Power Bank Buying Guide (2027)

A power bank's milliamp-hour rating describes its internal cells, not the charge that reaches your phone. Conversion from the pack's 3.6V cells to a phone's 5V charging, plus heat, typically leaves about 60 to 70 percent of the rated capacity as delivered charge. That is why a 10,000mAh pack gives about two phone charges, a 20,000mAh pack about four, and a 5,000mAh pack about one. Compare packs by the maker's phone-charge claims, which already account for the loss, rather than by raw milliamp-hours alone.

Total wattage is the most misleading number on a power bank box. A pack can claim 200W while giving your laptop only 100W, or 100W while giving it only 65W once a second device plugs in. Always find the single-port figure for the port your device will use, and check the multi-port split, which makers publish in small print. For a laptop, match the single-port figure to the laptop's own charger wattage; for a phone, anything from 18W up charges at a good pace, and 30W to 45W covers the fastest phones.

A power bank is only as useful as its refill speed. A 20,000mAh pack at 100W input refills in under an hour, at 65W in under two hours, and at 18W in most of a day, and those three experiences feel like different products. Check the input wattage and the charger you own before buying: a fast pack on a slow charger is a slow pack, and a slow pack on a fast charger is still a slow pack. Travellers who use a pack daily should treat 30W input as the floor and 65W as the sweet spot.

USB-C cables are not all equal. A standard 3A cable caps power at 60W, so a 100W or 140W pack delivers only 60W through it, with no warning except a lower number on a display. Full laptop charging needs a 5A-rated cable, which some packs include and most do not. Built-in cables solve the forgotten-cable problem entirely, at the cost of short length and no replacement if one frays. Magnetic packs solve it differently, by removing the cable from the phone side, at the cost of wireless speed.

Wired charging is faster, cheaper per watt and universal. Magnetic charging is slower, iPhone-first and vastly more convenient on the move, since the pack snaps on one-handed and stays attached in a pocket. Qi2 at 15W narrows the gap, but wired at 30W still wins on time. The practical answer for many iPhone owners is both: a magnetic pack for the day and a wired pack for the bag, or a magnetic pack with a wired port for the moments when patience runs out.

Power banks fly in cabin baggage only, and the usual limit without airline approval is 100Wh. Every pack in this guide sits at or below 90Wh, so all of them fly without paperwork on most airlines, but checked baggage is off limits for all of them. On safety, buy packs with named protection systems and real certifications rather than the cheapest unbranded brick, since a lithium battery is the one gadget in your bag that deserves a brand you can find afterwards. Finally, remember that capacity fades: a pack kept for years will hold less than it did new, and a display that reads percentage honestly is worth more than a pack that pretends otherwise.