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Old 09-05-2012, 11:16 AM
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FrankAZ FrankAZ is offline
Liverpudlian at heart
Location: Chandler, AZ
Join Date: Feb 2009
Posts: 526
Mein Auto: 2009 328i Sedan
Originally Posted by ajm8127 View Post
I just popped the battery door off of my FOB and noticed the battery was a CR2025 size 3V watch battery. To the best of my knowledge, these are primary lithium cells which CANNOT be recharged. I was also told by the sales man that putting the FOB in the slot should recharge the battery. I really can't see how that is the case. There are some rechargeable batteries in a CR2025 case, but the one I have is definitely not one of those.

Bottom line: Pop the battery cover off your FOB. Check the battery. If it does not specifically say it can be recharged, or if it does not say "Lithium Ion", then get a new CR2025 battery and try that.
If the battery is a CR2025 then it is NOT rechargeable. If it is a LIR2025 then it is rechargeable.

CR designates 'manganese dioxide lithium' chemistry which is not rechargeable. LIR designates a chemistry (variable types) which is Lithium Ion based and rechargeable. The first two digits ('20') indicate the diameter in mm, and the second pair of digits ('25') the thickness in tenths of mm.

I'd be curious if a BMW supplied from new non-Comfort Access fob had a basic 'CR' non-rechargeable battery since that contradicts in the most absolute sense with their manual's notification that the fob recharges while it is in the slot. Someone in BMW's tech pubs or more likely their fob supplier messed up.

ED Vehicle: 328i Platinum Bronze / Beige / Light Burl | Sports (paddles) | Premium | Auto | Navigation | Fold-down seats | Alarm | Comfort Access | iPod integration.
ED Tour: 1st June - 13th July 2009. (Route map).
ED Progress: Delivery of M1100Z on 2nd June 2009; Drop off at Geneva 13th July; The journey home on 'Ryujin'; Redelivery 19th September.
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