This is a Profoto Universal Power Adapter for the Pro 7B power pack. This unique item adapts the Profoto 7B battery powered power pack, via the car charging socket, to any AC power source.
Technically, this is a trickle charger that allows tapping in of the AC power being used to recharge the battery.
As a charger, it provides a full charge to the battery in only 2.5 hours, less than half the time of the standard charger. It senses when to stop charging, so it can be plugged in all the time. It attaches to the side of the 7B with magnets.