Every guide on GadgetWorldNews follows the same checklist. This page explains what we look at, which numbers we calculate ourselves, and where the limits of our method are — so you can judge our conclusions instead of taking them on trust.
1. Capacity: From mAh to What Your Phone Actually Gets
Power banks are rated at the voltage of their internal cells (3.6–3.85 V), while phones are charged at 5 V or higher. That conversion, plus heat and cable losses, means a power bank delivers roughly 60–70% of its printed mAh to your device. We always convert capacity to watt-hours (Wh = mAh × V ÷ 1000), because Wh is the number that stays honest across devices and the one airlines use.
| Printed capacity | Energy (at 3.7 V) | Usable for a phone (approx.) | Typical full phone charges* |
|---|---|---|---|
| 10,000 mAh | 37 Wh | 6,000–6,500 mAh | about 1.5 |
| 20,000 mAh | 74 Wh | 12,000–13,000 mAh | about 3 |
| 26,800 mAh | 99 Wh | 16,000–17,500 mAh | about 4 |
| 30,000 mAh | 111 Wh | 18,000–19,500 mAh | over the 100 Wh airline limit |
*For a phone with a ~4,000 mAh battery. Larger phones and tablets get proportionally fewer charges.
2. Charging Standards and Real Speed
A label like “65W” says nothing about which device can use it. We check which protocols a product supports — USB-C Power Delivery (PD), PPS for Samsung Super Fast Charging, Qualcomm Quick Charge — and which output profiles each port offers (for example 5 V/3 A, 9 V/3 A, 20 V/3.25 A). Then we match that against what common phones, tablets and laptops request.
- whether the advertised wattage is per port or shared between ports
- whether a laptop can charge, or only slow down its battery drain
- pass-through charging: can the power bank charge itself and a device at the same time
- recharge time of the power bank itself and the input wattage it needs
3. Safety and Build
We look for certified cell chemistry (Li-ion, Li-polymer or LiFePO4), the protections the manufacturer lists (over-charge, over-discharge, short circuit, temperature), and the warning signs buyers report most often: swelling, heat during fast charging and capacity that drops after a few months.
4. Travel Rules
Most airlines allow power banks up to 100 Wh in carry-on luggage without approval, 100–160 Wh with airline approval, and never in checked baggage. When a guide is about travel, we state the Wh rating of every product we mention so you can check it against your airline.
5. Sources We Use
- manufacturer specifications and certification marks
- real product listings and their technical sheets on major marketplaces
- recurring patterns in verified buyer reviews — not single opinions
- published charging standards (USB-IF Power Delivery specifications)
What This Method Does Not Do
We are a small editorial team, not a certified laboratory. When a number comes from our own calculation, we show the formula; when it comes from a manufacturer or buyer reports, we say so. If you spot an error or have measured something yourself, tell us through the Contact page — corrections are added to the article with a note.
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