Q: battery drainage on 2006 BMW 325xi

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I have been having problems with the battery failing. my car randomly won't start, regardless of the outdoor temps. This has been happening more frequently. The dealer keeps telling me that when they test the car the diagnostics indicate that I am not driving the car often enough. I drive to work, doctor's appts and do errands on the way home on a daily basis. The car never sits idle for more than a day. The checked for a draw, but have found nothing wrong. I have read about possible causes such as radio, navi system, fan, etc. Are there any known issues that can cause this problem? What do you suggest to check for a parasitic draw? Thanks.
(1) Answer
to check for a parasitic draw try disconnecting the battery overnight and see if when reconnected the car starts fine. if you can, measure the voltage to see if it went below 12.5v. if it still lost power it will need a battery. batteries can drain internally too!