The clearest indication that your laptop battery needs to be replaced is a significant decrease in its ability to hold a charge. If your battery used to last for eight hours, but now it only lasts for three or four, your battery may be dying. A battery on its very last legs will not even be able to power your laptop for more than a few minutes. Many computers have a built-in system that will alert you to a damaged or poorly functioning battery. If your battery has ceased to function properly, take your laptop to a repair specialist immediately.