pca7ggr

A source for a battery for our MB is WalMao for $123.13:

http://www.walmart.com/ip/16782659
FREE battery testing and installation at your local Walmart Auto Care Center
Free lead-acid battery recycling at your local Walmart
3yr free replacement

cetialpha5

That I believe is a standard lead acid battery. The other ones quoted earlier are AGM batteries which tend to last longer and don't tend to vent hydrogen gas so the terminals are less likely to corrode. Personally I would prefer to get an AGM battery instead of a standard lead acid one, they're not much more money.

thefisch

Yeah, I did see that Walmart one, but it wasn't AGM and not in stock anyway. Besides the Bosch AGm is just $5 more after rebate with one additional year free replacement.

75gasgas

Hi there folks,

I replaced the battery in my 2011 E550 yesterday. It had been almost 4 years exactly since the inservice date. I took advantage of the Pepboys sale on the Bosch battery, thanks for posting that up. Everything went very well, I had a 9volt ORBII memory savor from a previous job so, I plugged that in and began the install. It turned out to be very easy and straight forward. The difficulty I ran into was lifting that behemoth of a battery into the engine bay!! As far I can tell the only thing that reset was the trip odometer. Thanks again to thefisch for posting up the breakdown of the different battery options and costs, that made the decision of which battery to purchace a no brainer.

KEY08

Good for you. These H8 batteries weigh a ton and the hardest part is lifting it into place. Almost need a crane. LOL

thefisch

Happy to share the deal and glad someone used it. This reminds me I need to send in the rebate form. I hate rebates.

I did not use a memory saver when I changed mine. I lost no settings - only my 'from reset' went back to zero. At any rate, you got a fresh battery now.

Just curious, did you check the battery voltage before or after you installed it?

75gasgas

I just ran out and checked the voltage, 12.31 on the old battery and 12.47 on the new. Are these similar numbers to the ones you found?

thefisch

Those are in the ball park. Mine was 12.36v this morning Here is another thread about checking battery voltages where a couple folks posted some results. I was expecting something like 12.7v based on 12V battery state of charge information. Not sure exactly why, but these batteries tend to run lower voltage. So long as it works, then it's doing its job I guess.

clymber

Just wanted to say thanks to all on this thread! Replaced battery on 2011 E 550 coupe no problems.

thefisch

Well after almost 3 trouble free years since installing a replacement battery, I have had two instances weeks apart in the last few months where the car would not start and needed a jump. Car has started fine all the other days. Going to have to keep an eye on it. Given our Honda goes through conventional batteries every 2.5-3 years (just installed it's 4th battery before its 8th year anniversary) in this FL heat, maybe these AGM batteries won't last that long either for me down here. Still have a year left on the Bosch warranty so I'll get a replacement if it keeps failing. By the way, I bought a portable jump start pack after my Honda's battery failed on vacation a few months back and they are great. fired up my 5.5l V8 both times without an issue.

DFWdude

Check the fluid level above each cell to be sure the cells are covered, and add distilled water to the bottom of each shaft as needed. That could account for your intermittent starting issues.

Your FL heat (like here in TX) plays havoc with evaporating water. People are told these are "sealed" batteries... but they aren't really.

thefisch

I can open the caps on the conventional battery in the Honda but the Bosch AGM in the MB doesn't have removable caps on it. Plus, it has a big warning that battery is not serviceable and do not attempt to open.

Oda112

Have you been topping it off with the Ctek from time to time? My 3 year old MB one has been fine after going trough a week of the AGM treatment on the Ctek. It failed to even crank the car last fall, talked to you guys here and was ready to buy a new one but decided to try that charger first. It's been running fine ever since. The problem might be the PC, polar bear hugging charging algorithm MB uses in the W212. If you don't drive your car long distance often it might just be discharged because of that. I'd try a few charge cycles before paying for a new battery, just make sure you have a proper cooling solution for the Ctek (or whatever brand you're using), mine got to 155F yesterday while charging the battery.

thefisch

So I charge my battery using the CTEK in normal mode every 6 weeks or so just out of habit. I have a calendar reminder set for every 6 weeks for when I check fluids, tires, etc. and hook up the charger for good measure on both cars even if battery is doing fine. What do you mean by 'a week of the AGM treatment'? Did you leave the battery connected to the charger for a week? Did you run the charger in RECOND mode?

That charging algorithm is definitely the issue. When I use the CTEK to charge the battery in my Honda, it is done in a few hours meaning the battery had a higher SOC to start with whereas my MB takes about 8 hours to complete a charging cycle. I observed this difference constantly for the longest time. Threads like this one spell out the battery eating smart alternator that MB employs - http://www.benzworld.org/forums/w212...-factoids.html So whatever recharge the battery gets from the CTEK is probably eaten up during the next few trips to save fuel. I didn't realize the chargers could get that hot. My charger doesn't seem to have a heat problem - it is only warm to the touch from what I have noticed as it sits on the garage floor.

Oda112

I meant the Recond mode. I ran it for almost a week. The first time it took it 2 days to get to the full charge phase, step 7 ( I have the 8 step Mus 4.3 - https://smartercharger.com/wp-conten...al-mus-4.3.pdf). Then I disconnected it, let the surface charge dissipate, started the engine, let it run for 30 seconds, turned it off and repeated the Recond routine. The second pass lasted for almost 2 days, did the engine start again. The third Recond cycle was done in 1 day +/- a few hours. In total I repeated my routine 5 times. I have been topping it off every couple of weeks and it's been working very well ever since. Now I think it takes it around 4 to 8 hours to go from step 4 ( absorption) to step 7, depending of how much I drive it around town. Short distance driving will drain the battery very fast. The charger itself gets really hot during step 4, might be because my garage is not cooled.

thefisch

Thanks for the info. I have the same charger but haven't tried the recond mode, mostly due to the inconvenience of having to disconnect the battery from the car due to the higher voltage that uses. And based on your experience, I would have to plan on not using the car for a couple of days for that mode to complete. Since I still have 1 year left on the Bosch replacement warranty, I will see how it goes over the next few months. If this pattern continues, I will probably due a warranty swap while I still have that option.

Oda112

I never disconnect the battery. I permanently hooked up the extension the Ctek came with to the positive and negative terminals of the battery and it's been safe so far. No errors or any sort of issues and it only takes a few seconds to hook it up, just make sure you don't tap into any lines after (looking at the lines coming in to the box from the battery) the prefuse box.
In your particular case, I would get a new battery from Bosch if possible and then do the charging routine periodically though, unfortunately it seems like the W212s will prematurely kill batteries regardless of brand or capacity ( or it's the FL heat, I've no experience with that yet so can't dismiss it altogether). The only issue you might have with that is them not honoring the warranty if they find the battery can hold a charge. That's why I suggested trying the recond cycle first. As a side note, the first time I used the Recond program, I could hear louder sizzling inside the battery. That didn't happen the 2nd, 3rd of 4th time, when it was still audible but noticeably quieter than the 1st cycle. There was no visible output in the battery exhaust vent throughout the cycles either, that's another aspect to be careful about if using the recond program.

thefisch

Yeah, I use the normal mode when the battery is connected to the car. The RECOND mode ups the voltage to over 15 volts which exceeds the MB recommended 14.8 volts for my W212. Glad to hear that hasn't caused you any issues though.

Oda112

I personally think the 14.8 limit is more like a guideline or a suggestion. You can go over it as long as you don't have the car running ( I did it a couple times and everything is still fine). One of the other things I do is put it on the regular AGM charge mode and listen to music in the car ( the Logic7 sounds really good and I don't get yelled at since no one outside the car is bothered by it). I've done this extensively over the past 6 months with no issues yet (the Ctek heats up but that's it).
Also, if MB doesn't want anything over 14.8 V into their cars why do they sell an overpriced version of the Ctek 4.3/7.2 as an official battery maintainer? Maybe they deactivate the Recond funtion on those, I don't know.
I understand how you want to follow their rules to the letter just to be on the safe side and I respect that. I like bending the rules where I think possible, like in this case. A 3 year life span for a brand new battery doesn't sit well with me.

ItalianJoe1

Part of the issue is with the charging strategy of the car, they aim to keep the battery at about 80%, this is to allow room for the car to reclaim energy when coasting or whatever situation and not waste the mechanical energy otherwise. The reality is, a partially charged battery is just closer to being dead, and results in shorter battery life as we all have noted. The older cars before the advent of these LIN controlled alternators or just before the logic that keeps them not at 100%, the batteries seem to last much longer.

I've attached a GF doc that has some basic function info on the energy management, if any of you technical guys are interested. It's from an early 212 but the logic is the same on every modern MB.

cetialpha5

It's also not clear to me where you guys get that 15 volts. Are you actually measuring the voltage when it's connected to the load or is that the voltage it's at without a load?

Oda112

That's the coolest pdf I've seen on mbworld so far! I'd owe you a case of beer if you could produce one that describes what's going on in the brain of the airmatic and adaptive damping control unit.

Oda112

I think he was referring to the max voltage the control units in the car are rated at when he was talking about the 14.8V max input. The MB alternator charges up to 15V for the fast charging cycle (a very interesting read thanks to italianjoe) for the first hour of driving or until the battery reaches 80% and depending on outside and battery temps. Load dependent charging is described further in the pdf.
The Ctek charger we were talking about charges up to 15.8 V in the recond mode and 14.7 on the normal one. Thefisch was reluctant because of the 15.8 V on the Ctek, I've used it while the battery was connected to the car and had no issues.
I don't know where the 14.8 V came from, but I trust thefisch isn't inventing it. Knowing MB I can see them coming up with a story like this to keep us peasants from tinkering with their high precision machines.

thefisch

Me too.

I got the 14.8 volt from the 2011 E class manual section about charging the battery. Also in my car, I have viewed the voltage values on comand while driving and seen the voltage max at 14.7v at WOT. So I figured that was the ceiling MB recommended. It's not a big deal to disconnect the battery if I decide to do the RECOND mode. Just not as convenient.

ItalianJoe1

I'll find and post one when I get home, the work computers don't let me easily save a PDF and most functions are locked so I can't do much about it.