The first number most people look at when buying a power bank is the mAh capacity rating, but that figure alone does not tell the whole story. A 10,000mAh power bank can theoretically charge a phone twice, yet due to voltage conversion loss you typically get only about 70-80% of that rated energy in real use.
Just as important as capacity is the output wattage. A power bank rated at 10W will charge a phone slowly, while a Power Delivery model with 20-30W output can charge the same phone in a fraction of the time. If you plan to charge a tablet or laptop, look for at least 45W of output.
Pass-through charging, the ability to charge the power bank itself while it charges another device, is a genuinely useful feature for travelers. Multiple ports also matter if you regularly need to charge more than one device at the same time.
On the safety side, look for CE certification along with overcurrent, short-circuit and overheat protection. Cheap, uncertified power banks often skip these safeguards, which creates real risk for both the device and the user.
Finally, balance portability against capacity: a roughly 10,000mAh model fits comfortably in a pocket for daily use, while anything above 20,000mAh makes more sense for longer trips. Charjett's range of power bank capacities is built around making that trade-off easy depending on how you actually use it.