Here is a tip. Once I set in my X5 with the ignition turned off and key removed. It's interesting that the Navigation DVD player was waking up here and there. This obviously drains the battery. So, I remove the DVD disc whenever I don't get to drive my X5 for few days. Worth a try.

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2011 BMW 740i
2011 Toyota Sienna Limited
2008 X5 3.0 Space Gray (sold)