“How long does it take for a Li-ion battery to degrade?”

(Answer requested by Jake Timchak)

Degrade by how much? Lithium-ion batteries are “consumables” that inevitably get used up, even just sitting on the shelf.

Li-ion batteries actually start degrading (very slowly) the moment they’re assembled at the factory. Each discharge/recharge cycle then accelerates the irreversible chemical changes in the battery, ever-so-slightly reducing the battery’s capacity.

How slightly? If you follow recommended 80/20 practice as much as possible — try to recharge when the battery’s no lower than around 20%, and stop charging no higher than around 80% — a Li-ion battery in daily smartphone or PC use can lose less than 10% of its capacity per year.

But hard use — full charge/discharge cycles, constant use of “fast” and wireless chargers, etc — increase wear significantly.

I don’t have the reference at hand right now, but I believe the rule of thumb that manufacturers use for warranty claims is that “normal wear” allows a battery to lose about 20% capacity a year.

Two years of 20% losses mean that the battery would only have 64% of its original capacity; three years in, it’d have just 51%.

So, it matters a lot how you treat your Li-ion batteries, especially if you keep your devices for more than a year or two.

All batteries will inevitably degrade, but you can control how quickly!

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