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DIY: replacing key fob battery

617K views 477 replies 246 participants last post by  Shonky 
#1 ·
Ok so here is my first attempt at a detailed "DIY" thread, also if you mess up your own key trying to do this don't yell at me!:argue:

So I have the 2 key fobs that came with my car when I bought it used. One I use everyday and the second one has had a dead battery since I got the car. When I called the dealership they wanted like $260.00 for a new one. I did a search around here and found you could get deals and what not and possibly get it down to around $90-120 bucks.. still way too much in my book since I already had a working key.

After seeing a thread on here where another member had taken apart a key fob from a car he had already sold I decided what the hell the key was already dead anyways...

Here is the key before I tried anything..



I then proceeded to take a matt knife and xacto knife and basically carefully cut the key open along the seam where the top and bottom joined up.



Next I took a small chisel and broke the spot welds on the battery that connected it to the rest of the circuit board.



Once I had the battery out I looked at it and took the model number "a panasonic VL2020 3v" I found the exact same battery on mouser.com for $4.73. Once I got the battery is was a simple matter of soldering the new one in and making sure everything fit back together.




Before I glued it up I rubber banded the thing together and went out to my car to see if I could program it.

Put the working key in the ignition. Turn to position 2 for like 1 second then back and remove the key.

Press and hold the "unlock" button then press the "lock" button 3 times, you should hear all the locks cycle through.

Now take the non working key and press and hold the "unlock" button then press the "lock" button 3 times.

Then turn the ignition on and off again to end the programming....

I took the car for a drive to charge up the battery. Once I was certain it was all working I glued up the key again with some super glue....

Here is a pic of the key being glued...



While definitely not a hard or complicated "DIY" project I did save myself about $200 and had fun while doing it...
 
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#4 ·
dude, that's fresh, you're the freakin man and will probably save more than a few people hundreds of dollars!
 
#6 ·
#7 ·
More mAH means the battery has more capacity and will last longer (esp between charges).

As for voltage, in this case, it's possible that increased voltage will provide extended range but it's also possible that you'll damage the electronics of the key, depending on how sensitive they are. There's usually some protection for things like this but the key is made from a closed-case and not meant to be servicable so who knows. 3V ain't much and it *most likely* wouldn't hurt to increase it a bit but I would stick to the stock battery to avoid killing your key....
 
#8 ·
Yeah I am thinking the poor range might be from the battery charge drooping quickly (due to low mAH) so a little higher on that would help fix that.....

Then a little more voltage would help with range...

I would assume there is some safety factor engineered into the design so .5 volts more should hurt it too much,

and when you unlock the door your taping the button its not like your holing it with another 3 volts going through the circuit for 5 min...

The key I use the most is getting work out and crappy looking so I might give it a shot on that one...
 
#10 ·
Yeah no prob I will start a new thread with a DIY if it works and doesn't blow up....HeHe
 
#13 ·
The metal tabs are spot welded on, and I just soldered the new tabs to the old ones. I did have to putz with bending the tabs to get them to line up with the ones on the battery.... Make sure you get the positive + on the battery going to the positive + on the circuit board!!!
 
#15 ·
Already opened the key (made a little mess but i'll solve it later)..

anyway..

for pure personal sake i've tried with a tester to check if the battery is really drained

..full charge..

in fact the remote works 1 time on 100 try..

anyone knows if it might be related to the reciever into the mirror?
 
#23 ·
do i really need to glue it back together also ...
 
#25 ·
I tried replacing my battery last night, I soldered it on and went outside and tried unlocking my car, it worked! funny how the key didn't reset or anything, all I had to do was replace the battery and thats it. but when I added the glue, I put a couple of weights on top of the remote so that it was shut tight, I guess the buttons were being pressed also, and this morning.. guess what, it doesn't work. im trying to figure out what happened
 
#26 ·
EDIT: just went to radio shack, tested out the battery and it came out dead..............

last night it was working, but I guess all those weights on the remote (and it was near the car, from the inside of the house) drained the battery.

do not put weights or hold the case tight while pressing any of the buttons overnight
 
#36 ·
i still haven't glued mines together, its taped up with clear tape, last time i valet my car i lost my ticket, and told the guy its the key thats sealed with tape hahah

just make sure when you glue it, don't put anything heavy on top so that the buttons don't get pushed, otherwise the battery will die
 
#37 ·
Dude, I was about to pay $200 for a spare from the stealer since my key only works if I hold it right up against the roof and press the button once. After I press it once, it won't work again until I plug it in and it charges up a tiny bit again.

Just ordered two batteries, just to have a spare!
 
#42 ·
Damn, I almost had to do this because I though my key stopped working. I did the procedure to re-sync the key with the car and it works like a champ now :thumbsup:
 
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