Hey guys, I have a weird one here:

I had the original, 9 year old, battery in my 04 E320 finally crap out on me recently. I drive the car very rarely and typically leave it on a tender/ charger, so after I drove it for a few days and noticed that the battery was getting weak, I figured it was time to replace it. I went to a local auto parts store (within walking distance of my house) and picked up a replacement Bosch batter of correct group type. The car started and performed fine, drove as always, although I did notice that the automatic "up" feature on the windows did not work, nor did the rear power hatch (it's an estate wagon). Nav worked fine, as did Sirius and the cigarette lighter.

The new battery was installed on Friday afternoon. That evening the car was taken to dinner, shops, and then returned home. All in all around 30 or so miles with approximate 4 "starts" of the engine throughout the trip. Saturday morning the car was driven approximate 60 or so miles down to the shore, parked for 3 hours, restarted, driven, restarted and then left over night. Sunday morning, same thing, I did some shopping, 3 or 4 starts leaving the shore early afternoon for the 60 or so mile return trip. Once I got home, I left the car in the driveway.

Throughout the weekend at no point did I notice anything peculiar or abnormal with the performance or starting attributes of the car. The only thing of note was the windows and the rear hatch.

Monday morning I went out to start the car and it was completely and utterly dead. I hit the unlock button on the key and noticed immediately the dash had the red screened warning "Battery insufficient for braking" or something to that effect. It was a warning I had seen previously when the battery "faded to death" or rather when the car would still try to crank, but the voltage was insufficient. This time there was no crank, no click, I simply turned the key and the Nav screen went black.

I thought this was odd, so I pulled the new battery and tried a load tester. The initial reading was 10 volts and after putting a load on the battery it dropped to a mere 4 volts, indicating that the battery was, in fact, bad.

I also noted that the manufacture date on the battery was July, and this being Mid-Late October, more than 90 days, that could be a serious issue.

I turn to you, the Benz experts, and ask: Does this sound like a bad/lame battery, or something more? I'm trying to determine if a faulty Battery Control Unit may be to blame, but I'm unable to find a list of symptoms related to that issue.

Any and all help is always appreciated!

Cheers!

-Sean

 

could be your second battery. but i think you have bad alternator.

 

I tested the voltage to the battery this morning, with the car running and it read a fairly steady 13.85-14.10 volts, so my thinking is that the alternator is charging. I did, however, also notice something else not quite correct. I went to adjust the clock and could only change the time in 30 minute increments. All of these issues were not present prior to changing the battery

 

Sorry! I apologize, I should have clarified that I returned the previously bought battery and replaced it with a new one.

The battery that is in the car at this moment is brand new, picked up and installed last evening.

So far the car is starting and performing fine. I still have an issue with the electric tailgate, but I was able to reset the windows and sunroof so the automatic open and close works fine. The clock also appears to be set to the right time, although I can only change the minutes in 30-minute increments stilll.

Sorry for the confusion

 

So if I read this correct - your orig 9yr battery died. You replaced it, but the 2nd battery failed or was a dud after a short time. You replaced that and all OK again?? (except the tail gate)

So fixed. And problem was just a crap 2nd battery causing the head-scratching.

 

If it happens again I am sure a module is active. Since the tailgate is not operating correctly I would look there first only if the battery dies again. If you have a volt meter you can pull some fuses to find the culprit. I had this issue with a sprinter overhead control panel before. It was caught in a loop is the easiest way I can explain it.

 

The big battery in back is just a car battery. The little battery up front is a fail safe device for the EBC.

If the electronic brakes (EBC) warn of a fault, that is the little battery up front. So that you have brakes if a battery dies, there is a second battery for backup. If the car detects something wrong with that little battery, it warns you that your brakes might not work.

 

I had an intermittent battery drain for at least a year. I put an amp meter on the battery (clamp type) and pulled every fuse that I could find. I one point I thought it was the cell phone battery in the center console.

I took it to the dealer and they replaced a CAN Bus part in the truck and said they fixed it. I had the same problem and car died over night. I brought it back and they finally fixed it.

As it turned out it was the teleaid module in the truck, it was defective. Even thought it is not used anymore (analog version) they could not just unplug it as it is part of the SRS system. After several days they got help from MB and were able to disable it with out it affecting the SRS system.

The reason pulling the fuses did not find it is there are no fuses for the SRS system which teleaid is a part of.

Not sure if this is your problem but thought I would put it out there.