Here’s a practical, all-in-one guide to portable chargers (power banks) so you can pick the right one and use it safely.

Quick summary

• “Portable charger / power bank” types: small pocket banks (5k–12k mAh), travel/work banks (20k–30k mAh), high‑capacity power stations (100 Wh+), wireless/MagSafe banks, and specialty banks (jump starters, 100W+ laptop banks).
• Key specs to check: capacity (mAh and Wh), output power (watts), ports & protocols (USB‑C/PD, PPS, QC), physical size/weight, and safety/certifications.
• Airline rules: spare power banks are carry‑on only and there are watt‑hour limits—see FAA/TSA guidance below. (faa.gov)

1. Capacity: what mAh and Wh mean (and how to compare)

• mAh (milliamp‑hours) is a cell capacity number that brands commonly show. Watt‑hours (Wh) measure stored energy and are more useful for comparing batteries of different voltages. Conversion: Wh = (mAh × V) / 1000 (most lithium cells use ~3.6–3.7 V as the internal nominal voltage). Example: 10,000 mAh × 3.7 V ÷ 1000 ≈ 37 Wh. (anker.com)
• Real‑world usable energy is lower than the rated internal mAh because of voltage conversion and losses (heat, electronics). Expect roughly ~70–90% of rated energy delivered to your device depending on quality and output power. That’s why a 10,000 mAh bank often gives ~1.5–2.5 full smartphone charges in practice. (techradar.com)

2. Output power (how fast it charges)

• Power = volts × amps (watts). For charging speed, look at watt (W) ratings (e.g., 18W, 30W, 45W, 65W, 100W).
• USB Power Delivery (USB‑PD) is the modern standard for negotiating higher voltages and currents (PD 3.1 supports up to 240 W for devices that support it). USB‑C PD is what you want for fast phone charging and laptop charging capability. (usb.org)
• Quick practical guidance:
  • Phone top‑ups / daily carry: 18–30 W PD is plenty for fast charging.
  • Powering/charging laptops: choose banks with 45 W+ (light laptops) or 65–100 W for mainstream laptops; specialty 140–240 W solutions exist for high‑power devices (if supported).
  • Multi‑device use: multi‑port banks with PD on a USB‑C port + USB‑A for accessories.

3. Ports & features to look for

• USB‑C PD (preferably PD 3.0/3.1) — best single‑cable fast charging.
• PPS (programmable power supply) for better thermal/faster charging with some Android phones.
• Pass‑through charging if you want to charge the bank and devices at the same time (note: not all banks support it safely).
• Digital display or LED indicators for remaining capacity.
• Wireless (Qi) or MagSafe if you want cable‑free phone charging — expect slower charging and extra loss vs wired.

4. Safety & build quality

• Look for over‑current, short‑circuit, over‑temperature protection and safety certifications (UL, CE, FCC or local equivalents).
• Quality cells (Samsung/LG/Panasonic) and a known brand typically give better reliability and safer behavior.
• Avoid very cheap unlabeled power banks that lack protection circuits.

5. Travel and airline rules (important)

• Most U.S. and international airline/aviation rules require spare lithium batteries and power banks to be carried in the cabin (carry‑on) only. Lithium batteries are commonly limited to 100 Wh or less per battery. With airline approval you may carry up to two spare batteries of 101–160 Wh; batteries >160 Wh are generally prohibited. Always check your airline’s current rules before flying. (faa.gov)

6. Picking the right size by use case (no brand names)

• Commuter / pocket: 5,000–10,000 mAh; 18–30 W PD; very portable.
• Traveler / multi‑day: 20,000–30,000 mAh; 30–65 W PD; multiple ports.
• Laptop + phone: 20,000–40,000 mAh with 65–100 W USB‑C PD (check laptop power draw).
• Emergency / home backup: look at “power stations” rated in Wh (200 Wh / 500 Wh etc.) that include AC outlets.
• Wireless / convenience: 5k–10k mAh with Qi or MagSafe, but expect somewhat lower efficiency.

7. Practical tips & maintenance

• Carry a short USB‑C to USB‑C cable (good cables reduce losses).
• Store partially charged (around 40–60%) if you’ll keep a bank long‑term; avoid extreme heat.
• Replace older power banks if capacity or behavior changes noticeably.
• If you need to charge while on a plane, check airline policy — some carriers now ban charging power banks while stowed or require power banks to be visible/in use in the cabin (policies vary by carrier). (faa.gov)

If you want, I can:

• Suggest specific models in a price range