What is the voltage output of an Apple 85W MagSafe 2 model A1424 without a load?
I believe these are smart chargers, and initially only supply about 3 volts in order to power a power management chip inside the device to be charged.  Once powered by the 3 volts, the power management chip inside the device then communicates with the charger verifying that the device is compatible to be charged, and if that fact is verified, only then will the charger output full charge voltage.

Additional info provided by @MarcWilson.