Q: i have a ford expedition 98 and it stopped working out of the blue after driving for 20 min and parked we replaced the starter and

we drove the car to a store it started perfectly when we came out the store and try to start it it wont start just click the tow guy said its probally our starter so we replaced the starter and relay hoping that works still nothing and the car drained the battery in matter of min. i also smelled like wierd plastic smell and so we took it too two mechanics on starter guy and even the ford people they both said we need to get the keys reprogrammed so we did and since the battery keeps dying we have no way of knowing whats going on the alternator has been replaced 3 months ago along with radiator please help im out of clues
My car has an automatic transmission.