A travel power bank is one of the highest-value items in your bag — but before you shop, know the one rule that matters at the airport: a power bank must go in your carry-on, never in checked luggage. It holds a lithium battery, and those aren't allowed in the hold. Beyond that, the best travel power bank comes down to capacity, airline limits, charging speed and weight. Here's how to weigh them.
1. Carry-on only — and why
Lithium batteries can, in rare cases, overheat, and a fire in an inaccessible cargo hold is far more dangerous than one in the cabin where crew can respond. For that reason, spare lithium batteries and power banks are restricted to carry-on baggage on essentially all airlines.
- Always pack power banks in the cabin — never in a checked bag.
- Keep them accessible and protect the terminals so they can't short against keys or coins.
- Rules and limits vary by airline and change — check your airline and the current aviation guidance before you fly. See our power banks on flights guide for the details.
2. mAh vs Wh — and why airlines care
Capacity is usually advertised in mAh (milliamp-hours), but airlines regulate by Wh (watt-hours), because Wh reflects the actual energy stored regardless of voltage. Roughly, Wh = (mAh ÷ 1000) × voltage, and most power bank cells are around 3.6–3.7V. Many banks print the Wh figure on the casing.
| Term | What it tells you |
|---|---|
| mAh | Marketing capacity figure. Bigger number, more charges — but not directly comparable across voltages. |
| Wh (watt-hours) | True energy stored, and what airlines limit. Higher-capacity banks may be capped or need airline approval. |
Airlines commonly set tiers where banks under a certain Wh are fine, a higher band may need approval, and above that they're not permitted — but the exact thresholds vary, so check your airline's current limit rather than assuming.
3. How much capacity do you actually need?
Think in phone charges. A modern phone battery is often somewhere around 3,000–5,000 mAh, and real-world losses mean a power bank delivers less than its printed capacity. A rough planning guide:
- ~5,000 mAh: pocketable, roughly one phone top-up — good for a day out or a light backup.
- ~10,000 mAh: the travel sweet spot for most people — a couple of full phone charges in a still-portable size.
- ~20,000 mAh and up: multiple devices or a laptop top-up, at the cost of more weight and closer attention to airline Wh limits.
Treat these as estimates — actual charges depend on your phone, cable and conditions.
4. Charging speed, ports and weight
Once capacity is sorted, the features that shape day-to-day use:
- USB-C with Power Delivery (PD): the modern standard — faster charging and, at higher wattages, enough to run many laptops.
- Fast charging support matters most if you're topping up quickly between activities; match it to what your devices accept.
- Pass-through charging (charging the bank while it charges your device) is convenient but not universal — check the spec if you want it.
- Weight and size: capacity costs grams. For carry-on travel, the lightest bank that meets your needs beats the biggest one you'll leave in the hotel.
Planning your tech kit? See the travel packing list, and if you use a bag finder, our luggage tracker guide covers those too.