The 191U48-0 Power Source Kit consists of 4 x BL4050F 40V Max XGT Li-ion 5.0 Ah batteries & a DC40RB/2 240V twin port fast charger, supplied in a Makpac case. The MKP 5.0 Ah Power Source Kit is specially designed for use with 40V Max & 18V LXT products being used in continuous operation. The BL4050F is a 40V Max Li-ion XGT 5.0 Ah Battery, a new type of cell with increased water & drop impact resistance. Communication between the battery & charger, allows to read more detailed information on the battery usage history. The BL4050F communicates digitally between the battery & the tool & battery & the charger & is equipped with 4 LED battery fuel gauge with a check button & cooling system for maximum battery life. The average charging time for a BL4050F is Approx. 50 minutes. The DC40RB is a 240V Twin Port Fast Charger, designed for charging battery ranges from 14.4V LXT to 40V Max XGT; ADP10 Interchangeable Adapter Set is required (sold separately) to charge 14.4V & 18V LXT batteries. The DC40RB is not compatible with G-Series range of batteries. The DC40RB is able to charge two Makita 40V Max Li-ion XGT batteries at the same time as fast as a DC40RA charger charges one battery. The DC40RB performs consecutive fast charges of batteries for increased convenience & features optimum charging control using feedback of real-time battery data. DC40RB is equipped with large charging status indicator light, selectable melody sound for full charge notification, two cooling fans; one for the battery & the other for the charging circuit & electronic current limiter for overload protection. The DC40RB is capable of fully charging a BL4050F 40V Max 5.0 Ah battery in Approx. 50 minutes, BL4040 40V Max 4.0 Ah battery in Approx. 45 minutes & BL4025 40V Max 2.5 Ah battery in Approx. 28 minutes.