I've had the same issue with my Taurus where it seems something is drawing some extra battery power. I narrowed my problem down to crappy factory battery cables. The cable rusted and fractured. So it wasn't making a good connection on the terminal.

Keep an eye on your coolant lines on your Taurus. Especially the tube assembly on the back firewall attached to the heater core. They have been known to "burst". Happened to my wife (while she was doing 70mph on the highway).

There are also other known issues such as dome lights now going off when you shut the door, and the door ajar light staying on. Those are known and common problems with the model you have. If the car has over 60k miles on it I would suggest replacing the camshaft position sensor. That one "always" goes. The replace job isn't too bad either, and can be done at home.
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