Auxillary Battery Malfunction (Trunk) - Easy/Cheap Replacement DIY




Link of battery used in description. $40 replacement vs $130 OEM battery, and of course not including dealer premium.
Hope this helps.




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I know the reasons behind venting and whatnot, so I will leave it up to individuals choice. Between this and pricier alternative replacements without vents, there were no reported issues.
If you do not know, venting is important for batteries in passenger compartments; because this is in the trunk, *technically* it counts. While the battery style is slightly different (eg agm etc) if you are more comfortable with OEM battery, you can still purchase direct replacement on Amazon.




I have AMG batteries with no hole in them and looks like the one here doesn't have it neither?
Why some AMG batteries have vent hoses? Beats me. I would not loose sleep over it, especially with battery in the trunk.




It cost me over $70 just to buy gas yesterday in CA
I don't get it




It's evident that there are thousands of people using similar batteries, if there was a problem, we would definitely have seen it. People are more likely to post when something goes WRONG than write a good review.
I'd be inclined to find a Yuasa battery of similar spec. My experience with these off-brand batteries on Amazon is really hit or miss (not with Start/Stop).... I bought a few AGM VRLAs for my dual sport bike and they last all but 6 months before not wanting to take a charge ($40 vs $100 for Yuasa).
Edited to add: Auxiliary not auxillary




Typical is that owners put Zerex coolant for $5 savings. I often drive in 120-130F environment and my cars never overheat, even when they do have high mileage.
I just got $3800 estimate for my Sprinter exhaust leak repair. Did I go for it? NO WAY ! I am buying $170 flex pipe and will have muffler shop cut off the old one and weld aftermarket copy.
When it comes to this battery - again this is no spill battery that doesn't have vent. Maybe it is better design than OE battery?
Regardless the MB batteries don't have good reputation, so if that one will last 3 or more years it makes lot of sense. Not like aux battery failure will stop you in your travel.
One more note - if you have alarm system in your house, you do have 1 of those batteries somewhere in your closet. Is it vented?
Same with computer backup power.
Last edited by kajtek1; Apr 2, 2021 at 10:01 AM.




You guys and Geek had constructive criticism. If people didn't know, they learned something, as well as now you've got the idea to pursue a different option. That's why a forum is best, it's /usually/ people who know more things in depth about the car than the average owner, or "Facebook group" member. If I wanted those kinds of low level comments, I could go elsewhere. What am I supposed to say, my car is more expensive than his? Does that help anyone? Nope. Constructive criticism is different than shallow criticism.
Obviously I will be the test bunny for this battery. You can take a look at my posts and "thanks" and you'll see I'm not going anywhere. I'll gladly update this thread when anything changes. As for now, I'm confident in the replacement.
Last edited by Adi-Benz; Apr 2, 2021 at 11:36 AM.








Edited to add: Auxiliary not auxillary

I don't think the air in area around the spare tire is at all vented the way both trunk sides are with flaps.
The Ingineeers idea to route AGM gases outside serves as warning. These AGM batteries can see deep cycle duties and some over-charge if the car charging system goes crazy. There is no battery sensor on the rear auxiliary to measure Temp, current to stop a runaway condition.
The load current out of this battery is in the 30 to 50Amp range when it supplies the whole car minus the starter 100Amp. load.load.... keeping a proper vent tube looks like a good policy.
😎




that relay is tucked away as well
I believe air is exhausted underneath the rear window from the cabin into the trunk and out the rear wheels. There will never be enough buildup of gases for anything to occur. You're really looking for a perfect formula; I'm not saying it can't happen but I don't think exaggerated circumstances will occur in most cases
Last edited by Adi-Benz; Apr 2, 2021 at 02:04 PM.








Here the Amp/hour load rating is key
Last edited by CaliBenzDriver; Apr 2, 2021 at 02:15 PM. Reason: matching criterias















