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Changing Battery in the Key???

220K views 39 replies 21 participants last post by  Helsie99 
#1 ·
The battery is running low on my Mini key (2004 model) its becomming so bad that i have to stand next to the car to open it! I know how to open the key and change the battery. The question is: Will it still work after?
I have heard that you have to take it to the dealer to get the battery changed, because it "flashes" the key and it will no longer work on the car. Is this true? if so, how much will this cost?
I do have a spare key which works, but to be honest, its in perfect condition and i dont wanna use it unless i need to e.g. i lose the other key or something.
 
#37 ·
Opened up the key again just to check the voltage to see if the voltage went up from 3v, it's still at 3v after a few trips, I don't have to drive very much as I work from home, but I imagine the voltage would at least be around 3.30v at least. Not sure what voltage these batteries top out at, just wondering if stick the key in the ignition slot without pressing the the start button, if the key will still charge or does ignition have to be on?
 
#38 ·
Opened up the key again just to check the voltage to see if the voltage went up from 3v, it's still at 3v after a few trips, I don't have to drive very much as I work from home, just wondering if stick the key in the ignition slot without pressing the the start button for the acc position, if the key will still charge?
I doubt it, but I don't really know for sure
Only one way to find out (seeing as you've now become the expert on this subject) :p
Measure the voltage on the battery as you insert the fob into the slot, then switch on ignition after around 1 minute
 
#39 ·
Hello I know its a few years since this post started but I was having the same problem with my 09 cooper circular mini key fob (3 button) :( The key just suddenly stopped unlocking/locking the car last night. The spare also doesn't work - or charge, (possibly as I've never used it!). I tried driving around with spare in ignition today for about 20 mins but still Nada. How long will this take to charge if not already dead? I can drive with both so that's OK but I can't lock it as it sets off the alarm when I unlock it manually (even though this is not for long, its deafening!). I just wanted to ask about the 30 second rule - if I tried to do it myself and took longer than that - what would happen? And has anyone tried www.keyfobrepair.co.uk in the UK? As Dealer is asking for £170 for the fob. Thanks!
 
#40 ·
Hello I know its a few years since this post started but I was having the same problem with my 09 cooper circular mini key fob (3 button) :( The key just suddenly stopped unlocking/locking the car last night. The spare also doesn't work - or charge, (possibly as I've never used it!). I tried driving around with spare in ignition today for about 20 mins but still Nada. How long will this take to charge if not already dead? I can drive with both so that's OK but I can't lock it as it sets off the alarm when I unlock it manually (even though this is not for long, its deafening!). I just wanted to ask about the 30 second rule - if I tried to do it myself and took longer than that - what would happen? And has anyone tried www.keyfobrepair.co.uk in the UK? As Dealer is asking for £170 for the fob. Thanks!
I read somewhere else on here about charging the key on a toothbrush charger base - so tried it - and I think that might have revived one fob. Hoorah. Will check again tomorrow. Thank you for all the people who posted about that!
 
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