I bought a cheap power bank from a drugstore checkout line once. It charged my phone to about forty percent before dying. The next time I needed it — at an airport, naturally — it had discharged completely just sitting in my bag for two months. I threw it away and decided to figure out what actually matters in a portable charger.

After testing a handful of popular models and reading far too many spec sheets, here’s what separates the ones worth buying from the junk.

Understanding capacity (and why the number on the box lies)

A 10,000 mAh power bank does not deliver 10,000 mAh to your phone. The actual usable capacity is about sixty to seventy percent of what’s advertised due to voltage conversion losses and heat. A 10,000 mAh bank will charge a typical phone (around 4,000 mAh battery) about one and a half times.

For a full day away from outlets with heavy phone use — navigation, photos, streaming — get at least 20,000 mAh. That’ll give you three to four full charges realistically.

The specs that actually matter

USB-C Power Delivery (PD): This is the one that charges your phone fast. A charger with PD can take an iPhone from zero to fifty percent in about thirty minutes. If the charger doesn’t list PD or Quick Charge in the specs, it’s going to charge slowly. Like, three hours to fill your phone slowly.

Pass-through charging: This lets you charge the power bank while it charges your phone. Useful at hotels with one outlet. Not every model supports this.

Weight vs capacity: A 20,000 mAh bank weighs about twelve to fourteen ounces — roughly the same as a can of soda. Anything significantly lighter at that capacity claim is lying about its capacity.

Recommendations at different price points

Budget ($20-30): Anker PowerCore 10,000 mAh. Reliable, compact, charges at standard speed. Not the fastest but Anker’s quality control is consistently good and their customer service actually responds. One full phone charge, maybe a bit more.

Mid-range ($40-50): Anker 533 Power Bank (10,000 mAh) or the INIU 20,000 mAh with PD. Both support fast charging. The INIU gives you more capacity for the money and includes a built-in USB-C cable, which is one fewer thing to forget.

Premium ($60+): Anker PowerCore 24K or the UGREEN 25,000 mAh 145W. These charge laptops as well as phones — the UGREEN can power a MacBook at full speed. Overkill if you just need phone charging, but if you travel with a laptop and a tablet, it replaces three separate chargers.