DEWALT DCB204BT-2 20V MAX 4Ah Compact Battery with Blue Tooth (2 Pack) Connect. Control. Alert Allows you to connect your battery to your smartphone via blue tooth technology On screen diagnostics of battery status Ability to turn on or off connected batteries at once Lightweight design and 35 minute charge time *Maximum initial battery voltage (measured without a workload) is 20 volts. Nominal voltage is 18