Alternator

No, no alternator, just a 100 Amp DC to DC converter.

If there was an alternator, the 12 battery would only charge when the engine was running, so it would need to be much larger or the engine would start when you did not need it to go anywhere.

The 12 volt system is powered by a DC to DC converter attached to the big battery. If the big battery runs down, then the engine does start to recharge it, but that is rare.

This video is about the Gen 2, but I suspect the only differences are in packaging, not concepts. The bit about the converter starts just after 15 minutes in an lasts just past 18 minutes in. It also covers the air conditioning electronics as they are on the same circuit board in Gen 2. (The entire video is informative, but those 3 minutes are relevant to this discussion)

Some results of this system: a dead battery charges just as well anytime it is in Ready, no need for high RPM; you want to be in Ready anytime you are using a lot of 12 volt power; there is no advantage to adding ground straps to the engine, the engine is not very involved in 12 volt power, just spark plugs.

 

This video has Gen1, Gen2, Gen3, Gen4, Focus, and Volt inverters. Again no differences in concepts.