Auxiliary Battery
Thread Starter
Newbie
Joined: Feb 2010
Posts: 2
Likes: 1
06 r350
Auxiliary Battery
Hi all, new to the forum and need help locating the Auxiliary battery on my 06 R350?!?! I've located the main battery under the passenger seat and see a fuse block on the cross member behind the battery but do not see where the Aux Battery is. Can any of you guys help?
Thanks in advance. Cheers!
Thanks in advance. Cheers!
Thread Starter
Newbie
Joined: Feb 2010
Posts: 2
Likes: 1
06 r350
Found it!!! it's under the right passenger footwell in case any of you dare to replace it yourselves... will have to remove door moldings and pull up carpet to get access to and remove the panel (not battery cover but actual false floor)
Super Member
Joined: Oct 2008
Posts: 861
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From: Fairfield county, CT.
2004 Ran SRT-10,2007 S550,2016 E400c
Super Member
Joined: Oct 2008
Posts: 861
Likes: 3
From: Fairfield county, CT.
2004 Ran SRT-10,2007 S550,2016 E400c
Just make sure that the batt is being charged.. Ive seen a buch just go bad but ive also seen some go bad from the front sam stops charging them..
Easy test is to monitor it with a meter and make sure you see 12v at some point.
Or if you have access to a sds diag system you can activate the charging of the aux batt. and then check.
Easy test is to monitor it with a meter and make sure you see 12v at some point.
Or if you have access to a sds diag system you can activate the charging of the aux batt. and then check.
Junior Member
Joined: Mar 2009
Posts: 16
Likes: 3
From: North Carolina
2006 R350, 2009 E550, 2015 GL450, 1981 HONDA CB750F SuperSport
Images of location of R350 Aux battery
Here are some pictures to show the battery, its location, and a generic replacement from batteries plus.
I strongly recommend when making this replacement, to permanently relocate the aux battery next to the main battery by creating a pair of extension wires about 1.5 foot long and pass them from the current location, going under the carpet to the new location next to the main battery where there is ample room for a standard UPS battery like a 1270. Note: You'd have to find a way to anchor whichever battery you use.
Pull off the door moulding and foot panel
Push the Passenger footwell plastic panel out of the way without cracking or completely removing.
Remove the 4 plastic nuts holding down the fiberglass panel and lift it. It rests in a slot towards the front. Nuts are only on the back and sides of it.
And here is the battery held by 2 similar plastic nuts one towards the top and one in the deeper bottom side. Easy to get to but not easy to see.
Original battery compared to a replacement battery. 10mm wrench for size. The replacement happened to have its terminals the other way around, but the existing leads were equal in length so it was no problem hooking it up.
I strongly recommend when making this replacement, to permanently relocate the aux battery next to the main battery by creating a pair of extension wires about 1.5 foot long and pass them from the current location, going under the carpet to the new location next to the main battery where there is ample room for a standard UPS battery like a 1270. Note: You'd have to find a way to anchor whichever battery you use.
Pull off the door moulding and foot panel
Push the Passenger footwell plastic panel out of the way without cracking or completely removing.
Remove the 4 plastic nuts holding down the fiberglass panel and lift it. It rests in a slot towards the front. Nuts are only on the back and sides of it.
And here is the battery held by 2 similar plastic nuts one towards the top and one in the deeper bottom side. Easy to get to but not easy to see.
Original battery compared to a replacement battery. 10mm wrench for size. The replacement happened to have its terminals the other way around, but the existing leads were equal in length so it was no problem hooking it up.
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Joined: Jun 2013
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From: alicante, spain
mercedes 'R' class 320.
command centre failure
Many thanks to this site, I have just resolved my issue I had with my command centre failing to respond to any operations, ie, no phone, no sat nav, no cd player, nothing! although I could change only radio stations, and volume on the steering wheel controls, anyway, having scrolled through this site and reaping info, I finally found the main battery tucked away under the passenger seat, ******* to get at, but managed to expose one terminal, disconnect it for a couple of minutes, then reconnect, and hey presto, a result with everything working again. I have recently purchased an 'R' class, 2007, 320, hope this helps others out there. Regards,, Jack. 
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Many thanks to this site, I have just resolved my issue I had with my command centre failing to respond to any operations, ie, no phone, no sat nav, no cd player, nothing! although I could change only radio stations, and volume on the steering wheel controls, anyway, having scrolled through this site and reaping info, I finally found the main battery tucked away under the passenger seat, ******* to get at, but managed to expose one terminal, disconnect it for a couple of minutes, then reconnect, and hey presto, a result with everything working again. I have recently purchased an 'R' class, 2007, 320, hope this helps others out there. Regards,, Jack.
And it bypasses the fuse in the fuse box?
Newbie
Joined: Jun 2013
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From: alicante, spain
mercedes 'R' class 320.
HI, ODIOUS, I´M SORRY, CAN´T ANSWER THAT, BUT I SEE ONE OF OUR CHAPS ON HERE SAYS IT IS PURELY THERE TO POWER UP THE ´PARK´ WHEN MAIN BATTERY IS DEAD/DICONNECTED, I´M NEW TO THIS VEHICLE, SO ALSO AM LEARNING!!
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From: Akron, OH
2006 R350
Newbie
Joined: Jan 2014
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2006 Mercedes Benz R350
Thank you
Thanks for this thread, no MB dealers near me(over 160 miles away) and almost $200 for replacing an $11 battery is crazy. Btw, I had to remove 5 nuts to get the fiberglass floorboard up. Oiled them putting them back in so that the hard to reach ones went on and hopefully com off better in another 11 years.
Last edited by bubarsmith; Apr 13, 2015 at 04:47 PM.
Newbie
Joined: Sep 2017
Posts: 3
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R350
R350 Auxiliary Battery Install Pics
Hi Everyone, I enjoy the posts and info. As a way to contribute, I recently changed out the auxiliary battery and took a few pics. I moved the seat all the way back and removed the passenger foot panels. The battery sits in a bracket underneath the carpet and board. I did not have to remove the seat at all and the battery was relatively easy to get to. Hope this helps!
Junior Member
Joined: Jan 2018
Posts: 45
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2006 R500
I just replaced the main battery under the seat, it was 6 years old. I am still getting that little warning battery light, usually first thing in the morning, but it eventually clears out the light. Would this little Aux battery under the footwell be the cause of this? Great thread and pics BTW.
Leo
Leo
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2006 R500
Newbie
Joined: Feb 2019
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R350
I replaced the battery under the carpet, and still getting the warning light. The battery measures 12v dc and no resistant at the positive/negative lead from the SAM. Is there a relay between the battery to the SAM? I checked with car started.
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From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
Did anyone do a scan with iCarsoft or other Mercedes scanner and see if there's an error that needs to be cleared?
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Im actually surprised these SLA batteries can last 10+ years. These are the same type that go into my UPS and those dont last more than 2-3 years.
Replacing them with consumer grade SLA will likely mean we'll be replacing these batteries again in a few short years.
Replacing them with consumer grade SLA will likely mean we'll be replacing these batteries again in a few short years.
Last edited by ODIOUS; Jun 3, 2021 at 06:24 PM.
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From: Scranton pa
2006 mercedes benz r500
