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Quick PSA About Changing the Key Fob Battery & "Key Fob Battery Low" Error Message

Ostrichsak

Active Member
Sep 6, 2018
3,394
3,394
Colorado, USA
If/when you get the "key fob low battery" I would recommend the following as best practices:

1) Change not one but BOTH (or all three if you got a 3rd) batteries at the same time. They should last about a year and (if you buy them right) they're not super expensive. I found that you can get 4 Duracell or 6 Energizer for about $6-$8 at your door step the next day. Walmart is absurd at like $5 for a single battery.

2) Change the batteries WHILE SITTING INSIDE OF THE CAR! (more on this later)

3) Sit with all fobs inside of car until "key fob low battery" message clears. Sometimes a MCU reboot can expedite this process if it's not happening right away. Patience is usually quicker.

4) Make SURE you get good batteries. I can't tell you how many issues I had years ago when I thought I had Energizer batteries that were brand new. After much volt meter testing and research I determined that counterfeit button cell batteries is actually a pretty common problem. The "new" batteries actually tested at a lower voltage than the "old" batteries when I put a multi-meter on them. Prior to this, I thought I had dead fobs though as none of the batteries I bought worked.

5) Sometimes if you get an error you can hold down the middle button (roof) of both fobs while standing outside of the car to get them to actively re-establish comms with the MCU if passive isn't working. (You likely will never need this one but something to try if you're having issues and have tried everything else)

Much of what I stated won't be a problem even if you don't do it exactly most times you go through this process. Until it is. This was my recent interaction with #2 above. I've gone though this dog & pony show multiple times across half a dozen different cars now and really it hasn't been too much of an issue. I even ignored some of the manual's instructions on some changes (most notably the changing of both batteries at the same time) without any negative effects. Like I said previously, the lion's share of the time time you'll be okay and nothing negative will occur.

I had an issue I just finally fixed that I thought I was going to have to contact Tesla (**shudders**) to resolve. The primary fob was basically dead to the car. I used several batteries (which I tested both with a volt meter and in in 6 different fobs across three different cars) and swapped them around countless times. I wasted hours. The final verdict was that this one fob was dead since batteries that worked in other fobs didn't work in this one. I genuinely though this fob was toast and I was going to have to buy a new one. I couldn't lock/unlock or get any of the prox sensing to work. Nothing. I researched tons of stuff online and nothing I tried resolved the issue. I literally wasted hours of my time the last couple of days trying everything in my power to not get Tesla involved.

Then, I read something about changing the batteries while sitting inside of the car. Something about when the fob first wakes up the car will recognize it. Even though I was doing all of my battery rodeo in the kitchen just inside the garage door so my back and forth after putting different batteries into it was pretty quick I decided to give it a try. I had tried everything else to include brand new Duracell batteries (being bought from seller:"Duracell" on Amazon and delivered today) and this seemed simple enough so... why not.

I took the new Duracell battery (measured 3.3-volts on the meter prior to install) and the fob out to the car along with the small flat-head screwdriver I had been using. I sat in the car with both fobs, changed the batteries and within moments the "key fob battery low" warning that had been on display for the entire time went away. I got out of the car and pressed the lock button the "dead" fob and surprised to see that the door handles retracted and the lights flashed. It locked! I then double pressed and bam! Handles presented and lights flashed. As a final test I took the 2nd fob back into the house and approached the car with only the "dead" fob in my hand. I was ecstatic when the handles presented and the car greeted me just like nothing had ever happened.

tl;dr Change your fob batteries while sitting in your actual car to avoid LOTS of grief. HTH
 
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ShawnA

Supporting Member
Nov 13, 2017
936
681
Edwardsburg, MI
Hi Ostrichsak,

I have certainly duplicated your bad battery experience with Amazon...

Others recommended trying Batteries plus bulbs...
What a clusterfest that was...
Freight free to the local store and the price looked OK.
It was like a bad trip with your kids - Are we there yet???
Three or four calls later and a week or two they did say they were on hand.
When I arrived and the manager took 15 minutes to find them...
I was so disgusted that I only saw when I got home that they were the
wrong battery...

Good prices, fast delivery, fresh batteries - Try Digikey.com

Shawn
 

Ostrichsak

Active Member
Sep 6, 2018
3,394
3,394
Colorado, USA
Hi Ostrichsak,

I have certainly duplicated your bad battery experience with Amazon...

Others recommended trying Batteries plus bulbs...
What a clusterfest that was...
Freight free to the local store and the price looked OK.
It was like a bad trip with your kids - Are we there yet???
Three or four calls later and a week or two they did say they were on hand.
When I arrived and the manager took 15 minutes to find them...
I was so disgusted that I only saw when I got home that they were the
wrong battery...

Good prices, fast delivery, fresh batteries - Try Digikey.com

Shawn
Good option. I haven't ordered batteries from Digikey but I have placed a lot of orders with them over the years (decades?) with good luck. I, too, have had horrible luck the couple of times I tried to use Batteries+ so I don't even consider them a source any longer.

My personal experience is that if you're going to buy from Amazon make SURE the the seller is the brand name and not some 3rd party seller. If it's a 3rd party seller don't buy no matter how good the deal or reviews make it seem. They're cheaper because the probably counterfeit. Brand name (Duracell or Energizer) 10-year shelf-life for $6ish and free Prime delivery the next day it's going to be difficult to compete with that.

I think I saw that Tesla recommends Panasonic but the key is just getting a quality name brand with a known source and you should be good to go.
 

ShawnA

Supporting Member
Nov 13, 2017
936
681
Edwardsburg, MI
Hi Ostrichsak,

A double check for me (On the Panasonic X CR2354) was $1.33 each at Digikey
plus $8.99 shipping Fedex Ground. So, even with the freight not bad.
I bought 4 batteries for my 3 fobs.
Keep Digikey in mind...

Shawn
 

Ostrichsak

Active Member
Sep 6, 2018
3,394
3,394
Colorado, USA
Hi Ostrichsak,

A double check for me (On the Panasonic X CR2354) was $1.33 each at Digikey
plus $8.99 shipping Fedex Ground. So, even with the freight not bad.
I bought 4 batteries for my 3 fobs.
Keep Digikey in mind...

Shawn
For two, that's still about double what you'd pay for 4 Duracell or 6 Energizer 2032's from Amazon and they'd arrive the next day. Assuming you have Prime, or course. Both of these are sold by the actual manufacturer on Amazon for that price. No 3rd party to wonder if it's a scam or not.
 

bmah

Moderator, Model S/X, California Forums
Mar 17, 2015
3,945
7,110
Lafayette, CA, USA
Protip: When removing the old battery, be careful not to bend or break the battery contacts. Ask me how I know about this. :mad:

Bruce.
 

Ostrichsak

Active Member
Sep 6, 2018
3,394
3,394
Colorado, USA
Protip: When removing the old battery, be careful not to bend or break the battery contacts. Ask me how I know about this. :mad:

Bruce.
Thanks for the reminder! That was another thing I wanted to add and totally forgot. Sadly, I can't edit my first post to reflect this so hopefully people read to at least post #6.

To elaborate, make sure that what you wedge under the battery to pry out doesn't go underneath because the negative contact is of bad design considering that's where you pry and it's really easy to push a small screwdriver too far underneath the battery which will basically pry under the thin battery contact that resides underneath in an example of a bad design with an easy correction. If they had extended that contact piece away from the battery under the housing you wouldn't be able to get under it prying out the battery. Sure you may scratch it a little bit but you couldn't get under it to pry it out which seems all-too-easy to do and I came real close.
 
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