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Keyfob killing battery?

29052 Views 27 Replies 14 Participants Last post by  oblo
Hello,

I know there are battery threads out there, however I have not been able to find any definitive answers or solutions.

I have a 2016 Outback 3.6R that just went out of warranty, so far over it's life the battery has died on me 5 times. The original battery seemed under powered and based on the threads and recommendations on here I replaced it with a Optima Yellow Top. Since replacing the battery, the new one has died 3 times. One of those times I know there was a light left on, the other two were for no apparent reason. The most recent was last night...I accidentally left my key fob in the car and thought to myself...I really hope it's not dead because I left the key in it...sure enough it was dead this morning.

I ordered a battery jump start pack because I can't trust this car anymore. I am wondering if anyone has gotten any more info or details on this issue? The two times my battery died and I can't figure out why, it seems like the key fob was withing close proximity to the car. I think that is what is causing it but I'm not sure, based on things I have read it should take weeks for the key fob talking to the battery to drain it completely.

I had the battery tested at autozone because it is under warranty, it tested good. I'm thinking about having the alternator tested to be sure that is not the cause, as well as start figuring out how to test current draws via the fuse box as some people have mentioned...if anyone has any more details on how to do this I would appreciate it.

Thanks for any help/info you all can provide...we love the car except the battery issues we have been having. To make matters worse we are now at 37K miles, so no longer under warranty.

-Bryan
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My understanding is that if the key fob is near the car it will "talk to it" causing unwanted current loss. I sleep in my car when camping and place the fob in a mint tin which has a flip top lid. Never had an issue.
I think I have read the FOB should be 20 feet away. Now throw some home walls in there and the distance may vary.

Throw a charger on it periodically is about all I can suggest really otherwise.
I wouldnt want to buy a car that has proximity carp.
I wouldnt want to buy a car that has proximity carp.
Valid point, in the future I will think hard about it...too late at this point.

Additionally, I feel like we are to the point with technology that manufacturers should be able to create a proximity key that doesn't kill your battery if left nearby...I feel it is a useful feature.
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This doesn't sound at all normal to me - did you have the parasitic draw checked?
How often do you drive it? Lots of short trips? Apparently, in the name of fuel efficiency, the charging system doesn't maintain the battery at full charge, so regular trips of significant length are kind of important. Leave it on a battery tender if all else fails.
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The fob will definitely drain the battery if stored close by. The fob and car battery will be constantly communicating. Stop buying new batteries before you spend time addressing the dark current drain. Read this thread:

http://www.subaruoutback.org/forums...tery-methods-battling-dark-current-drain.html

Quick start guide for you...Get in the habit of disabling your fob every single time you exit or stop the car. It takes two seconds. The linked thread and the manual discuss how to disable the fob without using foil or other faraday cage. Even if you use foil, you should use the procedure in the manual just to be vigilant.

A more extreme procedure is disable the car’s sensors. That is also quick and is discussed in the manual and the thread I linked above. You should also learn this more extreme procedure because you have an extreme problem.

Generally, we now live in a time when you cannot own a modern car in peace without reading the manual. Those days are over. There are so many critical things in the manual that you will NEVER learn on your own. You should read the manual, cover to cover, as if you are reading a novel.
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I read the comment about the constant drain if the fobs are kept within 20 feet or so of the car.....back when my OEM 295 CCA battery crapped out in its first year of use.....

Dealer replaced the battery with the larger 495CCA battery from the 3.5 OB and I preemptively started placing our fobs in an RF shielded cubby hole storage in our kitchen right where we always store our fobs.......and never had another problem...so...coincidence? Who knows? I doubt that Subaru is the only company whose fobs communicate 24/7 with the car if in range..........does the drain even amount to anything measurable? Doubt it but who knows..........

If that's the worst compliant or issue that I run into, I'm a happy lad for sure......

Steve
Personally, I think disabling the fob every time you exit the vehicle is totally unnecessary (it also entirely defeats the purpose, i.e., convenience, of a proximity key) - there is no reason to do this unless you have the battery load measurements to show otherwise. Since the idea keeps getting thrown out there, I'll try to take some measurements of dark current with and without the fob system active.
Personally, I think disabling the fob every time you exit the vehicle is totally unnecessary (it also entirely defeats the purpose, i.e., convenience, of a proximity key) - there is no reason to do this unless you have the battery load measurements to show otherwise. Since the idea keeps getting thrown out there, I'll try to take some measurements of dark current with and without the fob system active.
Disabling the fob is NOT inconvenient at all relative to the problem in the original post. The original poster currently does not have the luxury of being a happy-go-lucky, non-thinking, Outback owner. Context matters here.

Anyway, have you even tried to go through the procedure of disabling the fob? It literally takes two seconds max. When you re-enter the car, you just have to press the unlock button, and everything is back to normal. That is a business-class, first-world problem if you think that is too inconvenient. (“Too inconvenient, I would rather risk a car battery drain than reach in my pocket and press the fob button.”)
Disabling the fob is NOT inconvenient at all relative to the problem in the original post. The original poster currently does not have the luxury of being a happy-go-lucky, non-thinking, Outback owner. Context matters here...
Sure, but you're making assumptions with incomplete information. We haven't established if the battery drain problem has been fully diagnosed (which isn't exactly a simple process, see here: https://subaru.oemdtc.com/TSB/07-85-14.pdf). More info is also needed from the OP regarding driving habits. There's nothing wrong with your suggestion to disable the fob, except for the fact that you have no idea what effect that has on the parasitic drain (which I've now volunteered to investigate). Of course, the OP is free to try that and see if it helps, but I personally think it's not worth it unless we know it has a significant effect. I think I've been clear that this is entirely my opinion, so no need to be defensive.
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How can you tell if its too close? I've tried leaving my keys inside my place on they key hook, then going down to my car and seeing if the doors unlock or if there's anything that looks like the key is too close. Luckily it doesn't unlock, but could the key still be "communicating" with the car causing a drain?
Sure, but you're making assumptions with incomplete information. We haven't established if the battery drain problem has been fully diagnosed. More info is also needed from the OP regarding driving habits. There's nothing wrong with your suggestion to disable the fob, except for the fact that you have no idea what effect that has on the parasitic drain (which I've now volunteered to investigate). Of course, the OP is free to try that and see if it helps, but I personally think it's not worth it unless we know it has a significant effect. I think I've been clear that this is entirely my opinion, so no need to be defensive.
The manual almost blatantly says there is a dark current drain issue with the fob. Also, again, disabling the fob takes about a million times less work than dealing with a dead battery. Saying it is not worth a try makes absolutely no logic sense.
This doesn't sound at all normal to me - did you have the parasitic draw checked?
How often do you drive it? Lots of short trips? Apparently, in the name of fuel efficiency, the charging system doesn't maintain the battery at full charge, so regular trips of significant length are kind of important. Leave it on a battery tender if all else fails.
I have not had the parasitic draw checked, i live 1.5 hours away from a dealer so it's not easy to get work done. I'll look into this test and see if i can do it myself or have someone nearby do it.

I drive it 3-4 times a week, with trips varying from 5-20 minutes mostly. I also use it anytime we go on a longer trip so 1 hr+ every other week or so. I have driven my other car <5 min to work every day for a year on the original battery with no issues...I know it's irrelevant but I think there is a bigger issue than the length of my trips.

I will consider a battery tender, keep doing some testing, and it sounds like most people think it is the key fob being close by so i'll keep it further away and inside a tin or something. Not the end of the world as long as I can figure it out and don't have random dead batteries anymore.

Thanks for the input from everyone so far.
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The manual almost blatantly says there is a dark current drain issue with the fob. Also, again, disabling the fob takes about a million times less work than dealing with a dead battery. Saying it is not worth a try makes absolutely no logic sense.
LOL, the OP is free to do as they wish, just as I'm free to express my opinion. I confess, I haven't read the manual in a few years. It "almost blatantly" says what, exactly? I'm guessing you mean this:

Never leave or store the access
key inside the vehicle or within
6.6 ft (2 m) around the vehicle (e.
g., in the garage). The access key
may be locked inside the vehicle,
or the battery may discharge
rapidly.


This only pertains to leaving the fob in close proximity to the vehicle, which is not something the OP has consistently done. The TSB for dark current is a little more generous, requiring the fob to be kept "at least 10 feet away to allow the system to go to sleep". Once again, bringing it inside with you should be sufficient unless you have an attached garage and leave the key against the wall (which I still doubt is a problem since the transmitter is very low power).
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The manual almost blatantly says there is a dark current drain issue with the fob. Also, again, disabling the fob takes about a million times less work than dealing with a dead battery. Saying it is not worth a try makes absolutely no logic sense.
LOL, the OP is free to do as they wish, just as I'm free to express my opinion. I confess, I haven't read the manual in a few years. It "almost blatantly" says what, exactly? I'm guessing you mean this:

Never leave or store the access
key inside the vehicle or within
6.6 ft (2 m) around the vehicle (e.
g., in the garage). The access key
may be locked inside the vehicle,
or the battery may discharge
rapidly.

This only pertains to leaving the fob in close proximity to the vehicle, which is not something the OP has consistently done. The TSB for dark current is a little more generous, requiring the fob to be kept "at least 10 feet away to allow the system to go to sleep". Once again, bringing it inside with you should be sufficient unless you have an attached garage and leave the key against the wall (which I still doubt is a problem since the transmitter is very low power).
The more you talk, the less it makes sense.

I have literally been disabling my fob every time I exit for the past month. The total sum of my effort disabling my fob was LESS work than you spent on your last post. Yet your position is, “Not worth the try!”

The manual also states in bold text, to help save the battery, the remote access should be disabled if the car is going to sit for awhile. Subaru is basically saying there is a dark current battery drain for a normal functioning Outback. It is all related to the fob, the sensors, etc.
I have not had the parasitic draw checked, i live 1.5 hours away from a dealer so it's not easy to get work done. I'll look into this test and see if i can do it myself or have someone nearby do it.

I drive it 3-4 times a week, with trips varying from 5-20 minutes mostly. I also use it anytime we go on a longer trip so 1 hr+ every other week or so. I have driven my other car <5 min to work every day for a year on the original battery with no issues...I know it's irrelevant but I think there is a bigger issue than the length of my trips...
Ok, sounds like short trip driving certainly could be a significant factor for you. I know you're out of warranty, and that TSB is pretty involved (not sure what a dealer would charge for it), so if you have a multi-meter, it may be worth disconnecting the negative cable from the battery and putting the meter in there to read the current (in case you're not familiar, this looks like a proper procedure: https://www.wikihow.com/Find-a-Parasitic-Battery-Drain). I've tested my parasitic draw with a high sensitivity clamp meter (capable of reading in the milliamp range without disconnecting the battery) and found that the car sleeps within a minute or two of locking it.
The more you talk, the less it makes sense.

I have literally been disabling my fob every time I exit for the past month. The total sum of my effort disabling my fob was LESS work than you spent on your last post. Yet your position is, “Not worth the try!”

The manual also states in bold text, to help save the battery, the remote access should be disabled if the car is going to sit for awhile. Subaru is basically saying there is a dark current battery drain for a normal functioning Outback. It is all related to the fob, the sensors, etc.
Good grief, you feeling ok man? My manual doesn't say "awhile", it says "when the vehicle is not going to be used for a long time" or "an extended period of time". I take that to mean a week or more, which would not really apply to the OP, who drives it somewhat regularly. But, like I said, the OP is free to try it if they don't mind the loss of functionality, but I, personally, don't see it as a worthwhile trade off. This has nothing to do with the time it takes to perform whatever wizardry is required. ;) FWIW. YMMV. Sheesh.

One thing's for sure, disabling keyless access is not going to completely kill the parasitic draw, or force the car to run the alternator more frequently.
I think I have read the FOB should be 20 feet away. Now throw some home walls in there and the distance may vary.

Throw a charger on it periodically is about all I can suggest really otherwise.
I've moved my fob farther back in the house, b/c next to the front door may be a tad too close with car parked out front. Just had same problem: went away for 1.5 week (in another vehicle) and '14 Outback's battery was dead when we got back. Mechanic is checking it over and looking to rule out other causes, but my next door neighbor had same issue with his '16 Outback and recommended storing the fob(s) in a Faraday bag or aluminum foil. Even in the house? OK, then… and I guess it's a good thing I've saved several mint tins as well. LOL
Maybe the 2019 Outback is different or maybe the Australian spec cars are different, but my load current tests shows that the key fob has no affect at all on the battery load once the vehicle & fob stop two-way communication after 10 minutes (LED on the fob stops flashing). The current drops to 11.8mA with quick pulses every now & again up to 18mA, the same as with the key at the other end of our house or put inside a metal container (Faraday cage). A good quality analogue meter in series with the battery cable shows this.

Two-way communication between the vehicle & fob is roughly within 2m of the vehicle, possibly a bit less. Further than that the remote will be out of two-way communication range but the remote fob will still lock/unlock the doors up to a considerable distance (at least from the other end of our house through four interior walls, & no doubt much further).
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