A power tool battery, battery charger, and a method of operating the same. The battery and the charger can be lockingly engageable with each other. The battery can be electrically coupled to a charging circuit of the charger for charging the battery. One of the battery and the charger can include a protrusion and the other of the battery and charger can include a recess for receiving the protrusion. The method can include inserting the battery into the charger along an insertion axis and charging the battery. The method can further include rotating the battery about the insertion axis to secure the battery with the charger while continuing to charge the battery.