grand marquis electrical problem

[troubled2004]

I have a 2004 grand marquis. One day several months ago, the car repeatedly died both when driving down the road and when stopped. When driving, the car would, at times, restart itself. When stopped, the car easily restarted but might not continue to run. Bunch of engine lights would come on.

Had the car checked and no engine fault codes were found. It was suggested I had a bad tank of gas. The car started to behave normally.

Yesterday the car started to act up again as before. The car actually lost all power where even the clock stopped. I also noticed the car must have lost all power sometime while it was parked because the clock was off about 8 hours. When the problem first happened, all power also had to off when the car was parked as the clock was wrong then also.
Any ideas as to what is going on. Battery terminals were cleaned as well as ground terminal to engine and hot terminal to power distribution box between first and second occurances.
Any chance some internal issue within the battery is the cause?