Hello,

I bought recently my E350 2014 , I have popup message in white color that auxiliary battery malfunction and ECO mode in yellow color. As far as I know that auxiliary battery is for ECO start/stop function, is that used for something else and how it safe to keep it for a while.

Another question as I wish to disconnect it to charge it on charger for a while so is it safe to drive the car when I remove the battery until it charged.
The connecters is salty too much what can I use to clean it.

Thanks in advance.

 

The best way to help yourself is by not creating new problems. Keep in mind the steering rack and ESP brakes work with DC power... I would not drive without AUX.

You can easily charge the OEM vented AUX battery inside the car using a CTEK charger set for "small Batts". It vents any flammable hydrogen outside the trunk.

The car itself charges the AUX. battery at every driving cycle.

AUX not being charged normally, may be sign your MY'14 has charging issue with ECU draining batteries while driving.
Keep an eye on MAIN battery voltage, AUX is charged/discharged from it.

 

Thanks for your advice.

Main battery is fine as this issue was before I bought the car and I already drove it for more than 4 days up to 60 miles, but the Aux battery connector looks white from salt maybe need to be cleaned to allow car to charge it.
What do you suggest to clean the connectors.
If didn't work so the battery need to replace as the car was stopped for whole 2022 year until imported to Lebanon.

 

These MB OEM batteries are SEALED AGM with gel acid. No electrolytes should leak out to sulfate the battery posts.

BEFORE CLEANING...
Make sure you're using the right genuine battery and not some random motorcraft replacement. Specifically AUX needs an external venting port.

How to clean... some ppl use baking soda. Auto part stores sell protective spray... cleaning strategies are not my strong suite.

 

I guess it is 3K battery not OEM ( imported like that from USA) but if it will need replace I will get MB OEM one with 120$
Tomorrow morning I will check it and try to clean.Hope it will work.

Thanks again.

 

Here is another option for aux battery.
Some of them have venting hose, so make sure it is connected and venting outside.
Driving without aux battery might trigger whole list of codes. Unless desperate, I would avoid it.

 

Tonight I disconnected the battery and clean the plugs as it was rusted at + sign and salty at - sign, the battery is 3k battery with MB logo and the vent line connected, after cleaning I connect it again but how much driving I need to full charge or do I need a volt meter to check how much voltage during engine running and how much when it is off so what is the range must be.

Thanks in advance.

 

With a voltmeter, you can measure and it should be @12.8V (new), and no lower than 12V. However, that only tells you if it is charged, it does not tell you how much amperage you can quickly draw out, i.e. ColdCrankingAmperage (CCA rating). The car's computer measures the "health of the battery" and if it is below certain threshold, it triggers the message. You may need to take the battery and get it tested with a real battery health tester (Midtronics is the brand approved/that MB uses).

My old one, I charged overnight and it was 12.4V outside of the car, and if I drove it for 30min it will trigger the message. It was tested, and it was 30% health-wise, real CCA/nominal CCA. Replaced it with a new one, and I have not seen the message for a long time.

 

Friday I got new auxiliary batter from MB exclusive dealer in my country with part number "A0009829308" Price 150$ with VAT, I replaced it in my garage and the message didn't popup again!!!

I check the HOLD feature it is working fine but still ECO is yellow but I did short trip for 5 miles not more maybe I need to move for more mileage to satisfy all parameters.
Can I use HOLD and Start/Stop at the same time or not for example at traffic light stop can I use HOLD feature instead of ECO start/start without disabling ECO from dash panel.

 

The ECO stops have mind on its own.
I have/had 3 cars with the feature and only 1 was very predictable how it works. My present W212, driven few days apart need about 10 miles before ECO will start working. I wonder if that is the battery (2 yo) needing charge, or AC in 90F weather.
On my GLE, when I bought it, ECO would not work at all for a year, till I replaced battery. Now it works, but only for 30 seconds, when our red lights have a minute long schedule.

 

Today I tested it the ECO still yellow, for something no idea why after parking at market to get something then move the ECO turned green for 1 mile after I got greater than 30 mph it turned yellow again but at least I got it enabled so battery replacement fix whole issue.

 

What scanner do you have? There are several parameters that need to be meet for ECO to engage. Guessing or judging from coffee grinds has low success rate.

 

I didn't use XENTRY, it was I guess Autel MaxiSys. But now no errors on dashboard and hold feature is working as it is so for me ECO not required as most of my trip is short trip with total 100~150 miles a week or 2 week. I will test it when I go highway and then move to a city at traffic lights ( away from my home around 20 miles) in the coming weeks.

 

The $100 scanners today will open ECO troubleshooting page.
Easy, peasy.

 

Amazing ECO glowing green then deciding to glow Orange all on it's own without any engine stop is only the proverbial "tip of the iceberg".

The underlaying causes are poor alternator management by the engine control module.

A normally working W212 turns on "ECO" available flag under 10mn and keeps operating stops after stops under 3mn max.

Instead of trying to fix a busted ECO system, enjoy that you don't need to disable it.
✌️

 

As I said before I am not looking too much for this as my inly concern that my battery which I replace it and hold feature available now so for ECO I will not make anything if it work later after some long trips so I will disable it in that trips(from dash board) if it doesn't work so it is not big deal.

 

it's a little more complicated... long trips can make ECO worse instead of better due to car screwing glitching the ECU voltage management.

To simplify what's what:
AUX ---> HOLD
MAIN ---> ECO

AUX + MAIN get charged together by the amazing alternator through one-way curcuits.
When MAIN gets abused, so does AUX.
✌️

 

To back up your theory , let me tell you about my other car (non Mercedes-Benz product) in regards to ECO .
Sometimes, it automatically turns ECO off on its own even without my interference (without pressing that rectangular button to turn it off ) .I must admit it saves me from hassling thru that process
Sometimes, I see a notification the gauge cluster saying " energy saving mode activated" I don't know what it means
Sometimes, it automatically switch on the ECO mode even after turning it off by itself

 

All the cars I have/had with ECO option are MB.
My diesels don't display ECO in different color, when it is activated. When the dash light is always the same, ECO sometimes work, sometimes not.
We are driving 5 miles to the freeway, with lot of lights, who can stay for couple of minutes. Not having ECO working in such time gets annoying.
I even made a battery cable with plug in front grille, to keep the battery fully charged in days when we don't drive. That helps, but not always.
I drive with monitoring scanners, but they don't show ECO features. The one that does is laptop based, so not easy to carry on the road.

 

I see it was unpredictable, yesterday night, I start from cold and made a trip for 2 miles ECO light still yellow while today I made a trip for 1/4 mile stopped for 10 minute then start again for another 1/4 mile to move around and return back to street I noticed that when I stopped at right side to check the street empty to turn around the engine stopped over brake and ECO light green then moving foot from brake the engine start again,after turn over and move the ECO light turns yellow until home. Engine temperature was around 80C and air temperature around 79F, windows opened from my side nothing else. I am guessing that the ECO light turn green if you did two consecutive stops during the same trip maybe as last Sunday did the same as after stopping for couple of minutes(engine off) at the shop and move again ECO light turn green.

 

What I noticed is that ECO will not work right away when you brake from higher speeds. Probably due to high exhaust temperature.
On the E (now sold) who was more predictable, I would come to stop on freeway exit red light, wait 10 seconds and move 2 inches, when ECO would kick in. The ECO when works will engage for several stops & goes we do during heavy traffic at red lights.
Than when battery gets low, the engine will restart , when you hold the brake. Scared me pretty hard the 1st time.

 

I'll keep it for time to understand how it works and get a look to the book manual to check it too. Since my ebook at command is stuck at choose language and not opening.

 

An update:
Today I had a trip for 100 miles(Both directions), when start at cold and during the first 14 miles the ECO light was yellow until I achieve the gas station when I stopped the engine after filling the tanks and start the Engine and moved, the ECO light turn green the whole trip. Afternoon when getting back to home after 2 to 4 miles the ECO light turn green and keep until get home. So I guess it is working as expected maybe it need sometime to enable the first time in the same day specially moving above some miles.

 

That sounds about right for your ECO to get ready and stay ready regardless of extended driving trips.

I would guess your charging voltage management is likely still functional at this point.

Try to keep main battery on a CTEK FLOAT charger during extended parking periods of more than 3-5 days.

Enjoy,

 

I'm getting the "Auxiliary Battery Malfunction" since Saturday. Stop "Hold" function is disabled.

I've recharged main battery to "floating" -- it recharges Aux. Battery, too, yes? -- then used the IcarSoft 3.0 to run codes. Got a CGW[ZGW] Central Gateway fault. I reset this code successfully, and the Malfunction Message goes away and Stop "Hold" resumes working. Unfortunately, the message returns after one drive cycle. (One drive was 4 miles, and the last drive cycle was 24 miles in length.)

I haven't tried charging the Aux. Battery separately. I assume to do this that I remove the battery, but I am reluctant to do this, for some reason...

So, should I go ahead and buy a replacement Aux Battery and hope that solves it?

FCPEuro price ($160) is $10 higher than the MB Dealer, LOL.

I'm tempted to try Krzysztof's suggested Amazon Battery noted in Post #6 above.

Any suggestions?