Here’s a compact, practical guide to portable travel chargers (power banks) — what to buy, what to avoid, and what to know for flying.

Quick headline rules (air travel)

• Power banks must be carried in carry-on luggage only; they are not allowed in checked bags. (tsa.gov)
• Capacity rules (Watt‑hours, Wh): ≤100 Wh — allowed without airline approval; 100–160 Wh — allowed in carry‑on only with airline approval (usually max 2 units); >160 Wh — prohibited. Always check the bank’s Wh rating (or calculate it). (tsa.gov)
• Note: airlines and regulators have been increasing scrutiny of lithium batteries; some carriers have additional restrictions (so check your airline before flying). (businessinsider.com)

How to read capacity (mAh → Wh)

• Wh = (mAh × Voltage) ÷ 1000. Most power banks use 3.7V internal cells. Example: 20,000 mAh → 20,000 × 3.7 ÷ 1000 ≈ 74 Wh. If the label shows Wh, use that; if only mAh is listed, convert. (batteryskills.com)

What to look for when buying

• Capacity (mAh/Wh): match to your use-case (see quick guide below). If you plan to fly, keep under 100 Wh unless you get airline approval. (tsa.gov)
• Power delivery (PD) & wattage: for phones/tablets, 18–30W PD is plenty; for laptops you’ll likely need 45–100W PD (check your laptop’s USB‑C charging spec). High-watt PD (60–140W) is needed for many full‑size laptops.
• Ports: USB‑C (PD) is essential; extra USB‑A ports are useful for older devices. Multiport chargers let you charge a phone + laptop simultaneously.
• Size/weight vs. capacity: bigger mAh = heavier. Decide between pocket-size convenience and multi-day backup.
• Pass‑through charging: useful (charges bank while it charges devices) but slightly increases heat and complexity—look for reputable brands if you need it.
• Safety: choose banks with over‑current, over‑charge, short‑circuit protection and from reputable brands (Anker, Belkin, RavPower, Zendure, etc.). Avoid no‑name imports without safety markings.
• Labeling: choose chargers with clear Wh or mAh + voltage info (helps at airport security).

Quick capacity guide (typical real‑world estimates)

• 5,000 mAh (~18–20 Wh): pocketable; ~1 full phone charge (small phones).
• 10,000 mAh (~37 Wh): good day‑trip pack; 1–2 full phone charges or partial tablet.
• 20,000 mAh (~74 Wh): multi‑day phone backup or 1 laptop top‑up (depends on laptop). Still under 100 Wh for flying. (batteryskills.com)
• 30,000 mAh+ (≈111 Wh and up): great for heavy use, but once over ~100 Wh you’ll need airline approval and >160 Wh is banned on planes — so not ideal for typical air travel. (tsa.gov)

Practical packing and travel tips

• Keep power banks in your carry‑on, with terminals protected (tape or original case) and labels visible. (tsa.gov)
• If a device doesn’t list Wh, calculate it (see formula above) and carry proof (photo of label/spec) if you expect inspection. (batteryskills.com)
• If traveling internationally, check both airline and destination airport rules — some carriers now restrict in‑flight use or require visible placement. (businessinsider.com)
• Avoid leaving power banks fully discharged or exposed to high heat; store at ~30–50% charge for long trips.

If you want, I can:

• Recommend specific models in three categories (pocket 5–10k, travel 10–20k, laptop 45–100W PD) that match your device and airline needs.
• Help convert mAh values for a specific power bank you’re considering (tell me the mAh and voltage listed).

Which would you like?