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BMW 330ci Chronic Dead Battery

I have a 2006 BMW 330ci. I purchased it in Feb 2008 with a clean maintenance record. I’ve only put 2000 miles on it since Feb 2008. For the second time since I purchased the car, I left it sitting for 2 weeks without starting it and it completely died. Not even my key remote worked!!! The first time it happened the dealer replaced the battery and said the car was otherwise fine (checked alternater, etc). The second time they put in a larger battery (yellow top) and are telling me I need to start the car every now and then(which gets complicated when you fly around the country for a living) or hook it up to a trickle charger. They are telling me that even when the car is off it’s electrical components are checking on each other (13x an hour) and draining the battery. I can’t believe this is normal and that every BMW in the world has to be started once a week to not drain the battery dry. So my question is do I need a car sitter when I leave town? Should I have bought American? Or is there some other thing going on?

The dealer is correct in that the car’s electronics are active even if the vehicle is parked, but I do not agree that they should drain a good battery in two weeks. You should be able to walk away from this car for a month or more and not worry.

You’re not the only BMW owner who accumulates mileage slowly.

If the warranty is still in effect, and I assume it is, keep going back to the dealer until this is fixed. It’s not normal.

Having said that, and in case the warranty has expired, rather than spend tons of money trying to figure out what’s causing this problem, you could buy a Battery Tender for a few dollars, and hook it up to your battery when you are away.

A Battery Tender is NOT a trickle charger, and don’t let anyone sell you one of those. NO TRICKLE CHARGER. They will overcharge the battery and shorten its life. Tender, yes, charger, no.

I use a Battery Tender Jr. for the car I don’t drive over the winter, and it works flawlessly.

BMW. The Ultimate Driving Machine. Assuming you keep driving.

If you did by American whats the BMW’s equal?

There is really no American equivalent to a BMW, for better or worse. Cadillac has a CTS? which emulates the mid to higher range BMWs.

Our 2004 330i has set for several weeks at a time with no perceptible weakening of the battery. Yes, you do have some systems still active with the car off, but the amount of current they draw is minuscule and the battery should hold for months, not weeks.

I have a '97 328 in storage right now that will be there for 10 months, and I am confident that it will start right up when I go to get it out.

It is tougher to find electrical drains on new cars than it used to be, but the dealer can find the problem if you keep after them.

You can start with the easy stuff - have you added any aftermarket electronics? Any chance the trunk or other courtesy lights are staying on?

For a 3-series, I would say the closest US equivalent would be a Mustang Cobra. Rear wheel drive and fully independent multi-link suspension, etc. Last time I checked, a Cobra cost as much as a 3-series.

That being said, and though there is a Cobra in town that I have secretly lusted after, I own three 3-series BMWs and I have never seriously considered a Mustang, so perhaps it is not completely equivalent…

MC has it right. I would only add this. Get the comment “They are telling me that even when the car is off it’s electrical components are checking on each other (13x an hour) and draining the battery.” and that it should be expected after only a week, in writing. I’ll bet they will not do it. If they do take that to the regional offices and see what they say. It should be interesting.

I will also suggest that it may well be the charging system as well as the battery or an unusually high dark drain (too much electrical usage when off).

NOTE: Worth repeating “A trickle charger is not a battery tender.”

Thank you very much - it’s such a frustrating situation. I hear you loud and clear…BATTERY TENDER ONLY!