The Hong Kong Civil Aviation Department follows International Civil Aviation Organization standards and imposes clear restrictions on power bank specifications:

Rated Energy Limits:

≤ 100 Wh (watt-hours): No airline approval required; may be carried in carry-on baggage.
100 Wh to ≤ 160 Wh: Must obtain approval from the operating airline; typically used for large power banks for professional audio-visual equipment. Passengers are generally permitted to carry only two power banks within this specification.
> 160 Wh: Prohibited. Commonly found in large backup power sources (e.g., camping power stations).

How to calculate watt-hours (Wh)?
Most power banks directly label their rated energy (Wh). If only voltage (V) and milliampere-hours (mAh) are indicated, use the following formula:
Wh = (V) × (mAh / 1000)
Example: A power bank labeled 3.7V, 20000mAh.
Wh = 3.7V × (20000 / 1000) = 3.7V × 20 = 74 Wh (compliant)

Quantity Restrictions:

For power banks ≤ 100 Wh, carry only what is necessary for your personal journey. While there is no absolute upper limit, a reasonable quantity (e.g., 2-3 units) is recommended.
Final interpretation rests with the airline and security personnel. Carrying excessive quantities may still result in disposal requirements.

Pre-Departure Checklist:

- Verify Capacity: Check the label on the power bank to ensure its rated energy is below 100Wh. For power banks exceeding 100Wh but not exceeding 160Wh, contact the airline in advance to request approval.
- Carry-on Only: Never place power banks in checked baggage.
- Inspect Condition: Ensure the power bank shows no signs of swelling, cracking, or damage.

Traveling on Domestic Flights in China:

The Civil Aviation Administration of China prohibits passengers from carrying power banks without a 3C (CCC - China Compulsory Certification) label, with an illegible 3C label, or belonging to recalled models or batches on domestic flights.

Frequently Asked Questions (FAQ)
Q1: How many 10000mAh power banks can I bring?
A1: As long as each unit has a rated energy below 100Wh and the quantity is reasonable (e.g., 2-3 units), it's generally acceptable. A standard 10000mAh, 3.7V power bank is approximately 37Wh, well below the limit.

Q3: What if my power bank doesn't specify Wh?
A3: Look for voltage (V) and capacity (mAh or Ah), then calculate using the formula. If no specifications are provided or they are unclear, avoid carrying it to prevent confiscation during security screening.