Rules below reflect the cabin-battery rules that apply to flights departing Hong Kong, and the equivalent limits used by Singapore (CAAS), the UK（CAA）and Australia（CASA）, which are aligned on the 100Wh threshold. Airline rules can be stricter than the regulator — always check your carrier before flying.
1. The three limits that matter
| Limit | Threshold | What happens |
|---|---|---|
| Carry-on only | All lithium power banks | Power banks may not go in checked baggage, on any of the four markets |
| Under 100Wh | Most phones, tablets, 10,000–27,000mAh banks | No approval needed, typically limited to 2 per person in Hong Kong |
| 100–160Wh | Large laptop banks | Airline approval required before boarding |
| Over 160Wh | Industrial packs | Not permitted in cabin or hold |
Hong Kong's Civil Aviation Department guidance also states power banks must not be used to charge devices during flight, and must not be left in an overhead bin unattended. The same practical rules apply at Changi, Heathrow and Australian airports.
2. Reading the label correctly
| Printed on the bank | What it means | Verdict |
|---|---|---|
| 10,000mAh, 3.7V | 37Wh | Cabin safe, no approval |
| 20,000mAh, 3.7V | 74Wh | Cabin safe, no approval |
| 27,000mAh, 3.7V | 99.9Wh | Right at the 100Wh ceiling — carry the label |
| 20,000mAh, 5V output rating | Do not use output voltage to compute Wh — use cell voltage 3.7V | Common mistake |
| No Wh printed | Ask the seller for the cell spec sheet | Risk of refusal at the gate |
The trap: some listings advertise "20,000mAh at 5V" to make the number look bigger. Watt-hours are calculated from the cell voltage (3.7V), not the USB output voltage. If a bank claims 20,000mAh and 100Wh, one of the two numbers is wrong.
3. Banks we stock
| Model | Price |
|---|---|
| MOMAX 1-World Airliner 防火袋 SR52｜流動電源袋 120×190mm [香港行貨] | 99 |
| MOMAX 1-Power Vital 10000mAh USB-A & USB-C Power Bank IP | 119 |
| MOMAX 1-Power Mini 5000mAh Compact 3-in-1 Power Bank IP1 | 129 |
| Thanko Neo 頸部冷卻器 [香港行貨] - 需加外置充電 | 159 |
| DIGIBAL DM10 X1 10,000mAh Qi2 Wireless Magnetic Power Ba | 159 |
| MOMAX 1-Power X Power Bank 10000mAh With Built-in USB-C | 159 |
| Momax 1-Power F.Pass+ 5000mAh 磁力帶線流動電源 (CCC 認證) IP157 [香 | 165 |
| BELKIN BoostCharge Power Bank 10K with Integrated Cable | 179 |
| BELKIN BoostCharge Power Bank 10K with Integrated Cable | 179 |
| BELKIN BoostCharge Power Bank 10K with Integrated Cable | 179 |
| BELKIN BoostCharge Power Bank 10K with Integrated Cable | 179 |
| MOMAX 1-Power Vital 20000mAh 流動電源 (CCC 認證)IP156 - 香港行貨 | 188 |
| SMARTCOBY PRO 30W PD 10000mAh 外置充電器 [香港行貨] | 198 |
| MOMAX 1-Power F.Pass⁺ 3000mAh Power Bank with Built-In C | 199 |
| MOMAX 1-Power Badge+ Emergency Power Bank With Find My L | 209 |
| XPOWER M10K 2合1鋁合金數顯10000mAh PD3.0+磁吸無線外置充電器 - 美國隊長系列 [香 | 219 |
| XPower M10K 3合1鋁合金數顯 10000mAh PD3.0+磁吸無線外置充電器[香港行貨] | 219 |
| MOMAX 1-Power X Pro Magnetic Wireless Power Bank with Bu | 219 |
| MOMAX 1-Power Vital+ 10000mAh Built-In Cable Power Bank | 219 |
| Momax 1-Power F.Pass+ 10000mAh 磁力帶線流動電源 (CCC 認證) IP158 [ | 229 |
| BELKIN BoostCharge 5K 纖薄磁吸流動電源 沙色 BPD010fqSA 香港行貨 | 229 |
| BELKIN BoostCharge 5K 纖薄磁吸流動電源 白色 BPD010fqWH 香港行貨 | 229 |
| BELKIN BoostCharge 5K 纖薄磁吸流動電源 黑色 BPD010fqBK 香港行貨 | 229 |
| MOMAX 1-Power Q.Pass 3000mAh Magnetic Power Bank IP115 [ | 229 |
| BELKIN BoostCharge 5K 磁吸無線流動電源連支架 粉紅色 BPD004qcPK [香港行貨] | 239 |
| BELKIN BoostCharge 5K 磁吸無線流動電源連支架 紫色 BPD004qcPU [香港行貨] | 239 |
4. Capacity vs what you actually get
| Rated capacity | Realistic phone charges | Notes |
|---|---|---|
| 5,000mAh | 0.8–1× | Pocket size, one top-up |
| 10,000mAh | 1.8–2.2× | The sweet spot for a day out |
| 20,000mAh | 3.5–4.5× | Heavy days, tablets, two devices |
| Above 20,000mAh | 5×+ | Airline paperwork above 100Wh |
Expect roughly 60–70% of the rated capacity to reach your phone. The rest is lost to voltage conversion and heat. A 10,000mAh bank that charges a 4,500mAh phone twice is performing normally, not under-delivering.
5. Charging speed: what the numbers mean
| Spec | Meaning |
|---|---|
| PD 20W | Fast charges most iPhones to about 50% in 30 minutes |
| PD 30W | Fast charges most Android flagships |
| PD 45W+ | Needed for tablets and small laptops |
| Qi2 15W | Magnetic wireless, aligns itself — no cable, but slower than wired |
| Pass-through | Can charge itself and a device at the same time; usually at reduced speed |
6. Shipping and compliance for SG, UK, AU
| Item | Singapore | United Kingdom | Australia |
|---|---|---|---|
| Delivery | 5–9 working days | 6–10 working days | 7–12 working days |
| Warranty | Return to Hong Kong | Same | Same |
| Cabin limit | 100Wh (2 per person typical) | 100Wh | 100Wh |
| Local certification | IMDA not required for passive banks | UKCA marking on mains chargers | RCM on mains chargers |
Power banks themselves are not radio devices, so they do not need IMDA registration in Singapore. Any mains charger bundled with one is a different matter — check for UKCA in the UK and RCM in Australia.
7. Common questions
Can I take a 20,000mAh bank on a plane?
Yes. At 3.7V that is 74Wh, below the 100Wh threshold. Carry it in the cabin, not checked baggage.
Two banks or one big one?
Two smaller banks are usually better: you stay under the per-person count limit and you still have power if one fails.
Can I charge my phone from a bank during a flight?
Hong Kong's civil aviation guidance prohibits using power banks to charge devices in flight. Check your airline — several carriers enforce this.
Do magnetic banks damage my phone?
No. Qi2 magnetic alignment is designed for phones with magnet arrays. It will not affect storage or the battery.
Why does my 20,000mAh bank only give 3 charges?
Conversion losses of 30–40% are normal. Rated capacity is measured at cell voltage, not at the USB port.
Is a cheap unbranded bank safe?
Treat unknown brands with caution — cell quality and protection circuitry are where cost is cut. A bank that runs hot is a bank to stop using.