ELI5: Why do batteries degrade over time

Batteries degrade over time because their insides slowly change and wear out each time you use them.

Imagine a battery is like a cookie jar full of energy cookies. When you use your toy car (or phone, or remote), you're taking out cookies from the jar. Each cookie represents a bit of power.

• Chemical Changes: The "cookie dough" inside the battery, which stores the energy, starts to clump together and change its texture over time. It's like leaving your real cookie dough out too long - it gets hard and not as good. This means the battery can't store as many energy cookies as it used to.

• Impurities: Tiny bits of "dust" get mixed into the cookie dough. These impurities interfere with the battery's ability to properly hold and release energy. Think of it like adding sand to your cookie dough – the cookies won’t taste as good, and you can't make as many.

• Physical Wear: Imagine that every time you take out a cookie, you slightly scratch the inside of the jar. Over time, these scratches make the jar weaker and less efficient. Similarly, inside the battery, parts wear down little by little with each use, preventing it from working as well.

• Heat: Leaving the cookie jar in the sun makes the cookies melt and stick together, right? Heat does the same thing to batteries. If your battery gets too hot (from charging too long or being left in a hot car), it degrades faster.