G10Eclass

I had my main battery changed a year ago.
Normally after starting my car and driving off, within 5 seconds the ECO sign on the display would turn from yellow to green every single time without fail.

From yesterday, it just doesn’t go green at all.

Im thinking it could be the aux battery.

Any other suggestions?

PeterUbers

https://mbworld.org/forums/c-class-w...p-feature.html

terryttk

I had the same issue with my 2014 E63S. Both batteries were new but after a few months the green ECO light turned on less and less. I also noticed the starter wasn't spinning as fast over time. This was with daily driving and then was even more pronounced when I switched to only driving the car on weekends (50-100 miles). Some posts on MBWorld suggest that Mercedes alternators don't fully charge a battery, and of course modern cars draw current even when fully shut down. Not sure if either of those was the root cause. Regardless, I invested in a CTEK battery charger and now all is good. Starts are always super crisp and the green ECO light comes on within about one minute and then is pretty much always on after that.

I went with CTEK because that's the OEM on the Mercedes factory charger (p/n 000-982-29-21), which is of course way over-priced. The 2014 E class glove box manual says to never charge at higher than 14.8v so to be super safe I went with the CTEK US 0.8 ($70 on Amazon) which charges at 14.4v max. It's mostly meant for smaller batteries but does "maintenance" charging for car batteries up to 100ah (my front starter battery is 80ah). I also thought it would be good for the smaller aux battery in the trunk if I ever needed to charge that.

The Mercedes manual says to always charge using the jump start points in the engine compartment so that's what I do. With the charger on the floor, if I angle the positive (red) charger clamp 45 degrees and route the wires around tall engine components, I can put the hood in the almost closed position, resting on the latches, which I understand is much better for the hood struts than leaving the hood open. I don't close the hood fully. My car generally reaches the fully charged state in about 14 hours. I leave it hooked up after that for trickle charging.

I also bought the CTEK Comfort Indicator w/ Clamps ($19 on Amazon) to monitor both the starter and aux batteries when I'm not charging. You just clamp it on and it reads red, yellow, or green. I've checked the aux battery in the trunk multiple times over the six months since I bought the charger. It always shows green so I've never tried to charge it. Maybe charging the main battery through the jump start points keeps that one charged too? Not sure.

Anyway, I'm really happy now to always have a fully charged battery when I set out. Like some others on the forum I'm still undecided as to whether using the ECO start/stop is a good idea in general (fuel economy vs. starter wear). I always turn it off after a cold start to let the engine warm up. Then once warm I usually end up putting my car in S+ anyway and jamming down the throttle!

Hope that helps.

suicidedoors

I bought my car from a buddy and had no idea it even had ECO mode - or at least that the car started up in that mode - until I replaced the aux battery in the back. So I'd start with that because it's relatively cheap and easy.

terryttk

When my aux battery started to go the car put a warning message on my cluster every time I started it...

JimmyR

It won’t be the auxiliary battery as you should get an error message in the dash - something like Aux Battery malfunction - when it has given up.
But I would check that the connections to the auxiliary battery are tight. I had to replace the main battery recently and then my Eco function started acting up ie the ECO light going green to yellow or the symbol disappearing completely. Turns out one of the connections to the auxiliary battery was loose, presumably as not secured properly after testing it.

mbwillgrubs

Quick copy and past from 2013 CL 63 owner's manual:

The engine is only switched off if:
Rthe outside temperature is within the range
which is suitable for the system.
Rthe engine is at normal operating
temperature.
Rthe set temperature for the vehicle interior
has been reached.
Rthe battery is sufficiently charged.
Rthe system detects that the windshield is
not fogged up when the air-conditioning
system is switched on.
Rthe hood is closed.