Disable proximity on the fob as a test. This will prevent the car sensing the fob and requires holding the fob against the start button to start the car, rather than just have it somewhere in the cabin.

This will prove or disprove the "constant communication draining battery" argument.

 

I learned to disable the key fob when camping after ending up with a dead battery.

 

This is a known and well documented problem (as advised by your Subaru service centre)

Solutions are to “disable the fob” by following the instructions in the owners manual.

Keep fob wrapped in aluminium foil or a special bag to prevent it communicating with the vehicle.

I think you may also be able to remove the battery from the fob. If the battery is removed you will need to place the fob up against the start button (placing the fob against the start button will turn the start button light green which then allows the vehicle to be started).

Hope this helps.

Seagrass

 

I have been involved with this type of discussion for years and with a few different manufactures. My keys hardly ever leave my vehicles (3 vehicles) and I don t believe it does anything negative to the battery. Some service advisor of coarse is going to blame you and the key. What I ve researched is that when the key and the car, even when together, sit dormant for a certain period the system goes to sleep.
I have done this since key fobs first became a thing so this is what has been true for me. I don t think I even remember a dead battery EVER .
Maybe your parking attendant s are sitting in cars with radio s on?
As for the dealer, did they tell you they have had lots of problems with 2020 batteries? (That s a fact).

 

I have been involved with this type of discussion for years and with a few different manufactures. My keys hardly ever leave my vehicles (3 vehicles) and I don t believe it does anything negative to the battery. Some service advisor of coarse is going to blame you and the key. What I ve researched is that when the key and the car, even when together, sit dormant for a certain period the system goes to sleep.
I have done this since key fobs first became a thing so this is what has been true for me. I don t think I even remember a dead battery EVER .
Maybe your parking attendant s are sitting in cars with radio s on?
As for the dealer, did they tell you they have had lots of problems with 2020 batteries? (That s a fact).

Which would lead into a question for @grantnyc - how many times might they be starting your car to move it a short distance to access another vehicle? Are the lights on during that cycle? It's possible they're just running the battery down into the 'no start zone' just in the way the vehicle is managed within the garage.

Which would lead into a question for @grantnyc - how many times might they be starting your car to move it a short distance to access another vehicle? Are the lights on during that cycle? It's possible they're just running the battery down into the 'no start zone' just in the way the vehicle is managed within the garage.

Interesting point hallux. We're mostly using public transit during the week and we typically drive it once every 2-3 weeks (maybe averaging 8-10 hours of runtime a month). I think the attendants might only have to move it once or twice in between us using it. Guessing though. For context, we've had two other vehicles (with fobs) in the same garage, and zero dead batteries. Wondering if the 2020 OB batteries just weren't up to snuff for this use case.

 

I have stored my fob in the cup holder of my 2020 ( in my garage) for days on end. ( Regularly up to 3 days straight) It has not been a problem in the two years I've owned the car. You have something else going on there. That said, Our power management system sucks. I can tell you it only takes 1/2 hour or so of running the car in ACC mode to kill the battery though.

BTW, If you want to test this yourself, you can put the fob to sleep or have them store your fob in a metal box /faraday bag to be sure.

 

@RocketMan20 are your driving habits or are you doing something else to make sure your battery is well charged before leaving it for days with the fob in the cup holder?

I'm wondering if some people have marginal battery charge when they leave the fob in it and while it's not a huge parasitic draw, it's just enough to take a battery that's marginal into the no-start zone?

 

I'm wondering if some people have marginal battery charge when they leave the fob in it and while it's not a huge parasitic draw, it's just enough to take a battery that's marginal into the no-start zone?

Which would lead into a question for @grantnyc - how many times might they be starting your car to move it a short distance to access another vehicle? Are the lights on during that cycle? It's possible they're just running the battery down into the 'no start zone' just in the way the vehicle is managed within the garage.

 

...also as cerbomark alluded, this could also be a function of the 2020 OB's not going into to sleep mode in a timely manner. If so, it would seemingly be fixable with a software update. I understand the downside could be that remote app functions wouldn't be unavailable after sleep mode kicks in. But I'd rather have a protected battery vs continued remote abilities.

 

Makes sense. Thanks for explaining how it works. To answer your Q, the lights would be on for those instances (since it’s a fairly dark environment and they’re left on “auto”). I could see how numerous starts without much runtime could drain the battery. From what I understand, cars started, but run less than 15-20 mins likely results in battery charge lost, not gained. That said. I don’t think they’re starting it so often that it could be fully draining, but I’ll see if I can track how often it’s started on the MySubaru app.

 

The fob was left in our car for about 5 weeks while it was in the body shop with no ill effects, and that was the original OEM 620CCA battery.

That being said, our replacement EFB from AutoZone has performed much better; recently I’ve seen start-stop cycles lasting a full two minutes in stop and go traffic for 20 minutes that included waiting for a train.

It’s not that our original battery was bad per se, but the replacement battery has been noticeably better with much more stable voltages. Most of the time during the day it doesn’t charge at all during driving, and of course at night there’s a constant charge since the lights are on.

Bottom line, at least from my experience, is just drive the car normally and if your battery is weak get a new one. SOA reimbursed us the $200 for the replacement battery at 18 months.

 

Place the FOB in a metal case which is a Faraday Cage. It can easily fit in the small storage area under the dash USB ports.

 

All conditions contributing to the described drained battery are likely understated or unknown. Eliminating the FOB as the source or contributor to the stated problem may not be worth the effort unless there is a reoccurrence of this problem with the replacement battery. If the problem goes away then the cause was either the FOB or battery or a combination of the two

Please post information describing the replacement battery that is now in your car. Is it a dealer installed LN2 battery? If so, is it 620CCA or 640CCA?...

If it were my vehicle and the problem reoccurs, or maybe not, I would initiate the following:

1. Insure the FOB is not communicating. Multiple choices are available including the removal of the FOB battery and going to tap to be able to start the vehicle. The second FOB can be fully operational but should be kept in a Faraday container.
2. When your are taking the vehicle out for a drive, turn on the lights, parking or headlight, to keep the alternator running at full charge. Seems that the car's brain allows the battery charge to drop from full charge to save gasoline. Look for SilverOnyx posting for more info. At the same time, reset your stay-on times for exterior/interior lights to be as short a time as possible.
3. Switch-off all lights when leaving it in the garage. Make sure switches are not set to auto for all exterior and interior lights.
4. Ask the parking attendants to always park your vehicle in a location that it will not likely need to be moved. Starting the car resets dormant timers to begin running again and interior and exterior lights will be activated and remain on upon exit. A door adjar may not be noticed because attendants are use to seeing these light on after egress.