Quote:
Originally Posted by BMW003E
Good question. Usually, the batteries in my key fobs last years. I keep them more than ~12 feet away from the car when at home. I did have the battery in my fob go dead (got the same warning as you) right after I picked up my car from the body shop (I got rear-ended on the way home from work). My guess is that the left the key in the car for the almost 2 weeks the car was at the shop, which drained the battery.
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I had to replace the battery in my key fobs 5 times in the first 13 months of ownership. After the first 2 replacements I kept the key fobs further away from my garage parked car and it did not make any difference.
I think this is a software issue and reported it to my dealer each time I had to (prematurely) replace the battery. I measured the voltage of the new and old batteries each time, as I am a retired Electrical Engineer and possess accurate multimeters. This is what I found; when I removed the old (so called depleted) battery it measured very close to 3.0v each time. A new 3.0v CR2032 lithium battery measures about 3.3v. Clearly, the warning in the car should not come on until the battery is very much more depleted than 3.0v. My guess is that the warning should not come on until the battery has depleted by at least 20% of its rated voltage, i.e around 2.4v.
However, since my car software was updated to version 07/2020.05 in July I have not experienced any more problems with the key fob batteries. Hopefully, this software upgrade fixed the problem.
