The VL-DS4 four way discharger discharges four V-Lok batteries in sequence and provides a current state of discharge on its LED screen, providing users with the knowledge of the batteries current Ah rating. This product therefore is ideal for rental / production houses who want the guarantee that the batteries they are sending out are fit for use. Discharging begins once a battery is attached to a channel and the start button is pressed. Ideally attach the first battery to channel 1 then so on, as the unit will always discharge in sequence. A true reading is only provided if a fully charged battery is attached to the VL-DS4.