GoKawiilRita El Khoury / Android Authority
If you’ve ever felt slightly cheated by even the best power banks, you’re not alone. At first glance, a 10,000mAh battery pack looks like it should recharge your 5,000mAh flagship phone twice without breaking a sweat. Yet somehow, the numbers never seem to work out quite that neatly. A charge and a half, or thereabouts, ends up being much more realistic.
The good news is that your power bank isn’t lying to you. The bad news is that battery capacity is a little more complicated than the box’s marketing makes it seem. The milliamp-hour (mAh) figure you’re looking at doesn’t represent the amount of charge that will end up in your phone, and that’s where most of the confusion begins.
Would you buy a smartphone just for a 9,000mAh battery? 861 votes Absolutely, more is always better. 45 % Only if the software optimization backs it up. 41 % Not really, I care more about other specs. 13 %
The big misunderstanding about power banks
Edgar Cervantes / Android Authority
When shopping for a new power bank, we’re all eyeballing that headline mAh figure — it’s a metric we probably have a rough gauge for based on our daily experiences. If our 5,000mAh phones last most of the day, then an equivalent battery pack would surely be plenty for a day trip, while a 10,000mAh or 20,000mAh pack would surely do for a weekend’s camping trip.
However, mAh is a relative, not an absolute, measure of power. The listed value refers to the capacity of the internal lithium battery based on its “nominal” operating voltage. This is typically 3.7-3.85V for a Li-Ion battery pack, but this varies slightly depending on the exact battery chemistry. However, some manufacturers also report their mAh rating as equivalent to a 5V, 20V, or some other output, depending on the intended use case.
Sadly, a 5,000mAh battery pack can't fully-charge a 5,000mAh phone.
So the first real complication is that the pack’s reference voltage may differ from the device you’re trying to charge. Your phone might have a nominal operating voltage of 3.6V for lithium-ion to 3.9V for silicon-carbon batteries, but your laptop might be 11V to 16V, depending on the number of stacked cells and its age. Tablets, smartwatches, and other gadgets have their own specific internal voltage requirements.
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