nopcbs

Car: 2006 E320 CDI with 31,000 miles
Main Battery: Deka AGM Exact Fit EAS9AGM49 purchased from AutoBarn.COM ($195) in November 2011; installed spring 2012 (car stored on battery maintainer all winter)
Auxiliary battery: original battery that came with car

Problem: the original battery (which came with the car) was replaced because in Fall 2011 it began to give the "weak battery/convenience features disabled" message which would then go out after a few minutes of driving. At its age, I was not surprised, so I bought a new Deka AGM battery from AutoBarn.COM. and installed it in Spring 2012. (Car was stored all winter.)

Well, this fall the same thing started happening, again. After standing all night, I get the weak battery/convenience features disabled message regularly. I took to car to Grand Blanc Motors (M-B dealer) for another problem and when the car reached them (60 highway miles from my home) and it was being checked in, it gave the weak battery message...on a cool, but not cold Fall day. The service manager mentioned this to me and I told him about the 1 year old main battery and that I thought that this was due to the old auxiliary battery still in the car. He said that a failure with the aux. battery gets you a different error message. So I asked him to check the charging system and load test the battery. The charging system was OK, but the battery load test gave a "charge battery and re-test" result, which is indicative of a failing battery. It passed after the re-charge. I got the car back and for a few days the weak battery message did not show up, but now it has gotten cooler (mid-20's at night) and Iget it regularly on a first start of the day and sometimes even when the car has been run long enough to extinguish the "convenience features disabled" message, then been turned off as I shopped for ~30 minutes and started back up. It takes about 5-10 minutes run time to get the message to extinguish.

The car always start w/o issue, although it seems to turn over a little slower than in summer, but not much.

I imagine that I just have a bad battery, but it puzzles me that the message comes up even when the engine is still warm. Seems to me that a battery that weak would be near dead standing over-night in mid-20's temperatures and take a lot longer than 5-10 minutes running time to charge back up.

Anyone have some thoughts?

- nopcbs

mtrevelino

Your small aux battery is coming up on seven years old. My thoughts are to change this out. I believe that this will solve your problem. You should be able to find a battery for under $60. Make sure that it is fully charged before you install it.
Mike T.

nopcbs

That's what I thought, at first, too. And that's what I mentioned to the service manager.

He poured cold water on the idea because he said there is a separate error mssage when it goes bad. Besides, the aux. battery is ONLY used for emergency backup for the brake system and nothing else. So a bad aux. batt would have zero effect on the "convenience" systems like the bun warmers. It does make sense. On the other hand, I already have a replacement battery on the shelf (dry pack/electrolyte not added) and it is ~7 years old, so it would be an interesting experiment. Or, just for grins, I could put the main battery on a maintainer over a cold night and see if that prevents the error message. If it does, the problem is with the main battery as the aux. battery is not on the same circuit.

These are German-designed cars, so anything is possable, of course.

- nopcbs

vettdvr

Replace the aux bat X 2

nopcbs

This is from personal experience or a hunch?

I'm game to do it (easy), but, like I said, just for grins, I think I'll try the mainainer on the main battery overnight, once, first.

Hate to put the new aux. battery in use unless I am sure it needs it.

By the way, my dad has an old Ford Explorer, bought new, that he just replaced the battery in, for the first time after 10 years! He did not really need to do it (it was working fine), but his grand-daughter refused to go on a long trip up to the Michigan UP from Chicago in it unless he did. He gave in. Friend at work has a 12 year old battery in his Chevy Cavalier...in mid-Michigan. Sometimes even the cheap oem ones really last a long time.


- nopcbs

Gadget

Will installing a new aux battery throw off the fuel level gauge for a while?

I replaced mine Friday morning then ran my car out of gas with 1/4 tank showing. Never did that before.

G

nopcbs

All that stuff should run off the main battery. You can lose settings if you replace the main battery w/o putting another battery in parallel as you do it.

- nopcbs

ozusa

Check out the voltage of the aux battery and probably replace it regardless.....

My reasons for saying check the aux are as follows:
1) It is OLD. It will let you down before long, even if it is not the cause of the current* issue
2) You may have two (or more) issues, perhaps involving the aux, so don't spend all your time and detective work in the trunk
3) Personal experience. I had a battery message that did not specify the aux battery and it disabled functions as yours has, but replacing the very old aux fixed the issue easily
4) This is the wrong time of year (Nth Hemisphere) for batteries to fail. I do not mean it is an inconvenient time to be stranded in the cold. I mean batteries die of old age due to heat in Summer far more often than they fail due to cold in Winter. I think a one-year old battery (your main) is less likely to be bad and failing at this time of year than an old Aux one
5) If it is your main battery that's the problem, you are especially vulnerable to needing the aux battery for brake backup. Now more than ever, you need a reliable aux battery, so get one

I realise the above statements are not perfectly logical, but it is more than a hunch.

* pardon the pun

starbrite

What kind of battery mainter is the op using? Keep in mind that, like the original, the Deka
AGM requires a different charge scenario than a standard battery. The Ctek's seem to do the best job of correctly charging AGM's.

BTW, my '04 still has the original aux battery w/no problems.

nopcbs

Two nights ago it was in low 20's and the next day when I started the car I got a big red background on my central dash display with a picture of a battery and a "go to workshop" message. Car started and ran and a little later the red went away and I got the usual convenvience features disabled message for a few minutes and then that went away. Next night I left car on a battery tender all night. When I started it next day, no messages at all, even though it was in mid-20's. Then, later, at work, I got the red circle thing again followed by the convenience features disabled message. That experiment convinced me that the main battery was defective (I had not charged the aux. battery) and my problem had nothing to do with the 6 year old aux. battery, just as the M-B service manager had said. I contacted Dekka (it's a Dekka battery) who sent me to a local distributor who gave me a list of local dealers who they can deliver a replacement battery to (24 month replacement guarantee and I am at 13 months). They said the local shop would have to comfirm the battery was bad. Took the car there, they load tested it and confirmed that battery was bad and my charging system was good. New battery comes tomorrow.

So, this had nothing to do with the 6 year old aux. battery. As I said, the M-B dealer was right when he found the main battery was weak.

Interesting sidelight...I posted same message as here, asking advice, on another M-B forum. Some guy there calling himself "ForcedInduction" answered that main battery is ONLY used to atart car and aux. battery supplies all accessories. So, I should replace the aux. This is, of course, utterly wrong and I gave the guy a M-B training pdf link that explained how the two batteries work and that the aux. is an emergency-only battery and used to supply power to the electro-mechanical braking system in W211 series cars in case of electrical system failure so that braking still works. I was polite, but did ask him where he had gotten this peculiar and very wrong idea. ForcedInduction blew up at this and had me bounced off the forum and used profanity in doing so. I got a message from the forum master (who may actually be ForcedInduction) confirming I was bounced off. I protested that I was right and FI was wrong. He told me to prove my point. I did, even including a scan of the car's manual page that discusses this stuff. Plus I found/sent a nice auto supply trade group web site link that discussed, in some depth, troubleshooting of the SBC braking system that M-B introduced in the, then new, W211, in 2002/2003 (EU/US). The forum master jumped on this claiming lack of accuracy in the piece because, he said, the W211 came out in 2007. (Duh?) At that point it became obvious that neither guy (if there really were two of them and not just one) knew what the heck he was talking about and our exchange ended with him perplexed that I did not just take it lying down and me perplexed that these two (or one) were posting stuff in/managing a M-B forum as if they had a clue and clearly lacked even one and could not recognize one when presented to them.

My point? Be careful in accepting what you read out in some of the M-B forums. There are clueless people posting nonsense and, worse, there are forum masters that are just as clueless and support them even in the face of contrary documentation...and rational thought. (Mr. FI was not asked to document anything, by the way.)

Not this forum, though, thank goodness.

Real eye-opener here.

- nopcbs

Gadget

The forums are all about sharing information and helping each other out.

Sometimes even people with the best intentions are wrong. It happens.

It is a damn shame when you had good info based on documentation that you attempted to share with the forum you were attacked over it.

Based on what you just posted I will be replacing my main battery. Thanks for sharing.

Would you happen to have the referenced document you can link to or maybe email me a copy of it?

Thanks!!

G

nopcbs

http://www.moderntiredealer.com/chan...x?prestitial=1

and

http://www.mercedestechstore.com/pdf...2011-29-02.pdf

You can look in your manual. It's page 450 of the 2006 E320 owners manual that talks about it, though not in depth.

The two links are very good.

- nopcbs

Gadget

Awesome.

Thanks!!

G

nopcbs

I think that many if not most W211 owners know that the cigar lighter comes, from the factory, set up so that it is "dead" unless the car is turned on with the ignition key, but that one can easilly change that so that the cigar lighter is "live" at all times by moving a jumper (fuse as I recall) in a fuse box that is under the hood just in front of the driver (US cars). I did this and it makes it VERY convenient to then put your car on a low current maintainer/charger such as a Battery Tender. You just have to make up a cigar lighter adapter that plugs into your Battery Tender or similar device cable. Costs about $2 to do it.

I was using such an arrangement to store my car over winters and keep the battery fully charged, but it works great for topping off a battery in very cold weather, too. No rooting around in the trunk. The cigar lighter port can be used to charge the main battery, but not the aux. battery...that one you get at under the hood.

Instructions for which jumper to move can be found in this forum. That's what I did.

nopcbs

I received a new Dekka battery to replace the faulty one (24 month replacement warranty). I took the "bad" battery out myself and replaced it in the car with the original Varta battery that it came with. The Varta had been pulled early in 2012 and had sat on a bench in my garage ever since. It's failure symptom was the "convenience features disabled" message in Fall of 2011.

I put my charger on the Varta before putting it back in the car and the charger immediately went into trikle charge mode. In other words, it still was holding a good charge.

Well, that old Varta (about 7 years old) has been in the car through the weekend now and it is performing like a champ. No "convenience features disabled" messages and it starts the car just fine. This leaves me with a brand new $220 Dekka AGM battery sitting on a bench in the garage and me with no real reason to put it in the car.

And that 7 year aux. battery continues to soldier on w/o difficulty.

Varta makes pretty darn good AGM batteries.

- nopcbs