A short guide to reading a battery specification sheet without being misled by the single largest number printed on the front of the box
Capacity is the number manufacturers put in the headline. It is rarely the number that decides how long the device lasts in your hand.
A battery specification is a small table pretending to be a single number. The figure on the box is almost always capacity in milliamp-hours, and on its own it tells you very little.
Capacity is not energy
Milliamp-hours measure charge, not energy. Energy is charge multiplied by voltage, and two cells with identical mAh ratings can hold noticeably different amounts of energy if they run at different voltages. Watt-hours — the figure airlines care about — is the honest comparison, and it is usually printed in smaller type on the back.
The number that actually varies
Between two devices of similar capacity, the difference you feel comes almost entirely from what the device does with the energy: display brightness and refresh rate, radio behaviour when signal is poor, and how aggressively the system idles. A larger cell attached to a hungrier screen is a wash.
What to look for instead
Watt-hours for a real comparison, charging wattage for how quickly it recovers, and — the one most specification sheets omit — the rated cycle count before the cell drops to eighty per cent of its original capacity. That last figure is the closest thing to a durability rating a battery has.
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- How this was made
- Original reporting and writing by Webitlio.
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