Jeff's old Android phone is dying really quickly. Leo says it's likely because it's nearing the end of it's rechargeable life. Phone batteries have a limited number of charge cycles, at about 500. After which, it will die pretty quickly and won't take a charge anymore. That's why it's best to leave the phone plugged in all the time unless he's out. It will preserve that limited amount of charge cycles, and it's perfectly safe to do so. If it's not holding a charge, it's worn out and the battery needs to be replaced.