Laptop batteries don't last forever, unfortunately. Over time and with usage, batteries wear out and need to be replaced. This can happen anywhere between one and four years, depending on how often you use your laptop and what you use it for. Fortunately, replacement batteries for Toshiba laptops are readily available and are not hard to replace.
Purchase a replacement battery for your Toshiba laptop model. To be sure you have the right battery, go to Toshiba's laptop battery finder website, or another laptop battery site with a good search feature.
Turn off and unplug the laptop.
Turn your laptop upside-down, so you are looking at the underside of the laptop. Locate the battery. The size and location will vary depending on the model of the laptop, but it is generally a large, square or rectangular area with one or two latches that lock it in.
Unlock the switches and slide the battery out.
Place the new battery in the same way you pulled the old one out, and secure the latches.
Do not throw away your old battery. It can be hazardous to the environment. Find a battery recycling program in your area.