared
The key numbers side by side. Scores are our own, based on independent lab data and named third-party testing.
| Power bank | Capacity | Output | Airline | Best for | Score | Review |
|---|---|---|---|---|---|---|
| Anker Nano 10K | 10,000mAh (36Wh) | 45W | 36Wh, carry-on | Everyday phone carry | 8.8 | Read › |
| UGREEN MagFlow | 10,000mAh (36Wh) | Qi2 25W wireless, 30W wired | 36Wh, carry-on | iPhone wireless charging | 8.5 | Read › |
| Anker 737 | 24,000mAh (86Wh) | 140W | 86Wh, carry-on | High-power laptop travel | 6.8 | Read › |
| Anker A1695 | 25,000mAh (90Wh) | Up to 165W | 90Wh, carry-on | Laptop and cable convenience | 8.5 | Read › |
Capacities are manufacturer rated; usable output is lower after conversion losses. Watt-hour figures are what airlines use for the 100Wh cabin limit. Figures cross-checked against named third-party testing in each review.
Power bank questions, answered
The things buyers ask us most about power banks, explained in plain English.
How many mAh do I need?
For phone top-ups, 10,000mAh covers a full day and around two charges. For multi-day trips, or to charge a laptop, look at 20,000mAh or more. Remember you get roughly 60 to 70% of the rated number in usable power.
Why don’t I get the full mAh from a power bank?
Conversion losses. The cells store energy at 3.7V, but your device charges at 5V or higher, and that step-up wastes 30 to 40%. So a 10,000mAh bank delivers around 6,000 to 6,500mAh to your phone, not the full label figure.
How many times will a 10,000mAh power bank charge my phone?
Around 1.5 to 2 full charges of a modern phone, depending on the model. A large iPhone Pro Max or Galaxy Ultra is closer to 1.2 charges, a smaller phone closer to 2. Wireless charging gives fewer charges than a cable.
Can I take a power bank on a plane?
Yes, in your carry-on, never in checked luggage, and it must be 100Wh or under, about 27,000mAh. Most everyday banks qualify easily. Rules tightened on some airlines in 2026, so check the details in our full guide before you fly.
What is Wh and the 100Wh airline rule?
Watt-hours measure total stored energy, and airlines allow up to 100Wh in the cabin without approval. Convert milliamp-hours to watt-hours with mAh times 3.7 divided by 1000. So 20,000mAh is about 74Wh, and 27,000mAh is about 100Wh.
Can a power bank charge a laptop?
Yes, if it has a USB-C port rated 60W or more and enough capacity, ideally 20,000mAh and up. A small 20W bank will only trickle a laptop and may not keep up under load. Check the output wattage, not just the capacity.
Do power banks lose charge when they are not used?
Yes, slowly, around 2 to 10% a month through natural self-discharge. A bigger drain is leaving the digital display switched on, which can cost around 15% in a day on some banks. Press the button to turn the screen off when you are not reading it.
What is Qi2 and MagSafe wireless charging?
Magnetic wireless charging that snaps to the back of a phone. Qi2 tops out at 15W on most phones and 25W on the newest iPhones. It is convenient and cable-free, but slower and warmer than a wired connection, so a cable is still faster.
How we choose what to recommend
We do not run a battery lab, and we will never pretend we did. What we do is read the evidence properly and explain it in plain English, so you can buy with confidence.
We start with the specs. Manufacturer data and the real Amazon listing, checked for the exact model, capacity and watt-hours.
We cross-check the labs. Independent measurements from named sources such as Macworld, iMore, TechRadar and Cult of Mac.
We weigh real owners. Verified buyer feedback to catch what spec sheets leave out, like heat or display drain.Every figure in our reviews is attributed to its source, and we flag anything not yet independently verified. That is how an independent site earns trust without owning every product.
Curated by Alan, a network engineer with nine years in the industry. Reviews are kept current and dated. Last reviewed June 2026.
