How to Choose a Portable Battery (Power Bank)

Demystify the mAh and wattage numbers so you pick a power bank that actually charges your phone or laptop as fast as you expect.

4 min read · 6 steps · Checked April 2026

1. Step 1. Decide how much capacity you need

   For topping up a phone once or twice a day: 5,000-10,000 mAh (pocketable, light). For a long travel day or family with several phones: 20,000 mAh. For charging a laptop: 25,000 mAh or 100Wh. Remember, power banks themselves need recharging — figure on about 85% efficiency (a 10,000 mAh bank delivers about 8,500 mAh to your devices).

2. Step 2. Pick an output wattage that matches your fastest device

   For phone-only use: 18W is plenty. For iPad or tablet: 20-30W. For a MacBook Air or similar light laptop: 45-65W. For a bigger laptop: 100W. Look for the wattage on the output port (like "USB-C PD 65W"). Charging a 65W laptop with an 18W power bank will work slowly. But it is not a fast top-up.

3. Step 3. Check the ports

   A modern power bank should have at least one USB-C Power Delivery port — this is the fast, universal standard. USB-A ports are the older rectangular shape and are useful for older cables. Wireless (Qi) charging is handy but slower and less efficient. Two or more ports let you charge multiple devices at once, but shared wattage may slow each.

4. Step 4. Know the airline rules

   TSA and most airlines allow power banks in CARRY-ON only — never checked luggage. The limit is 100 Wh per battery (about 27,000 mAh at 3.7V). Most consumer power banks are well under this. Higher-capacity batteries (100-160 Wh) require airline approval. Anything over 160 Wh is banned on commercial flights entirely.

5. Step 5. Stick to trusted brands

   Recommended brands with solid safety records: Anker, UGREEN, Belkin, Mophie, and INIU. Avoid no-name Amazon brands with suspiciously high mAh claims and low prices — many exaggerate capacity and some are fire risks. A 20,000 mAh Anker is around $50 and lasts for years.

6. Step 6. Know when to replace it

   Lithium-ion batteries wear out — most power banks last about 500 full charge cycles, or 2-4 years of regular use, before capacity drops noticeably. If a power bank swells, gets hot, or stops holding a charge, stop using it. Many cities accept old power banks at electronics recycling centers — do not throw them in regular trash.