Quick guide to portable power banks — what to buy, how to use them safely, and travel rules.

1. Quick overview

• A power bank’s usable energy is best measured in watt‑hours (Wh). Many sellers list milliamp‑hours (mAh); converting between them needs the battery voltage (typical Li‑ion cells ≈ 3.6–3.7 V). Formula: Wh = (mAh × V) / 1000. (anker.com)

2. Choose capacity by need (practical examples)

• 5,000–10,000 mAh (≈18–37 Wh at 3.7 V): pocketable — good for 1–2 phone charges.
• 20,000 mAh (≈74 Wh at 3.7 V): multi‑charge for phones, a tablet once, small travel use.
• 40,000+ mAh / power stations (100+ Wh): can run laptops, cameras, or small appliances (look for AC outlets and higher Wh).
  Note: for high‑power devices, check Wh (not only mAh) and the output wattage the bank can supply.

3. Important specs to check

• Watt output and ports: USB‑C PD (Power Delivery) ratings matter (e.g., 20W, 45W, 65W, 100W+). Higher W required for fast charging and laptops. USB‑PD has been extended up to 240W (USB‑PD 3.1 / EPR) for very high‑power devices. (usb.org)
• PD vs PPS: PPS (programmable power supply) helps phones charge more efficiently/colder — useful for Samsung/Pixel devices. (Look for PD + PPS support in specs.) (usb.org)
• Ports & simultaneous charging: check if the bank can deliver full wattage to one device or splits between ports.
• AC outlet vs USB only: AC outlets let you run non‑USB devices but increase size/weight.
• Recharging speed: consider how fast the bank itself charges and whether it supports pass‑through (charging the bank while it charges devices — not recommended for safety by some manufacturers).
• Weight/size: higher Wh → heavier and bulkier.

4. Safety & certifications (very important)

• Look for recognized safety testing/certifications (UL/ETL, ANSI/CAN/UL 2056 is a recent dedicated standard for power banks, UL/other battery safety standards and UN38.3 for transport testing are good signs). Certified products (UL mark, reputable labs) are safer than no‑name, uncertified units. (ul.com)
• Be cautious of low‑cost, no‑name power banks — CPSC has issued safety warnings and recalls for some models that overheated or ignited. If you buy used/cheap, verify model and check recalls. (cpsc.gov)

5. Air travel rules (U.S. — carry‑on vs checked baggage)

• U.S. rules: lithium‑ion batteries/power banks are allowed in carry‑on. Batteries up to 100 Wh are allowed without airline approval. Batteries 101–160 Wh require airline approval (limit: up to two spare batteries in carry‑on). Batteries >160 Wh are generally forbidden as carry‑on/spare. Spare batteries/power banks are not allowed in checked baggage. Always carry power banks in carry‑on and protect terminals from shorting. (faa.gov)
• Airlines may add extra restrictions (for example, some carriers have started requiring power banks to be visible / forbidding charging in stowed baggage or otherwise tightening rules). Check your airline’s policy before flying. (reuters.com)

6. Safety & use tips

• Inspect before each use: don’t use if swollen, leaking, hot, damaged, or if it emits smoke. Stop using and follow safe disposal guidance. (cpsc.gov)
• Charge on non‑flammable surfaces and avoid charging overnight under pillows or on beds. Don’t leave charging power banks unattended for long periods. (productsafety.gov.au)
• Don’t store in extreme heat (cars in summer) or in direct sunlight.
• Avoid cheap unbranded cables; use rated USB‑C cables for PD and high current (E‑marked/5A cable for >60W/100W where required). (act-connectivity.com)
• Disposal: don’t toss Li‑ion power banks in household trash or curbside recycling. Follow local hazardous waste / battery recycling rules (CPSC and local HHW guidance). (cpsc.gov)

7. Recommendations by use case (what to look for)

• Occasional phone user / travel: 10–20,000 mAh, USB‑C PD 20–30W, lightweight.
• Power user / tablet + phone: 20–30,000 mAh, USB‑C PD 45–65W (for faster phone/tablet and small laptops).
• Laptop & multi‑device or remote work: look for 65–150W USB‑C PD output and 50–100 Wh+ (note airline limits if you travel). For full desktop replacement or to run non‑USB devices, get a portable power station (AC outlet) with Wh matching your needs.
• Long trips / camping: higher Wh portable power stations with AC outlets and multiple ports.

8. Final checklist before buying

• Wh (or convert mAh→Wh using voltage), max output wattage, PD/PPS support, number/type of ports, recharge time, weight, safety certifications (UL/ETL/ANSI/CAN/UL 2056 or equivalent), user reviews and known recalls, airline travel compliance if you fly. (anker.com)

If you want, I can:

• Suggest specific models in different price ranges (I’ll check current availability and up‑to‑date reviews), or
• Help convert a specific power bank’s mAh rating into Wh and tell you whether it’s airline‑legal.