How to Choose the Right Power Bank
What mAh really means, how many phone charges you actually get, and which output and size suits your use.
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How much capacity do you need?
Phone batteries are roughly 3,000–5,000mAh. Conversion losses mean you get less out of a power bank than the number on the box, so a realistic guide is:
- 5,000mAh — roughly one full phone charge. Pocketable, good as an emergency top-up.
- 10,000mAh — roughly two charges. The best all-round size for most people.
- 20,000mAh — roughly three to four charges, or a phone plus a tablet. Heavier, better for travel and festivals.
See the power banks category for each size.
Output matters as much as capacity
Capacity decides how many charges. Output decides how fast each one is. A power bank with USB-C Power Delivery output will refill a modern phone far faster than an old 5W USB-A pack of the same capacity. Check the output figure, not just the mAh.
Input matters too: a USB-C input means the power bank recharges quickly with the same cable you already carry.
Magnetic and wireless power banks
A magnetic pack snaps to the back of a compatible iPhone and charges without a cable, which is genuinely convenient while walking around. Wireless charging is less efficient than cable charging, so you get fewer charges from the same capacity — a trade of efficiency for convenience.
Size, weight and travel
A slim 10,000mAh pack fits a jacket pocket; a 20,000mAh one is noticeably heavier in a bag. For flights, power banks must travel in hand luggage, never in checked bags, and airlines set limits based on watt-hours. Check your airline’s rules before you fly.
Practical points people miss
- Charge a new power bank fully before first use.
- Top it up every couple of months even when unused.
- Keep it out of a hot car.
- Carry the right cable — a power bank is useless without it.
- Check whether it can charge and be charged at the same time if you need pass-through.
Questions
Voltage conversion loses energy, and the phone itself uses power while charging. Expect roughly 60–75% of the stated capacity to reach your phone.
In hand luggage, yes, within your airline's watt-hour limits. They are not permitted in checked baggage.
No. Speed comes from the output rating and the cable, not the capacity.
Shop the range. Everything mentioned here is in our full accessories range, with GBP pricing and compatibility listed on every product page. Questions about your model? Email or call us.