You should plug the input jack from the available charger to the 18V battery or simply place the battery in it. Adjust the valid charge rate (if possible) and make sure that its exponent isn’t higher, as you can damage the battery. 2. Connect the charger to the electric power source and turn the charger on. 3. Leave the unit for a few hours and keep a check on the light color changes. 4. Unplug the charger and remove the jack or the battery from the charger.