For an older non M car, I recently got this one because it seemed well received by others.
I've only used it once or twice and no complaints.
I'm a little suspicious of the dealer when he tells me my problem is I don't drive the car enough. To me that sounds a lot like: "I don't know what's wrong."
Remember, too, that when the battery gets low, you'll get a message on your dash (or screen). At least, I did. There should be a reference to that in the manual.