Battery Charging Scheme

So, Ford has been using a so called "smart charge" system for quite a while now. This system can be a bit confusing for auto electricians (but a few seem to be catching on). The main thing that will be noticed is that, with the engine running, the battery may not have the "usual" (like it has been up until smart charge systems came in) 14.4V Instead, much of the time, a float/maintenance charge is applied at approx. 13.7V

With Fords, the PCM decides what voltage the alternator should put out on the B+ terminal and varies the voltage according to conditions. This article provides a useful insight into the type of scheme but uses GM's system as an example.

What I would dearly love to have is a similar description of Ford's scheme. By this I mean that there is a PCM parameter called GENVDSD (generator desired voltage) which is the target voltage the PCM requires from the battery/alternator. This ought to be reflected by the battery terminal voltage (you'd think) but I have a contradiction to this in our C-MAX.

If it was like the GM system, GENVDSD would rise to 14~15V shortly after starting (to replenish the lost charge during cranking) then fall back to 13.7V to save wasting power cooking the battery. The article above shows two graphs that differ according to temperature. Various sources on the net describe similar allowances made for battery temperature in Fords, but nothing specific.

In our C-MAX the 3yr old battery was replaced as it wouldn't hold charge. Suspecting the charging system I've been trying to diagnose the problem with very little success. I have all the right tools ('scope, OBDII scanner) but lack the information about the expected charge sequence that the PCM applies. In my tests it ALWAYS asks for 13.6 and never anything else. I am deeply suspicious about this but find it hard knowing how to approach the "trade" with such a technical concern. I've already been "sent away" by the garage we bought the car from (they say they've double checked it and it's all OK, but when I start talking technical, we just go round in loops until I run out of breath).

Does anyone have a snippet of info that might reveal the correct sequence for GENVDSD? I can monitor batter voltage which matches GENVDSD with no electrical load, and GFS (generator field strength) which does go up and down according to load, but at the same time the battery voltage falls (e.g from 13.7 to 11.8) while GENVDSD stays put at 13.7

Here is a screenshot from the Torque app that shows the battery down at 12.1V with the engine running and heated screens/AC/Lights all on. Unfortunately GENFDC (the field command to the alternator) is highly intermittent and reads incorrectly but the other readings are good.