A device includes an interface configured to couple a power source to the device. The interface includes a plurality of contacts including at least one first contact configured to couple a voltage bus of the power source to a voltage bus of the device, and at least one second contact configured to couple the voltage bus of the power source to a secondary bus of the device. The device further includes a detector configured to determine a contact resistance of the at least one first contact based on a first current associated with the voltage bus and a second current associated with the secondary bus.