How to replace Auxiliary battery on a Mercedes S550 (w221).

In this video you will learn how to replace the auxiliary battery on a S550 (w221). The same method can be applied on (W221) years ranging from 2007- 2013.
Supplies required:
-Auxiliary battery
-T-25
-T-20
-10mm
-flashlight
-flat screwdriver/pry tool

[@Mrlightskin2u]

Great video. And I really like the fact that you didn't cut parts out too much and you showed it. Step-by-step. Because some people like myself are a little bit slower and need to see that.

[@meetbhuller6324]

Hi, I apologize for the late response here. Thank you so much, I appreciate it. I am glad to hear you found the video helpful. I definitely understand what you mean, I am the same way, I need to watch step by step and follow along. If a video has lots of parts cut out, it makes it harder to follow along. Happy Holidays🎄🙂

[@MyTho.1]

Great help! Appreciated. I got similar problem in my 2012 SLK350. Mine has no fuse panel, but same location. Very detailed instructions!

[@meetbhuller6324]

Thank you. I am glad to hear you found this video helpful. Also, thank you for sharing that the 2012 SLK does not have the fuse panel there. I just learned something new from you! This might be knowledge for others as well 🙂

[@theurbanartist775]

I have the exact same message and I was thinking I need to replace the trunk battery. Thanks a lot, this video was right on time ✌🏽

[@meetbhuller6324]

not a problem brotha🙏! Glad you were able to find this video! Yup if you are seeing this message on the dash, then switch the auxiliary battery from the video and that solves it.

[@I_act_up]

Great video. Detailed and informative. Thank you sir!

[@meetbhuller6324]

Hi bro, I apologize for the late response here. Glad to hear you found this video resourceful. Not a problem, thank you🙂.

[@alexanderkucher2140]

Thank you very much! great video! Alex😀

[@meetbhuller6324]

Thank you so much! I’m glad you liked the video 😊.

[@ahmedkamalalkamali6929]

I like the way your demonstration Exlent job my friend For replacing MB S550 W221 auxiliary battery is quiet harder then mine W211 E240 W211 auxiliary battery located at the end of engine room passenger side , I think it is filled with AGM/GEL acid to reduce corrosion build up..

[@meetbhuller6324]

Hi, thank you, I am glad to hear you liked how the steps in the video were demonstrated. Yes it seems that on some models the auxillary battery location is harder to get too versus on some its much easier. Thank you for sharing that comment. Happy New Year!.

[@youngfinance6319]

my 2011 s550 fm radio says device not availble, does this have anything to do with it

[@MrFarmer83]

What were some of the issues you were having before you replaced the auxiliary battery? Mine is the Radio isnt working and if I dont start the car everyday seems to drain my main batteries, also auxiliary battery fault shows on dash. Hopefully changing that will fix some of my issues thx.

[@MrFarmer83]

Update switch auxiliary battery but fix issue. Benz are difficult

[@TRABBENT]

Does the auxiliary battery has anything to do with the ism module on a 07 s550..I jst took it out..

[@meetbhuller6324]

Hi, I apologize for the late response here. So I reached out to my local Mercedes Transmission specialist who is more knowledgeable with ISM modules. Hope this information below helps. The "ism module" is a unit that is bolted on the side of the transmission . The ‘ism module” is what sends Electrical signals to be able to change the gears on this vehicle. The auxiliary battery controls the functioning of the inside electronics in the car. Meaning, entertainment, dash, etc. Also, in the S class W221 Mercedes, since the gear selector(P,R,N,D) is a electronic gear selector, if the auxiliary battery fails, it can cause you not to be able to switch gears from the small gear selector that is on the steering wheel column. It depends on the model of the car, but mainly iit controls a lot of the electronic stuff in the car. It is the secondary battery in the car. I would make sure both the regular car battery and auxiliary battery in the car are good. Since if the auxiliary battery is not good, it may cause you not to be able to select the gears from( P,R,N,D). I have knowledge about the Auxiliary battery but was not 100% about the ISM so asked one of my local Mercedes Transmission specialists. The specialist did also mention that, if you are having issues with selecting gears to make sure both batteries are good, and if they are, it's possible that it could be the ISM module. If a new “ism module” is installed, it does require programming to the VIN of the car. Are you receiving any messages or errors for the ISM module? Or having any issues related with gear selecting or shifting? Do you have an auxiliary battery message on the dash? I hope this information is helpful.

[@carloschacon1979]

Do I have to disconnect the main battery to do this please let me know thank you

[@meetbhuller6324]

No you do not need to disconnect the main battery.

[@HyperSin]

Easier just to remove the fuse panel to access that battery

[@meetbhuller6324]

Hi bro, I apologize for the late response here. I will definitely try that the next time I replace the auxiliary battery. If it can be made easier, that is definitely the best. Thanks for sharing here. Happy Holidays 🎄🙂

[@mizterblicky5569]

When does this go out

[@meetbhuller6324]

According to the Mercedes Benz website, On average, auxiliary batteries have a service life of up to seven years, more or less depending on usage and driving conditions.

[@lawrenceralph7481]

Its much more accessible in a w207 e550a trunk.

[@meetbhuller6324]

Yea the trunk definitely would be more easily accessible vs under the steering column. Thanks for sharing with me!

[@KorootiAd]

What is it good for?

[@meetbhuller6324]

@korootiAd The auxiliary battery controls the functioning of the inside electronics in the car. Meaning, entertainment, dash, etc. Also, in the S class W221 Mercedes, since the gear selector(P,R,N,D) is a electronic gear selector, if the auxiliary battery fails, it can cause you not to be able to switch gears from the small gear selector that is on the steering wheel column. It depends on the model of the car, but mainly to answer your question, it controls a lot of the electronic stuff in the car. It is the secondary battery in the car. Hope that answers your question.

[@ahmedkamalalkamali6929]

BMW & Mercedes Benz finished no more , it becomes grabbed a cheep collections from Swedish Dacia and the rest fabrications from Taiwan n Chaina with cheep silly design , no more expert designer in MB or BMW as all them been terminated.. The last quality MB was W210 & w211

[@meetbhuller6324]

Hi, Sorry for the late response here.I totally agree with what you said. I feel like the older Mercedes were built with quality and for lasting. The more the newer ones, its more plastic and the quality on them just keeps going down. I agree the W210 and w2I 11 was made with quality. Thanks for sharing your thoughts!

[@MuzixMaker]

Not in a 2007 W221.

[@JohnDoe-zg8jm]

I replaced mine, still shows the warning on the dash

[@meetbhuller6324]

The auxiliary battery you replaced with, was it from Mercedes Benz dealer or after market? After replacing, have you driven the car for some time? I know sometimes it can take some driving to reset the computer and for it to pick up that it’s been replaced.

[@JohnDoe-zg8jm]

@@meetbhuller6324 thank you for your reply. It's an aftermarket battery that had great reviews as far as a replacement for Mercedes. I've put about 400 miles since then.

[@meetbhuller6324]

@@JohnDoe-zg8jm Apologizes for getting back late here. Were you able to get the issue fixed?