Battery is the most important component of a phone. In fact, a phone is useless without a stable battery, because the activeness of the phone is directly proportional to the battery. Although the battery technology has progressed a lot and the phones using them have become smarter too, but there comes a point when a phone battery gradually lost its charging capacity over the time. Lithium based batteries, which are mostly used in phones these days, usually starting to lose their charge capacity in a time span of 1 to 2 years. You can watch out for certain signs, if these appear with your phone, then there is high chance that your battery is faulty and you should replace it with a good one.