fun33

Anyone who has successfully connected TWO battery maintainers (trickle chargers) to their W222? One to the main battery and one to the auxiliary battery? MB service is telling me connecting a CTEK 40-206 MXS to my auxiliary battery would "mess with the electronics" and void car warranty. The same MB dealer tells me connecting to the MAIN Battery is approved.

I spoke to MB national customer service this afternoon. It is an "Official MB Policy" to not connect a charger to an Auxiliary Battery. MB policy states the charger could be "too strong" for the smaller auxiliary battery. MB also is concerned a charger would continue to charge the Auxiliary battery after it was fully charged. While this is MB policy, modern trickle charges are specifically programmed to eliminate both of these issues. A charger such as CTEK can be operated in the standard (large battery mode) or the motorcycle (small battery mode) with reduced amperage. The CTEK also senses when a battery is fully charged and stops the charging process.

Although the official MB policy says no charging of Auxiliary batteries, clearly many owners have used battery tenders on their Auxiliary batteries with no problems whatsoever. With the drastically reduced COVID drive time on many vehicles, many drivers are experiencing dead batteries when trying to start their cars after extended periods of non-use. MB would do us all a service if they would review and update their corporate policy on this matter. The threat of voiding your new car warranty vs your battery dying from lack of use is a conundrum.

2012 merc amg

Ya it’s kinda a bad setup having the two batteries. I’ve got my 2019 e450 in storage now long term so I’m hoping it has the capacitor rather than the second battery nobody seems to know lol. I’ve got a maintainer on the big battery. If there gonna have a second battery they shoulda designed it so the charge spills over from the big battery to the small battery.

fun33

From what I have read, the capacitors that are replacing the Auxiliary batteries have their own inherent issues. Circuit board failures and capacitor leakage. My 2018 S560 has an Aux battery as does my 2017 SL550. Neither are being driven as much as normal. I have chargers on both cars for the starter batteries but the only way to keep the Aux battery charged is to take the car out and drive it. Really need the option of putting a low amperage smart charger on the Aux but MB prohibits it or voids your warranty if you do.

fun33

Very likely you have an Aux battery and not a capacitor since my 2018 S560 definitely has the Aux battery.

2012 merc amg

Nope my 2019 E450 Wagon has the Capacitor, just verified it. I believe starting in 2019 the S class went to the capacitor too also known as the voltage regulator. part # 2059053414 This is what my 2019 E450 wagon uses. This post came from a helpful poster on the E class 213 forums. https://xenons4u.co.uk/blog/mercedes...ion-explained/

Warehouser

Just got the message on my 1 year old S560 with 3100 miles on it. Off to the dealer we go...

2012 merc amg

Ya most common problem on these cars.

Naserals

I was greeted with this message a week ago for my 6 months old s560 , and guess what? Because I know I will be getting this message every year, I replaced it myself with STX14-BS , It's a motorcycle liquid battery with same specs 😄. So far , everything looks good. I'll keep you updated. You can use the dry version , it is YTX14-BS and this is exactly the same as the original, would cost you $50-$60.

Warehouser

Thinking I may do this myself also. I can get to the battery pretty easily in the trunk. So will the wet or dry version last longer?

2012 merc amg

You can drive with message fine for a week or so. Your adaptive cruise won’t work though nor the eco mode.

Naserals

Go for the YTX14-BS, it is same specs and dimension of original. Installation should be easy , you just need to take out a few rear panels and you are good to go.

There are different brands available, check out this one



Good luck!
​​​

Sal Collaziano

I got this message today but curious if it could be simply because I haven't driven the car much since February. Only a few miles each month. How likely is it that this battery would charge back to normal capacity after a long drive or two?

emilner

Funny this thread popped up- my 2019 S560 just had this 2 weeks ago. They swapped it out without issue but a pain nonetheless...

MBNUT1

My experience was that if my car sat for a while I would get the message when I started it. If I drove it more frequently the message would stay off, however eventually the message would return more frequently and I eventually replaced the battery. Now my car sits for long periods due to the combination of the pandemic and my retirement and I don't get the message. So the takeaway is that yes it will charge but it is on the way out.

Radman991

When I returned to Florida this fall after spending the summer in RI, I got the dreaded aux battery malfunction on my 2018 S560 as well. I had trickle charger on main battery but didn’t put anything on auxiliary battery because of so called voiding the warranty. Was still under warranty so dealer replaced it without any hesitation. Problem is going forward when car is out of warranty. Not sure if I should trickle charge it or just buy the new 2021 model. Lol.

2012 merc amg

Your life sounds like mine Florida and RI. Tennis winters and Sailing Summers. Nor a bad life. Ya I don’t see why not put a maintainer in the aux batt. Make sure a maintainer though and not a trickle charger.

PatentLawyer

The aux battery was the only issue I ever had in my '18 S450. It happened during the (first) height of Coronavirus here in the Northeast and the service advisor said they were seeing a lot of it; he speculated that it was due to drastically reduced car usage.

emilner

That sounds logical, my car was sitting around far more than usual. And I know from past experiences BMWs are notorious for that. They won't change a battery under warranty unless you drive on the highway every day. What a mess. Sounds like MB might like more constant use too.

2012 merc amg

Too bad the little battery is not more accessible to put a battery maintainer on it when the car is not in use for long periods, it would be kinda a hassle to pull all those panels out every time you hooked up the battery to the maintainer. One idea might be running a quick connect lead that came out of the panels that you could just plug into to avoid removing the panels every time you went to charge it.

Mitch Alsup

554 timer, a capcitor, and a resistor powered by the green LED in the button:
Power to LED runs the timer circuit
timer waits 5 seconds after light comes on,
timer then "pushes button" via the discharge transistor
LED light goes off.

Presto:: you are never bothered again.

If you are good with a soldering gun, it fits inside the "button"

ageeltm0

good day. My malfunctioned aux battery voltage was measured after replacement and found 12.92 V!! Amps not measured though.

is it good and need some action or really failed?

thanks

Jud Chapin

Can't really tell. Batteries need to be tested under load.

vinnybenz

What was the voltage of both new and old please? I assume you took the readings before driving the car.

Mike_Metal

Some functions do not work like Distronics etc.

You can drive safely.

Have Mercedes Roadside assistance come home and replace it. I am told (Roadside assistance people) that it is cheaper than going to dealer. Go figure. I had done on my E class.

akoustic

I was able to trickle charge my Aux battery to 12.9v and also trickle charge the main battery to full. Still I'm getting intermittent Auxiliary Battery Malfunction message. I was not able to check the battery health other than voltage (I only have a multimeter for now). Is there anything else I should be doing? Will low CCA trigger the same error message? Thanks everyone...