If your car is new enough to have a registered battery, you can use a level two scanner like nt-510 and it will show the charge history of the battery, example the past five days each day the average charge

The battery I just replaced worked perfectly fine until one day the car wouldn't start. When I scanned the battery module it showed the past five days average of less than 45%. The total life histogram also showed way too many hours in the 20-40% range.

If you can read that info it make it painfully clear the state of the battery

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)