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According to google, the battery us at 75% when it's at 12.4V. I realize this is measuring the battery under load, but I'm totally stock and I don't have any alarms or ancillary stuff that would be draining the battery.

I read somewhere that I should wait until it's 12.4V before shopping for a new battery. What do you all think?
 

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Tables like this one show how battery voltage changes as state of charge decreases

100% 12.70+
75% 12.40
50% 12.20
25% 12.00
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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Battery voltage can only be properly measured when / while disconnected. The installed BMW battery is ALWAYS under load - ALWAYS. The BMW ECU measures State of Charge by counting the electrons into and out of the battery, the IBS is a Coulomb counter.
 

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3 voltage data points:

12.15 V 2014 328i .... hope to get another year out of this

12.45 V 2017 328i ..... no worries

12.04 V 2009;328i ..... the second battery was installed 4 years ago ... maybe another year or two left?
 
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