[Bigtoe32067]

A drain wouldn’t kill the battery only discharge it. It should be able to be recharged. Some chargers won’t initiate charge if the battery is completely dead.

I have similar problem in a 911 that will kill the battery Ina day or two and I have to use my old charger to put a little charge in it and then I can hook my new computerized charger to it and it will finish the job.
If I try to use the newer charger it says battery bad and won’t even try to charge. It just says that the battery is bad and shuts itself off.

It sounds like you have a pretty big drain if it kills it overnight. An acceptable drain on a battery is 50-100 milliamperes which is .05 - .1 amp. Anything higher than that means there’s a problem.
You have to let the car sit for about an hour with everything shut off, key out, and doors closed so everything will have enough time to shut down. If you do it too soon like 5 or 10 minutes then you’ll still see some accessory drains that will be mistaken for unwanted draws, these will shut themselves off after time.

I would suggest a battery cutoff switch so you can disconnect the battery electrically from everything once you’re finishEd driving while you’re trying to determine the cause. That a way you won’t keep going through batteries while trying to find the problem because it’ll recharge while you’re driving and stay charged once you disconnect it.

Harborman is correct.
Hook your multimeter up between the negative terminal on the battery and the ground or positive terminal and positive cable to determine the amount of the draw and then start pulling fuses to determine which circuit the drain is in. It’s just a process of elimination from there.

Good luck