Need to be real careful when hooking-up any sort of battery charger on a mk7.
Most (all?) mk7s have a battery monitor which sits on the negative terminal of the battery (see pic below), The purpose of the battery monitor (it's part of the power supply LIN bus) is (amongst other roles) to keep a history of the electrical current that is used/inputted) to/from the battery. It provides most of the basic data for the calculation of what VW calls the System Voltage. System voltage (not battery voltage) is what the control modules use when making decisions related to the vehicle's rail-volts.
Anyhow, it's important when charging a mk7 to INCLUDE the battery monitor in the charging circuit. This means that battery chargers should not be connected directly across the battery (i.e. positive-to-positive and negative-to-negative)
The correct way to charge a mk7 is to hook the positive lead of the charger to the battery positive and the negative lead to the special lug that is near the battery terminal (see picture below) - not to the negative battery terminal. If this isn't done the battery monitor is by-passed and the charging current is never recorded!
Don
