I doubt they would be able to test it properly and that they would do anything at all without a receipt anyway but you never know. There still is a very small chance I guess that you have something going on with the car so maybe keep an eye on that anyway. It might be a good idea to check voltage right at the battery if you aren't already.

Mine was charging at just under 15v (at the battery) when I checked it yesterday which I found a bit surprising but that was in in a fairly warm car.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)