Decision Lantern

Energy and power calculator

What size power bank do I need for a trip?

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Travelers estimating a pack from device energy and the number of recharges. The decision this page isolates is narrow on purpose: convert device watt-hours and needed charges into a pack category. Watt-hours and inverter watts are different limits. Size both before you compare a station.

Trip charging need

Pack category to compare

20–40 Wh everyday pack

38 Wh usable floor

About 10,271 mAh at 3.7 V

Example products for What size power bank do I need for a trip?

Real products that fit this planning category. Specs come from the manufacturer’s product page. These are examples, not rankings.

Check everyday examples on Amazon

Compare the official examples

The table below is a side-by-side of the official examples on this page. Columns are published facts—maker, planning class, and notes taken from the official page—not scores. Anker 737 Power Bank, Anker Prime 20,000 mAh, and Nitecore NB20000 are included so you can see how classes differ, then open the official page for the current specification.

Published facts for the example products on this page. Not a ranking.
ExampleMakerPlanning classesPublished notes
Anker 737 Power BankAnker20–40, 60–100, Pocket, Laptop, High Capacity140 W; 24000 mAh class
Anker Prime 20,000 mAhAnker20–40, Everyday, Pocket20000 mAh; USB-C PD
Nitecore NB20000Nitecore20–40, Everyday, LaptopTravel-weight pack; USB-C

What to verify before you buy

Measurement notes

Measure: Read the watt-hour number on the bank or convert milliamp-hours at 3.7 V: 20,000 mAh is about 74 Wh. Count full charges you need, not “days away.” Airline cabin limits are 100 Wh without airline approval.

Example: A 12 Wh phone charged twice and a 50 Wh laptop charged once is 74 Wh of demand before conversion loss. A 20,000 mAh bank covers the phones; the laptop needs a 60–99 Wh USB-C PD pack.

Avoid: Buying by milliamp-hours printed at 5 V. Brands inflate that number. Compare watt-hours, and stay under 100 Wh if you need to board without asking the airline.

How this estimate works

Multiply device watt-hours by the number of full charges, divide by conversion efficiency, and convert the result to milliamp-hours at 3.7 V.

Know the limits

  • Cable loss, cold weather, and laptop USB-C negotiation reduce delivered energy.
  • Airline watt-hour limits for carry-on batteries are separate from this sizing estimate.
  • Manufacturer capacity labels are often stated at the cell voltage, not the USB output.

Frequently asked questions

How does the power bank trip work?

It converts the published inputs on this page into a planning class using a published rule. Multiply device watt-hours by the number of full charges, divide by conversion efficiency, and convert the result to milliamp-hours at 3.7 V. The headline is a class such as 20–40, 60–100, Pocket, Laptop, High Capacity, and Everyday, not a vendor ranking.

Is Anker 737 Power Bank better than Anker Prime 20,000 mAh?

This page does not rank Anker 737 Power Bank, Anker Prime 20,000 mAh, and Nitecore NB20000. Anker 737 Power Bank and Anker Prime 20,000 mAh are listed because they are real products with official pages that map to different or overlapping classes. The useful question is which class matches your inputs.

Do the product links earn Decision Lantern a commission?

Yes, when a product name or “View on Amazon” link goes to Amazon. Those are associate links. Decision Lantern may earn a commission at no extra cost to you. Official manufacturer pages are separate and are not tagged.

Sources

  1. Basics of Electricity, Energy, National Renewable Energy Laboratory. Retrieved .

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