Electrical- something keeps killing my car battery.

You have a parasitic draw on battery

How to identify and locate a parasitic drain - YouTube

this is called a parasitic drain. It could be a trunk or glovebox light that isnt turning off.

Hello Jr, The fact that the battery goes dead even with a kill switch would lead me to think the new battery is defective.

I would take out any fuses that I dont need running that kills the battery.

use a volt meter see where you are loosing the power sounds like a big drain anything can do it so i would first check all my fuses and replace them it see it im getting a constant flow or big drain through them if you have an after market radio i would replace that and see if that helps i had the same problem with mack truck after market radio was pushing more then 16.8 volts crazy would kill the battery in just a few hours

you are looking in the wrong place. something is draining the battery while the ignition is off. replacing the battery and alternator is never going to fix this. you have to have someone troubleshoot the electrical system and figure out which doodad is killing the battery. usual
suspects are lights which aren't noticed as in the trunk and glove box, the anti-theft and door lock systems, remote start, clocks,etc.

One of those buggers is draining your system, you have to find it and kill it.
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Check for a drain by putting an inductive ammeter probe around the positive or negative wire on the battery.

If there is more than .2 Amps of draw when the car is not on, then you have too much of a drain caused by something in the car's electrical system.

Take the car to an auto electric shop to try to find the short or source of the drain.

check your alternator its what keeps battery charged if the alt is defective it will not charge battery draining it fast..

buy cheap tester check alt for output 14-16 volts, check for blown fuses

If you have a volt meter check to see if there is a drain on the battery when the car is off, you can then pull each fuse to see which circuit is causing the draining. Sounds easy, but I have also seen cases where somone left change (a penny) in the cigarette lighter causing a short cirucit.