Jose3147

i need help. My main battery signal (red) on dash board came on yesterday.
I barely made it home. I purchase a new battery of the same specs from autozone to replace it. My car turns on but the red warning sign does not go away.

Is my alternator bad or
Do i need to reset the ecu. How do I do that.

I also don't know if I need to replace the aux battery I'm not sure where is it. Or if I need radio codes I need instructions. Need help.
Would like to do it myself and avoid going to a shop.

Thanks.

DanD.

Here are the videos I have saved fir myself, Im planning to do this job in a few months.

Main

Aux

Please let us know how hard was it.

Jose3147

I have a newer model and I can't find the aux battery. I had seen same vid and did as is. But since I can't find my aux battery to check it. I don't know we're my issue is at . Thanks for the info

DanD.

Watch the first video and at the 9.09min when the guy pulled the main one out you will see the aux on the right side.

Jose3147

Mines is on the back. I just found it. Right side below the spare tire. But the voltage is 12.7v so my Aux Batt is ok.

DanD.

How hard was to replace the main one?
Can you post MB part numbers for Main and Aux?

Jose3147

The main is easy. Just like the Vid you posted. For the main You need a H8 AGM battery. You can get it at any auto parts.

DanD.

Im considering to use Duracell as the Main
https://www.batteriesplus.com/batter...iesel/sli49agm

How long did it take you?

Jose3147

It's a good option. 30 min job

k9lovr

Thanks for posting this up...more DIY's are needed in this forum....appreciate the insight and info guys!

Mercapotamus

Fyi - I got the same battery from Sam's Club for $170 last month. Works fine so far.

DanD.

This is very good to know. Thank you.

Jose3147

An you share with us the brand and model # that you got in Sams

Mercapotamus

The details of the battery are in the link that @DanD referred to in his post.

Here's a screen capture of the details of the battery from Samsclub.com:

Jose3147

Great. Good info for the ones looking to do it. Thank you.

burnout

What' the warranty on the duracell?

DanD.

Type: Standard
48 Month Free Replacement Warranty
2x more cycle life than conventional batteries
20X more vibration resistant than conventional batteries
100% spill-proof and maintenance free AGM technology
2014 Mercedes Benz ML350 V6 3.0L 850CCA Diesel Car and Truck platinum AGM battery

kenmakara

Why is that battery so much smaller than the auxiliary battery that the car came with? This diagram shows our cars have the main battery (1), auxiliary (2), and a back up (3) battery. That small one in your pic looks to be the back up battery. I have a W166 and trying to replace my auxiliary battery replaced, but I'm a little confused. (3)

jdward

That is a darn good question. Why is that auxiliary battery so small or why is the bracket so big? That looks like what must be the hold down bracket on the left side of the photo. In the 2013 ML350, is there an auxiliary battery located in the back, right side, behind the panel? Can anybody explain what this extra battery does and what symptoms occur when it goes bad? Is there a specific procedure to follow to replace it?

zatsme7

It would be great if someone could explain the function of each battery and what symptoms would create the need of replacing a specific battery. Thank you in advance!

juanmor40

From the diagram, it seems the W166 platform can come with ECO/Start/Stop or not. Those with ECO/Start/Stop require a larger auxiliary battery (see 2 in the diagram), while those w/o ECO use the smaller battery (see 3 in the diagram).

The small battery ( 3 ) works as a backup for the shift selector and other minor electronic components in the vehicle, while the larger one helps to run more features when the car is temporarily OFF: brake HOLD feature, the ECO system itself, and other not so obvious. If the larger aux batter is depleted, you will get the Auxiliary Battery MalfFunction message in the cluster, the ECO feature never becomes active, the brake HOLD feature is not available.

I would say that is my understanding this far.