1998 Ford Taurus batery dies

My 98’ Taurus will not hold a charge. I have replace the battery 3, The altinator was replaced 4 times, and the 175 amp mega fuse was replaced once.
I am at wits end cause I don’t have a clue what is causing the the battery to discharge over night in the winter and with in 3 days in the sommer. I have rewired the main fuse box under the hood cause the relay to the starter melted the box, I replaced cables to the battery, the altinator, the starter, and the ground to the battery, and the main fuse box under the hood.
I have tested the batery to see if it will hold a charge on its own. This test took 3 weeks before it drained. I know it is not the battery.
Anyone have an Idea of what is going on with this car, Did I miss something?

"I have tested the batery to see if it will hold a charge on its own. This test took 3 weeks before it drained. I know it is not the battery. "

I don’t know what you’re saying. You disconnected the battery to see how long it would hold a charge? What voltage did it start at? What voltage was it at after 3 weeks? A healthy & fully charged battery should be able to sit for 3 weeks & still have no trouble kicking over a car.

You need to look for parasitic drains while the car is turned off - especially after you “rewired the main fuse box.” The web is full of instructions for that. It just involves using a multimeter to measure current draw with the car & all of its stuff off, and then usually pulling fuses one by one to see what happens. Here’s one of about a thousand web guides: http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains

You also need to worry about the main power cables in the car. If you measure at the alternator with car idling, what is the voltage output? What is it if you measure at the battery?