Well you're in the wrong forum. It could also be the alternator/voltage regulator. Not sure if you have a battery control module as you're in the wrong forum, early W211s had it, later ones didn't.

 

The Die Hard Gold main battery in my daughter's 2004 E500 crapped out and the infamous red battery icon was lit. I gave this car to her 5 years ago, and I was the original owner. So Dad being a nice old guy, pulled the battery today and went down to Costco and picked up a new Interstate AGM and installed it. The old battery was installed in 2013 and had a 3 year warranty. Not bad. So... the car started right up but the red light still appears after startup, goes away after any button push. So I'm wondering if the auxiliary batter under the hood is needing replacement. I know I replaced it before I gave her the car, just don't have that receipt. Poking thru this thread I see Post #522 and he suggests using the generic reference of:

14-BS Battery replacment (12V 14Ah Sealed) Maintenance Free Battery.

That should translate into a: 14-BS 12v 14 Ah AGM sealed battery correct? Finding one seems a bit more difficult than I thought... you google that and similar batteries pop up but they all seem to be 12Ah rated. However, I went to BatterySharks web site and found a Sigma-Tek motorcycle battery Model YTX14AHL-BS. Its 12v, has 14 Ah rating, 210 CCA measures 5.28" long by 3.54" wide, and 6.54" tall, weighs 10.42 pounds. Haven't removed the cover yet so I can't compare the size. I remember the battery is motorcycle sized, I just don't know if its 100% compatible. Also I'm wondering if there's simply a need to clear the computer with a sequence of button pushes? Anyone have a clue?

 

Person with a clue here. I have a 2004 E500 4Matic that we bought new and I still just adore. So I have been exactly where you are. I now know as much about the electrical system as many mechanics, so feel free to ask follow-up questions. I also posted a how-to somewhere on here regarding changing that AUX battery (easy, but be careful and methodical).

The AUX battery is your issue, I think. See below about that. 14-BS is just a size. Don't worry about AH. BS means "bottle supplied"; i.e. one that comes with the acid separately, because those are easier to ship. But the size is 14. Give me 5 minutes and I will have suggestions for you. I have a Die-Hard 14-BS Motorsports battery now in the car from Sears that I bought a while back, and a YUASA YTX-14BS before that. Both work great. Hang on and I will post a bunch of links. You DO NOT want a 14HL. Wrong size. You want a plain old 14.

DieHard from Advance Auto Parts: https://shop.advanceautoparts.com/p/...000%7CL3*15597 (Advance used to have an AUX14 battery that they sold specifically for Mercedes, and this is it in a new package.)

Advance also has what I'm confident is what I have in the car (having purchased it from Sears Auto Centers several years ago): https://shop.advanceautoparts.com/p/...archTerm=14-bs Their online indicator will say it doesn't fit your car, but that's just because ALL of the indicators will say it's for Motorcycles, because it is. This is a 14-BS AGM battery that you put the acid in yourself, and it will fit perfectly. I know because I have it.

YUASA YTX-14BS, which I had for years in the car, perhaps the best brand of powersports battery made [if authentic] through Amazon (but sadly not FROM Amazon anymore; they had a better price and you would know it's authentic):

VARTA (the OEM battery) from Pelican Parts: https://www.pelicanparts.com/More_In...=3868&DID=5038

Everstart from Walmart (if they have it locally): https://www.walmart.com/ip/EverStart...-14BS/16795217

Finally, since you're a Costco member and if you like Interstate, this one should work, I think. You might check the dimensions and which side the terminals are on compared to the YUASA [which I now did and, at least using the specs on the web site it looks fine], but I think this is just a TX-14 battery (no "BS" because they install the acid at the factory, like the AUX14 from Advance). https://www.costco.com/interstate-ba...100655022.html

You can usually work out a speedperks discount from Advance, although they have been resistant with the Die Hards. If you ask at the store and say you'd rather buy from them instead of ordering a YUASA from Amazon for $50 less, you'd be surprised at how cooperative and helpful they usually are.

NOTE: You want the 14-BS size, NOT the 14H-BS size. They're different.

These are decent prices on the major, reliable brands of batteries. Any 14-BS size should work, but you went out and bought your daughter a really good Interstate battery, so I know you want quality for her.

One tip: Advance will do a free battery check with the exact device that Mercedes says you have to use on an AGM battery to get a proper evaluation of whether it works (Midtronics tester). Advance actually told me my main battery was fine once when the light came on, and then I replaced the AUX battery and voila! -- light went off.

Another tip: The AUX battery only gets ten minutes of charge per start of the car, which was why my light would go off briefly when I did a bunch of driving stop and start around town, but then wouldn't go off after I drove one hour-long trip. So, because it doesn't get much charge from the car, be sure you fully-charge it at home before installing it (assuming you have a charger that has a nice low 2 amp or whatever charge to give the thing). Don't take any store's word that it's "fully charged" when they give it to you. It never is. Ask them to top it up and you'll come back later or tomorrow (but pay for it now).) If the main battery in there was as old as you think it was, then you got great life out of it and it would need replacing soon, but it probably didn't need replacing quite just yet. It's hard to believe that my car is 17 years old now, with 209,000 miles on it, because it still looks fantastic and runs great, but I got about 9 years out of my Die Hard Gold main battery, as much as the couple of times I had to go to the dealer they commented on how it wasn't the OEM battery. Yep. It isn't. And that's just fine with me.

AS TO THE BUTTON PUSH: I'm not really sure why the light goes out after you push a button after start. If I had to guess, because I had a similar thing where it would come on or off, is that it goes out shortly after starting because in the first 10 minutes of running, the Auxiliary battery is getting a charge from the alternator. After 10 minutes, it stops charging the aux battery (but not the main one, of course). And the cycle of the light coming on and then going off repeats. Before replacing it, if you want to try putting it on a charger (after disconnecting the leads) and seeing how that does, you could certainly try that before spending $70-120 on a new one. Or drive it over to Advance if you have one locally and have them test it. In my experience, they have the Midtronics tester and they're very honest about it and give you the printout if it has one, and/or do the test in front of you. At least where I am, they seem very-much dedicated to gaining customers for the long-haul, and telling someone they don't need a new battery is a good way to ensure that you'll come back to them when you actually do. Of course, it might be different where you are.

One final thought: Sometimes that red battery light means that the alternator isn't working. A quick-and-dirty way to test that is this: Go into the secret menu. To do this, insert ignition key, turn to the first detent (i.e. not the two clicks to fully on). If the temperature isn't showing in the main display, push the arrow buttons on the steering column until you're looking at the temperature. With the temp in the main display, push the odometer reset button (the thing that adjusts the brightness of the dashboard display) three times rapidly until the thing beeps. It will say UB: 12.1V (or whatever the voltage is). That's the voltage at the battery. Now start the car by turning the key the rest of the way to the right (don't turn it back first or you will have to restart this process). It will usually then show a voltage somewhere around 14 with the engine running and the alternator operating, but the exact number isn't important for our purposes. What's important is what happens if you rev the engine or start driving the car (you may have to clear the battery light by pushing the arrows again until the display comes back around to the UB: XX.XV display so you can watch the voltage). If it DROPS significantly when the engine is running or revving, then it may be an alternator issue; the engine is running off the battery rather than the electrical system, or, put another way, the alternator isn't putting out enough juice to run the car and it's drawing off the main battery. If your daughter was able to drive the car around with the light on previously and didn't get stuck somewhere, then this is probably not the issue, but it's an easy quick-and-dirty test.

 

Hey guys I've been searching all threads about red battery warning lights here for weeks and see a lot of different cases with different causes leading to the same issue. And since the charging system comes with so many controllers, that's what got me lost. Sometimes it seems to me that I knew what the problem was since I had done some diagnostics on the system, but when I intend to replace what I think is the cause of the problem, I hesitate and get confused for fear of replacing the wrong part . Pardon the length of the introduction. In general, before discovering this issue, I had done something on the same day that may have been a mistake and the cause of the problem, and it may not be, but before I say what I did to it, I will tell you about the state of the charging system before, in order to avoid the possibilities of wrong diagnosis. Exactly a year ago I had a battery drain issue, so I assumed the batteries were bad, since they were around 5 years old,so I put new batteries from mercedes dealer but it didn't solve the issue, next I replaced the voltage regulator but did not solve it aither. after that I had to go harder with the diagnosis, at the end it was the front passenger seat control module, replaced it, and everything becomes fine, After that I didn't drive it for six months as I went to another state for work and now I'm back. Of course the battery was disconnected, and here I will mention the thing I did that made me suspect that it could be the cause of the problem, and without it I would have suspected on the alternator only. since I don't know how old it is. Ok what happened is my trunk can only open when the system is powered, so It can not be open with the key blade due to bad trunk lock, so I had to connect my battery charger at 2 amps settings to the alternator. the red clamp to the B+ terminal connector at the back of the alternator and the black clamp to a ground point. I got the trunk opened and recharged the batteries and Guess what?!! I forgot to reconnect the auxiliary battery terminals and started the car. A few minute later, All Electrical consumers started to turn off one after another. I remembered that I forgot to reconnect the auxiliary battery so I reconnect it back and started the vehicle again، But nothing changed for the better, and after about ten minutes the red battery sign appears. That's when I realized that the car running off the battery not the alternator, so I checked the voltage on the alternator with the car on and off and it was the same voltage as of the battery, so the alternator doesn't produce any power, because the voltage doesn't increase when I start the car. now the question is, Is there a possibility that what i did caused the system to short out? I'm suspecting a shortage either on the auxiliary battery relay or the ×4/10 fuse. i know I've said a lot but hey it is a nightmare I am sure that everyone who has suffered from this problem feels me, and I hope everyone who has experience and can help does not skimp on me. any help will be appreciated, thanks

 

Hi,
I'm driving a 2004 E320 4Matic wagon, which is regularly serviced at excellent dealerships. In 20 years owning the car, I have not ever seen the "Visit Workshop!" red message, paired with a battery symbol, until today.

The car started up just fine, which seems to indicate no issue with the main battery. Today is Saturday; it was last driven on Thursday, no problems then. During the few minutes that it was on today, the engine was smooth; it did not sputter. (Given the error message I turned it off and scheduled service for Monday.)

The auxiliary battery was replaced in January, 2022 (I will ask the dealership on Monday to check the aux battery's relay.) The main battery was replaced January, 2020. The alternator was replaced in late 2019.

Just wondering if anyone thinks the earthquake yesterday - around 100 miles from where I am - might have caused an issue with the wiring? When the earthquake occurred, I certainly felt it. But nothing fell down (like paintings on the walls.) Only a door on an antique cabinet popped open.

It was suggested to me by a family member that maybe the earthquake shook something loose related to voltage, on the car. Just curious what those on this forum will reply about the "earthquake theory."

I came to this forum to try to figure out whether it would be safe to drive the car over to the dealership for service (located within 10 miles.) Apparently, assuming it starts again on Monday, I won't need to have it towed. Thank you for the background knowledge gained from skimming through the postings on this forum.

 

I doubt it. The car gets more shocks just from driving on bumpy roads than it would have gotten from an earthquake. It's not like a building which isn't designed to move, but it has shocks and springs to cushion movement and the whole car is designed to take sudden movements. You also have a battery control module so that could also be going even though you have a new battery, aux battery and alternator. You could also check the voltage of the battery and see if you're getting around 14 volts while driving and around 12 when it's off. I think it should still work on the pre-facelift, switch to the temperature display and hit the reset button 3 times with car in the on position without the engine running. Should get the voltage display.

 

It should be higher than 12v when switched off (more around 12.6)

 

That's a standard state of charge chart that refers to a battery at rest with no load at 70 degrees. The voltage display is not a battery at rest and there's a load on it so you will get a lower voltage. Typically I see anywhere from 11.8-12 volts in colder weather. I killed my battery once and threw it on a charger and afterwards it was about 12.5, but once it was on the car, the dash voltage dropped to something like 12.2 or something like that.

 

Your chassis drains batteries besides them and alternator being recently replaced by dealer.

I am going to guess you have a battery drain while parked. Simply use a CTEK battery tander to workaround this issue.

Furthermore someone should scan your chassis to list was sick modules are "not sleeping" in low power mode. Replacing bad parts is the last step of a good repair once the issue are identified.

Water egress usually damages simple electricals connections os SAM Module in charge of the whole chassis power Mgt.

If you're not comfortable driving a questionable car ask dealer to arange for towing. Low voltage is best not to be trusted with your life.

 

? Never heard this one. I've changed like three aux batteries without disconnecting the main battery. Probably a good idea though. BTW if you don't change this aux battery, it will leave you stranded. Don't as me how I know.