Any Ford techs in the house?

I've been helping a friend of the family with an increasingly frustrating problem on an '07 Ford Five Hundred.

They bought the car from an auction back I June. It looks clean and well kept and has a little over 100k miles.

The battery kept dieing, and it would often have a charge system warning.

I found the alternator was only putting out 13 volts, and would drop down to 12.4v with all the accessories running. Seemed like a no brainer, replace the alternator.

So I did, and charged the battery overnight too.

A couple weeks later the car had a dead battery again. I told them to replace it, because it was pretty old, and they did. About two months ago the car started having an intermittent dead battery, and even shut down once or twice. The only fault code recorded was P0563, system voltge high. When I came and tested it it was fine other than a discharged battery.

So, I figured even NAPA reman alternators can fail, so I exchanged it for another one, and recharged the battery. This time the problem came back in only a couple of days. The charge system warning was back, the only code was P0563, the car nearly stalled while being driven.

I came and checked it out today. The battery had just barely enough juice to start the car, but once it started the output was good at 14.4v. P0563 was the only logged fault.

These are known for the harness rubbing on the AC lines and causing problems, I checked that and found no problem. I also checked where the harness runs under the battery tray, no problem there either.

What could I be missing? The internet says that this is not an unknown problem, and that only a brand new OEM alternator will fix it, because the alt is controlled by the PCM, and the circuit in the alternator that communicates with the PCM is the problem. I Don't quite believe that, how can I tell if it's not the PCM that is at fault? How would a failure in that control circuit cause the battery to die?

I'd start by checking for draws on the system with the key off. Fords can take a while (like 45 minutes) for all of the modules to enter "sleep" mode so the best way to check it is with one of the fancy clamp style meters.

You can do it with a regular meter, but you'll have to hook up a wire that can carry a heavy load between the battery and the battery cable in addition to the meter. This way most of the load goes through the the jumper wire and doesn't fry your meter. Then after all of the modules are asleep (make it an hour to be safe) you can unhook the load carrying wire and see what the draw on the battery is in mA. Ford spec is under 50 mA, usual draw on a healthy system is under half of that.

checked for loose battery cable at the terminals? I had a similar problem with the F150 I just bought. the previous owner had been through countless batteries over the last YEAR and replaced the alternator as well. They "figured it out" to be a glovebox light that was staying on and installed a piece of wood to keep it off with the glovebox open. Being that there was no glove box light scandal between Ford and battery manufacturers I thought they were wrong so I took the wood out. Two day later, dead battery. So I bought a new battery. Three days later, dead battery. It tested good but no start. Then I remembered to start with the cheapest part first, so battery cables. I thought to yank on them just to make sure I had good connection and the negative was solid but the positive just slid right out. Well there we go. After reattaching the positive cable, no more issues. Starts every time.

In reply to gunner:

Battery cables are OK. I suspected that there was a problem with the positive cable, because it had corrosion, but after I cleaned it up, it wasn't bad at all.

Engine and chassis grounds are good.

I'd verify a lack of draws per psychic_mechanic. I open the doors and reset the latches with a screwdriver so I can get access to the in car fusebox without waking everything up again.

Could be alternator. Could be something else.