It is not necessary to use the device connected to the electrical current. In fact, doing so could be harmful and shorten battery life. However, in the event that it is necessary to complete a program in progress and the battery is about to run out, the device can be connected to the electrical current. At the end of the program, it is important to ensure that you carry out a full charge of 8 to 9 hours. When the battery begins to fail, you can choose to use the device connected to the electrical current or replace the battery with a new one.