Why your phone battery dies so fast (and what actually helps)

Lithium-ion cells degrade predictably. Understanding how turns battery care from superstition into three simple habits.

Heat is the main villain

A battery held at 40°C loses capacity several times faster than one at room temperature. Fast charging in a hot car is worse for long-term health than almost anything else you can do.

Charge cycles, not charge count

One cycle is a full 100% of capacity used, however you get there. Topping up from 60 to 80 five times is one cycle, not five. Plugging in whenever you can is fine.

The 20–80 rule is real but overstated

Keeping a cell near full charge for long periods does accelerate ageing. If your phone supports optimised charging, turn it on and stop thinking about it.

What actually helps

Take the case off during fast charging, avoid leaving the phone in direct sun, and replace the battery at around 80% health rather than replacing the phone.