Why Do Batteries Die?
No battery lasts forever! Even rechargable batteries that come with devices like laptops, power tools, cameras, and camcorders do not last as long as they do the day you get them. Here's a little bit of information about why this happens.
Think about a laptop battery for a second. Even though it might not seem like it, that battery never charges back up to 100% even though the gauge says it does. Although imperceptible at first, the chemicals that make up a battery cannot fully refresh no matter how long you charge for.
Believe it or not, that laptop even loses power when it's turned off! Again, the loss is very minimal over short periods of time, but if you've ever left a laptop turned off for a long time then tried to power it up on the battery power, it probably didn't even turn on. If it did, that laptop battery probably didn't last very long.
What happens inside a battery is that the energy produced to run the device occurs as the result of a chemical reaction. This reaction is different depending on the type of battery you are using. For example, a lithium-ion battery generates power when lithium ions move from one electrode (negative) to the other (positive). When charging, those ions are sent back to the positive electrode and the process starts all over again.
However, over time deposits can form inside the battery that create internal resistance and reduce the effectiveness of the battery. These deposits are what eventually result in the battery refusing to take a full charge or not charging at all.
So if you have had a battery for a long time and your laptop won't charge, it's likely not a problem with the laptop. It's probably that the battery has just lost it's luster.