Understanding the 100Wh Limit: Why 20000mAh Meets TSA Regulations

Updated 2026-09-29 · Power Bank Guide

20000mAh 100Wh TSA limit explained

The 20000mAh 100Wh TSA limit explained starts with a simple math fact: 20000mAh at the battery’s nominal 3.7V equals about 74Wh. That is comfortably below the TSA’s 100Wh carry‑on ceiling, so you can bring a 20000mAh power bank on most flights without a special declaration. It’s the same logic that lets a 100Wh USB‑C charger fly, but the higher milliamp‑hour rating gives you a larger usable capacity.

What 20000mAh really means

Milliamp‑hour (mAh) is a measure of charge storage at a nominal cell voltage of 3.7V. To convert to watt‑hours (Wh) you multiply by that voltage and divide by 1000:
Wh = (mAh ÷ 1000) × 3.7V.
So 20000mAh × 3.7V ÷ 1000 = 74Wh. Most manufacturers round the mAh rating up for marketing, so the real capacity is often 10–15% lower. A 20000mAh power bank usually delivers around 60–70% of its stated Wh to your phone, because of conversion loss, internal resistance, and the fact that devices don’t use the entire 3.7V range.

Real‑world capacity and how many charges you get

Let’s break it down for common phones:

• iPhone 17 (battery ~4000mAh, 12.3Wh) – 3–4 full charges from a 20000mAh bank.
• Samsung Galaxy S23 (battery ~5000mAh, 15.4Wh) – 2–3 full charges.
• Xiaomi Mi 12 (battery ~5000mAh, 15Wh) – 2–3 full charges.
• Google Pixel 8 (battery ~5000mAh, 15.4Wh) – 2–3 full charges.

These numbers assume the device draws its rated 4.5–5V output and you’re using a USB‑C PD or QC cable. If you use a lower‑power USB‑A output, the count drops slightly due to higher resistance and lower voltage.

Output wattage and 22.5W fast charging

Modern power banks expose USB‑C Power Delivery (PD) ports that can deliver up to 100W, but most 20000mAh models top out at 22.5W. That means they can output 5V at 4.5A or 9V at 2.5A. For a typical smartphone, 22.5W is fast enough to top a battery from 0 % to 80 % in about 30–45 minutes, depending on the device’s own charging protocol.

The INIU 20000mAh Portable Charger is a great example of a 22.5W flight‑safe bank. It’s pocket‑sized, includes a USB‑C cable and a small flashlight, and can recharge an iPhone 17, Samsung, Xiaomi or Google phone multiple times while staying under the 100Wh limit.

Power bank specs explained: capacity, specs & speed

When shopping, compare:

1. Capacity (mAh/Wh) – higher is better, but check real‑world efficiency.
2. Output ports & wattage – 22.5W is a sweet spot for most phones; 45W or 60W is needed for laptops.
3. Input rate – how fast the bank recharges itself (e.g., 18W or 30W).
4. Build quality & certifications – look for over‑current protection, temperature control, and, for travel, a 100Wh or lower rating.

Choosing a 20000mAh, 22.5W bank like the INIU means you get a balance of capacity, speed, and travel compliance without the bulk of a 30000mAh model.

FAQ

What is the difference between mAh and Wh?

mAh measures charge at a nominal 3.7V, while Wh measures actual energy (charge × voltage). To compare batteries of different voltages, use Wh.

Can I use a 20000mAh bank on a commercial flight?

Yes, as long as it stays under 100Wh. Confirm with your airline’s policy before traveling, because some carriers have stricter limits or require a declaration.

How fast will my phone charge with a 22.5W output?

Typical 5V/4.5A output will bring most smartphones from 0 % to 80 % in 30–45 minutes. Exact time depends on the device’s charging protocol and current battery level.