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Key battery replacement

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Debell192
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Key battery replacement

Post by Debell192 » Sat Oct 09, 2021 6:59 pm

If you have the diamond shaped key and it’s not unlocking or locking the car you may need to replace the internal battery.

It normally charges as you drive the car but if the battery is worn out it won’t hold the charge as well.

Here is a video showing you how to complete.

https://youtu.be/FLluLorD3yo
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MalNCH
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Key battery replacement

Post by MalNCH » Thu Oct 14, 2021 5:21 pm

I need to replace mine so I ordered from the ebay link in the video, they have just arrived and they are the wrong batteries FFS, the ones in the link have the contacts opposite each other so they don't fit, you need the ones offset at 90°. The new ones the guy is using are offset correctly, he's put a link to the wrong ones.

EDIT: The link has just been changed to the correct one as I left a comment about it on Youtube.
Last edited by MalNCH on Thu Oct 14, 2021 5:42 pm, edited 1 time in total.
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buzyg
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Key battery replacement

Post by buzyg » Thu Oct 14, 2021 5:23 pm

MalNCH wrote: Thu Oct 14, 2021 5:21 pm I need to replace mine so I ordered from the ebay link in the video, they have just arrived and they are the wrong batteries FFS, the ones in the link have the contacts opposite each other so they don't fit, you need the ones offset at 90°. The new ones the guy is using are offset correctly, he's put a link to the wrong ones.
Thanks for the heads up I should probably do mine.
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MalNCH
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Key battery replacement

Post by MalNCH » Thu Oct 14, 2021 5:34 pm

buzyg wrote: Thu Oct 14, 2021 5:23 pm Thanks for the heads up I should probably do mine.
It's obvious when you compare the battery in the vid to the ebay linked ones but like a mug I just assumed he'd linked the correct ones! So that was £13.58 wasted.
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axelleveau
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Key battery replacement

Post by axelleveau » Fri Jan 14, 2022 9:30 pm

I was going to start a thread of my own but figure out I might as well post here as I just took appart one of my keys. The goal will be to add some pictures and advice about the battrey replacement and also about the button replacement.
I have one the two keys which I received with my car that is very lazy on locking the car. I am used to play with a soldering iron so decided to open the first key, confirm the situation and order the batteries for both keys.

Part 1: Opening
As far as opening goes, I started at the back end, took multiple passes with a scalpel and then with a cutter. I then used a plastic pick and then a spoon (was easily available at the time) to start separating the two halves while finishing the cut. I would only recommand taking your time to avoid slipping and either damaging the case or a finger (one of them heals at least :fuelfire: )
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Part 2: Diagnosis
I wanted to confirm battery and buttons status. Measure battery sitting at 3.00V which is not bad BUT when pushing buttons it fell to 2.65-2.7V telling me it is likely struggling to deliver current and at this stage replacing the battery is not hard so I might as well do it. One thing I noticed though is that the lock button did not produce such effect. So I decided to measure resistance across each button whitout and with pressing on them and realised the lock button does not seem to do anything. In order to confirm it is indeed the button itself functionning I shorted two of its legs while measuring the battery voltage and measured a voltage drop telling me the button is in fact dead.

Part 3: The issue
I have seen kits on ebay with a battery, 3 buttons and a blank case/key (I guess for people who want to refresh the case too?). My issue is all the kit seem to include 3 of the same buttons, long ones with a leg at each end (blue circles). For some reason, my key has the lock button being square with a leg at each corner(red) and not pads for soldering a long button instead:
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As far as I have seen in pictures online, all the diamond keys seem to have the long buttons while other BMW keys have 3 square buttons but none of them have this mix. Also, my key has some glue on the charging coil which I also have not seen on any other.

I ended up ordering two batteries on their own and a kit of Surface Mounted buttons on the side. The kit has the two type of button I found in the key and a lot of other sizes so it will complete my collection of handy electronics.

Next part should be in about a week once I receive everything. I already mounted a fine tip on the soldering iron so it's ready to go.
Gone - Ford Ka MK2 Petrol - Black
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Rucky
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Key battery replacement

Post by Rucky » Sat Jan 15, 2022 12:33 pm

Whilst I do all the DIY on my Z4 I leftbthe key refurb to the experts. Prices here are very keen so fitting your own battery etc only saves a few quid.
https://www.themasterlocksmith.com/prod ... key-blade/
I have used this guy twice to refurb Z4 keys with new blades and cases switches etc.
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axelleveau
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Key battery replacement

Post by axelleveau » Fri Jan 21, 2022 1:02 pm

Part 4: Removing parts
I received the replacement batteries and switches and confirmed they fit:
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I then started by removing the battery so I can do the rest of the work without any power on the board. This is the easy part.
Removing buttons in a much harder task, especially the middle one which has 4 legs. As I do not have a hot air soldering station, I took my time and heated up legs one by one while lifting a tiny amount to make sure I did not tear a pad off the board, and repeated going around the button until it got free. I still lost a couple of pads on the lock button on both keys but they were not use for carrying current.
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Part 5: Putting it back together
This was an easier task. I put a dab of glue under each switch to make sure they stay in place as the pads where pretty fragile/missing, then held the switch down with a pair of tweezers and applied solder.
The battery was straightforward to solder but the legs needed massaging to make sure the battery was flush with the board and fit in the case.
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I then cleaned the cases with soapy water and a toothbrush, dried them and used sand paper to clean the mating surfaces before gluing.
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Part 6: Bonus
As the glue leaves not very pleasing white marks I decided to lightly sand down the area and then apply some of the carbon vinyl I recently bought to cover the interior of the car. This way the keys will match the car. I am not perfectly pleased with the result as the shape is very complicated to cover and I ended up with wrinkles. I might redo it in the future but for now it will do and I have two perfectly working keys :)
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Gone - Ford Ka MK2 Petrol - Black
Will hang around to carry materials/people and in emergency - Ford Fiesta MK7 1.0 Ecoboost - Black, white rally rims, white decals, remapped
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axelleveau
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Key battery replacement

Post by axelleveau » Fri Jan 21, 2022 1:07 pm

Rucky wrote: Sat Jan 15, 2022 12:33 pm Whilst I do all the DIY on my Z4 I leftbthe key refurb to the experts. Prices here are very keen so fitting your own battery etc only saves a few quid.
https://www.themasterlocksmith.com/prod ... key-blade/
I have used this guy twice to refurb Z4 keys with new blades and cases switches etc.
I definitely would recommend using a service like you quoted to anyone not experienced in small sodlering work. For me it was more of a project and challenge so did prefered to DIY but clearly the price they charge is fair for the amount of work and skill required :thumbsup:
Gone - Ford Ka MK2 Petrol - Black
Will hang around to carry materials/people and in emergency - Ford Fiesta MK7 1.0 Ecoboost - Black, white rally rims, white decals, remapped
Now - Z4 Coupe - Montego Blue: Here

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RexxNoggin
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Key battery replacement

Post by RexxNoggin » Sun Jan 28, 2024 5:32 am

My Z is going on 17, and I seem to have to get closer and closer to operate the door locks. I asked about battery replacement, and the Dealer just said that, "it is recharged by the car, when plugged in." But he, " would be happy to get a new set if I liked..." (the estimate was about $1000 US for two!!! :cry: ) This was my wife's car, and she often only used one of the keys. So, this left one key, uncharged. I guestimate that it would be wise to rotate off the keys, as used? As I understand this, the case is glued shut? (This is why I am unable to pop it open? ) Was there a particular type of glue that should be used to reseal the fob? Also does any one know of lock smiths in the States that do this sort of repair? :roll:

Well, new developments: I tried the local key smith in Ocala. They smiled, and said, "Good Luck With That! Try the BMW dealer!" I emailed Ocala BMW. They told me "come on down, $10 @". (I was suspicious, a female had answered from the service department.) I sent her all the data again, and pictures of the fob. No reply. I stopped by (about a 40 min drive for me) today. Service guy raised both hands and said, "No way! Too many things go wrong with that battery replacement repair!" My comment was "Well I thought German Engineering was supposed to be the best! Perhaps it is not the best for me! Key fobs you cannot easily replace the battery in? And, what brilliance was no dip sticks?" His reply, "We agree with ya on the dip sticks..."

Ok, 'nuff rant! I pried one open today and ordered some batteries from Amazon, at about $12 each VL 2020, I needed to watch for the electrode placements, not all VL 2020's are the same...
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