Dead Battery/Drain
 

Last winter I had trouble starting the car after only a few days in our heated garage... MB replaced the battery under warranty. Did not find any other problem.
This winter it would not start after 5 days parked at the airport. Mind you it was cold maybe -15C but my other cars never have a problem starting

Then twice since then it would not start. Today it was completely dead. I had to use the mechanical key to open it. And I drove in 2 hours 3 days ago.

I have read the threads regarding blower motor staying on, one thread claiming a bad battery cable, another with some bad module under the steering wheel.

Any other people with this problem?

My 08 had a similar problem. Sometimes it's the rear lift gate module which stays on even after the rear hatch closes. Also, the locking plate for the rear hatch might have to be adjusted.

Get it diagnosed at your dealership, hope you are still under factory or extended warranty! There's definitely a draw coming from somewhere.

Good luck.

We found a dead battery in our 07 R500 a few weeks ago in warm weather. The car hadn't been driven in about two weeks. The battery is less than a year old. I called roadside assistance and had it towed to the dealer for some warranty love. They had the car for 10 days and couldn't find a draw. They also said the battery checked out fine.

Fast forward a few weeks. This past weekend it was deja vu. Only this time the car hadn't been driven for one week. This time it wouldn't respond to jumper cables or a trickle charger. So, another call to roadside assistance. All they did was jump it with a portable battery but the POS did start.

They also told me that contrary to urban myths on this website, Mercedes roadside assistance WILL NOT replace a battery on an R500. They said to schedule an appointment at a dealer. The dealer said 2 hours to replace a frickin battery! That's ridiculous. Any design that requires a skilled technician to spend 2 hours replacing a battery is a poor design.

So, the dealer will not be replacing the battery. Sears sells an AGM equivalent for $145 (US). Mercedes will however be getting the car back to find the source of the current draw. No car battery less than a year old should lose all of its charge in seven days in 80 deg F weather.

Dealer did find a defective rear parking proximity sensor SAM module that was drawing.

I am appaled generally at the poor troubleshooting skills and tools that the dealer has. They should be able to hookup a current draw sensor to main distribution and let me drive it for a week. Had they not found the problem I would have built on myself!

as for time required to change the battery, well it is under the drivers seat. 2 hours is a bit much, maybe 90 minutes is better. An hour for the junior mechanic that does this once a week... this is not rocket science!

The battery is under the passenger seat and there are directions in your car's manuals on how to replace it without removing the seat. I've done it myself several times when I had the same issues. it's not easy, but I'm able to swap out a battery in under 30 minutes.

Dealer removes the seat because it's a tight and uncomfortable removing it how the manual directs to do this and the battery is huge and needs to go in and out at an angle. Space is very limited. If I had more time I probably would remove the seat too.

Recommended brand for battery replacement
 

My dealer advised me that my battery is 'weak' during last maintenance job. They quoted ~$650+tax for replacement ($400 for battery and 2 hours work). I refused, thinking I could do myself.

I thought about Interstate, it is still pretty expensive, I think ~$300 + tax and I could only buy it at some mechanic shop in Canada which wants they commission too.

What battery brand and type would be the best replacement for the stock OEM?

This is what I put in my 2008 r350 last year. http://www.oreillyauto.com/site/c/de...0423&ppt=C0005

I think I'm going with the AGM group 48 battery from Sears for $140.

http://www.sears.com/diehard-advance...1&blockType=G1

Not sure this helps Canadians though. Do you have Sears in Canada?

I also removed the seat, it is very easy to do, just 4 bolts. But you have to be carefull. You can tilt it forward with out disconnecting any wires. If you disconnect, becarefull not to apply power because if you disconnect any of the SRS wires it will flag a code, and you will have to to the dealer to have it cleared. I did this on the drivers side. I thought I had every thing off and yet it still pulled a code.. luckily dealer cleared under warranty