Alternator/battery/cable issue

[Infich]

Hello All
First, forgive me my English, I'm Russian.
This is my 1st post here.
My details: 2013 Lim+, 294 hp

I'm very tired with goddamn issue - Check charging system (and battery icon).
Diler told me that this is because of alternator itself. A new alternator costs too much and also I don't believe diler . Moreover, I was told from one electric guy that ford alternators are pretty lasting.
So I found some used alternator with poor mileage and replaced it. Also I replaced the battery by new one.
But I was happy 3 weeks only. Now that message appears again (check charging system).
So my next thought is a cable. Cable part number is DB5Z-14300-B (by my VIN).
So my qestions are:
1) From where does this cable go to? From alternator itself?
2) Is there (within the cable) a wire from alternator to PCM (let me call it the 'car brain'). Because last year I had the same issue and it was fixed by repairing that wire. It was corroded or smth like this. So maybe it just happened again.
And offf topic question. Why the cable called BATTERY TO BATTERY? It should have been called ALTERNATOR TO BATTERY cable, isn't it?
3) If it's not a cable, then what is that???

Thanks in advance.
Have a nice day to everyone

 

[Rainlord]

How often do you drive it? I get that warning quite a lot, and in my case, I don't drive my car that often (once/twice a week, usually weekends), so for me it somewhat makes sense as something will be drawing power from it even when it just sits there. After a long drive it takes a long time before I see it again. I have yet to do a check for a ghost battery drain, but I should.

#1. Here's the drawing of where the cable goes.

#2. I can't answer that one
#3. Do the ghost drain check, it's very likely something in your car is eating up your battery.

 

[Infich]

How often do you drive it?
#1. Here's the drawing of where the cable goes.
#2. I can't answer that one
#3. Do the ghost drain check, it's very likely something in your car is eating up your battery.

I drive it every day.
Yeah, I saw that drawing before, but it doesn't fit my question. Wire just goes somewhere into a car on this drawing.
Thanks for ghost drain check. I'll do. Actually, I'm pretty sure there's no extra battery drain, but anyway.
Thank you.