Can a car battery be depleted if everything is turned off?

The battery of my 2017 Impreza has been depleted twice in the past couple of months. (December 2023 and yesterday.)

As far as I know, everything was turned off in the car when not being driven. However, the dealer told me that the car has 21 computers in it (probably meaning systems controlled by electronics). Also, the car has Bluetooth. Is it possible that the electronics is activated by my home electronics (such as my CPAP machine) when the car is turned off?


Just a couple of suggestions.

1st- Might want to get your battery checked. Batteries don’t like to be completely drained.

2nd- Check if you can shut down the electronics in the car after use instead of leaving them shut down by them self. (can take 10-15 minutes in some cars).
I lock my door and that shuts down the electronics in my car.



If it’s the original battery then it’s probably toast. You get 5-7 years out of a battery, then it’s time to replace. (They are recycled.)

There could be phantom drain, it happens, but if it’s near the end of its life then even just the daily loss due to cold weather or just sitting could be enough to drop it below the threshold of usability.


Yes, Goofy is on point; and most Subaru sites (along with most car battery sites in general) indicate that the battery life is “3-5 years, but can last longer.”


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I had a friend who dealt with this problem by disconnecting the battery when he parked in the airport for an extended trip. Not sure how todays computers would react. Would they all reset? Or wipe their programming?

It worked in the good old days.

If original battery, probably past its lifetime. Every time I’ve had a “5 year battery”, I’ve been lucky to get 4. And nothing is ever totally off. Many years ago I kept an old sports car for fun and drove mainly on weekends. Only thing it had that was on all the time was a clock. That was enough to run the battery down if I didn’t take it out for a regular spin. No telling with all the computer chips, bluetooth, wifi connections today.