When to replace a laptop battery

We all know the frustration: your laptop says 20%, you start a video call, and the laptop instantly dies. You plug it in, and it boots up saying 18%. This isn't a software glitch; this is the chemistry of a dying lithium-ion battery.

What is a Battery Cycle? A cycle is not just plugging and unplugging your laptop. A full charge cycle occurs when you have used 100% of your battery's capacity. If you use 50% today, charge it full, and use 50% tomorrow—that equals ONE cycle. Most laptop batteries are designed to retain 80% of their original capacity for roughly 500 charge cycles.

Internal Resistance and Voltage Drops: As a lithium-ion battery ages, the chemical structure degrades, and its 'Internal Resistance' increases. Think of resistance like plaque in an artery. When your laptop suddenly demands a large spike of power (like opening the camera or turning up brightness), the degraded battery cannot push the electricity through the resistance fast enough.

The voltage drops below the critical threshold required to run the CPU, and the laptop forcefully shuts down to protect itself. This is why a degraded battery causes unexpected shutdowns.

When is it time to replace? Software 'Battery Health' percentages are estimates. The true indicators are: 1) The battery swelling (pushing the screen up), 2) Unexpected shutdowns under 20%, and 3) The laptop dropping from 100% to 80% in just minutes.

Replacing a battery is a simple, affordable job that brings an older laptop back to full use, for far less than a new laptop.