To increase the life of a Roomba's battery, you need to take care of a few things. For instance, make sure you only use iRobot batteries for your Roomba cleaner. Also, you can also fully exhaust batteries in order to fully charge them again. In addition to that, keep the Roomba plugged in when it's not in use. Moreover, keep the brushes clean from debris and other dirt particles. By following all these steps you can increase your Roomba’s battery life.