Experts estimate that 5% of the electricity used n the United States goes to standby power. They say we could save almost $4 billion a year just by unplugging battery blocks when the device is charged. Most of us just unplug the device and leave the charger plugged into the wall when we really should unplug the cable from the wall.  While this advice is perfect for cell phones, it also applies to PDAs, toothbrushes, and portable tools. Many of these devices trickle a charge even after the device is fully charged.