Just documenting my experience with the current battery in my W204. I dont put many miles on this car, drive it on the highway maybe once a month, mostly around town a few miles a day, can go 1-3 days without driving it.

Around 4-1/2yrs ago the battery in my W204 stopped holding a charge. Drove fine after using a battery booster to start it but then wouldnt start again without the booster. The battery in it was a genuine MB battery 0009823208 and from the manufacture date was 7yrs old. So I bought an exact replacement. Only when i got home from buying the battery did i realize it was already 1-1/2yrs old, probably sitting on a shelf somewhere. I learned my lesson after that experience.

The manufacture date says 03/21 on that battery post. Fast forward to last month where I let the car sit unused for 6 days and it wouldnt start, cranked slowly a few times but was pretty dead. Started right up with my battery booster. After that I noticed weak turnover when starting. Last Thursday i hadnt driven the car for 3 days and it wouldnt start again so jumped it and it drove fine. The next day I put my charger on it. Didnt drive it all weekend so today for fun I put the charger on it again and checked the voltage. It was low, resting only 12.4v, then after unlocking the voltage dropped to something like 11.6v.

Thats when I put my Ancel BM200 battery monitor on it. It lets me view the battery voltage from my phone app. When charging was done it was showing around 12.4v, but then just locking up the car the voltage dove and only went back up to 12,2v. Decided to take a drive and see what the battery was doing. So I unlocked the car and the voltage dropped way down to 10.9v, im assuming this was everything turning on, I have the foglights set to turn on when unlocking. Get in the car and it wouldnt start. Ridiculous. When driving the voltage was up around 14.8 so i can safely assume the alternator is working fine.






Heres the voltage driving around:




Stopped at Walmart and they have the Everstart Platinum AGM H7 batteries for $189 + $12 core charge + tax. Has a 4yr warranty where the MB only has a 2yr warranty. Everstart is an 80Ah where the MB is 84Ah.

* After buying the new battery the car wouldnt start (old battery still installed) in the walmart parkinglot and I had to use my booster again. That battery booster is a great investment. It only uses 2% everytime I use it to jump the car so it lasts forever on a charge.

Best thing was the manufacture date, must have just left the factory this month. I checked the voltage with my meter and its showing 12.85v. I put my charger on just for fun. Right after charging it was showing 13.26v. Waiting until tomorrow to install it. One thing I noticed on the label is it mentions charging it at 13.8-14.6v. Thats a tiny bit lower than what I was seeing while driving around.

I want to see what it shows for voltage when its installed. Because when I first installed this current MB battery I was only seeing around 12.45v, at least thats what all my photos I took are showing. I remember it being an issue thinking I should have returned it for a newer battery and not one already over a yr old.

I installed the new battery today and all is good again. So it was in fact just a bad battery, thankfully it wasnt something else.

I am very much assuming one of the reasons the old battery did not last as long was that it was already around 1-1/2yrs old by the time I bought and installed it. learned my lesson on that.

After putting the new battery on my Noco Genius 5 amp charger and letting it rest unplugged over night the battery showed 13.02v.




I hooked up my inexpensive Konnwei battery tester just to see what it would show and the readings looked great, as a brand new battery should. Now I have an idea and starting point of this battery to use down the road. I like this tester because it lets you input how many CCA the battery is and that its an AGM. The Ancel BM200 bluetooth device I use does not have these features, or at least I havent figured out how to change it.







The old battery still in the car was showing below 12v today.




Installed the new battery and connected it. As soon as i connected the negative battery cable i heard some popping noises, i really thought it was coming from the abs and I blew something in there. Thankfully that wasnt the case. After driving the car around everything seemed to be working fine, no warnings, battery showed signs of it being charged.

I did have to reset the Time/Date. Everything else in the Settings menu was as I had them before.






Not sure how accurate the Ancel unit is. But it showed the difference between the old battery and the new battery state of charge.

I thought when you placed a new battery into a MB you had to program the battery for the vehicle

This will be the 2nd battery I installed in a W204 and havent done any additional steps. The service manual doesnt mention any type of coding needed.

I believe that only newer models benefit from battery registration. For instance:

"The Mercedes-Benz W213 Battery Management System (BMS) monitors, optimizes, and protects the main 12V and any 48V batteries to ensure longevity. The system regulates charging, monitors health, and often requires registration via OBDII after replacement to avoid error codes, a faulty charging profile, or Stop/Start malfunctions. It often includes a dedicated sensor, similar to those found on eBay, that monitors voltage, current, and temperature."

The W204 does have energy management which im still trying to understand. One thing im confused about is the manual mentions the car seeming to want to maintain the battery at 80%, but when i read about AGM batteries im finding they like being kept fully charged.

I've left the Ancel battery monitor on the new battery just to see what its doing. I'm not so focused on the monitor showing the SOC since im not sure how accurate it is to my specific battery. I'm just keeping an eye on the battery voltage, seeing short trips vs long trips, how its charging.

The manual mentions a fast charge at 15v which I have yet to see, probably because this new battery has not yet dropped below 80%.

Since the old MB battery is out of the car I put it on the charger to see what it does. Seemed to charge fine until I put a voltage meter on it and was only seeing 12.65v. Thats the max the charger would get it to after repeated attempts. I let the charger do its thing until it was blinking green indicating its done charging and its now set to maintenance mode so according to the charger the battery is fully charged.

Put my inexpensive Konnwei battery tester on it and sure enough its saying to replace the battery. So with the readings it showed on the brand new battery and now this reading of the dead battery its safe to say its pretty accurate.



The MB battery has a little window that im assuming glows green if the battery needs to be replaced. But its not green. I'll have to look more into what its exactly for. It was actually covered by the label when I got the battery so I peeled it back to check. Wonder if the new battery has one.

I was moving the old battery around on a dolly and noticed the little light was coming on when I had it tipped back. Not sure if its a light or just a reflection. Also heard liquid sloshing around in it. Guess its just triggered by detecting a low level of acid inside.

It’s just a reflection of the bottom of a little tube when the acid level drops below it. Very simple and reliable.

Thanks.

Thanks to TimC300 for the detailed information. Our 2013 C250W204 was purchased new in November 2012. In February 2022, with about 28k miles on the odometer, I noticed a slower than usual crank, though the car still started without hesitation. That’s when I decided to take the battery to Wally for a replacement. Good call on my part, because the EverStart replacement part number listed on their website was wrong! The correct fit for my car is similar to yours, an AGM Group H7, except mine is labeled Made in S. Korea. On the bright side, I saved $13 in core charges by handing in the old battery.

As for the sticker, I seriously doubt the date on it reflects the actual manufacturing date. At the Wally I visited, battery storage is limited to staff only. I can only assume the staff grab a sticker with a recent date and place it on the battery to make it seem fresh. I’m not expecting the EverStart replacement battery to last as long, but I’m keeping my fingers crossed.


Original Battery


EverStart Platinum AGMH7

WM battery warranty starts when the battery is installed per your receipt. It’s 4 years, I think. The sticker is put on top of the battery when it is sold or installed because most people don’t know where the receipt is 3-4 years later. Walmart sells a lot of H7 batteries so they are almost always fresh.

When I bought the Everstart battery at Walmart the lady scanned the serial number label first and then the sku label so both are listed on the receipt. The serial # starts with "EP" which from my research means the battery was manufactured by East Penn manufacturing which seems to manufacture many other brand batteries. It seems the little round sticker with the date 3/26 may be the actual ship date from the manufacturer. The battery does seem "fresh" from my testing and battery monitor readings.

I still have the Ancel BM200 monitor hooked up so I can get a good understanding of what the car and battery are doing. I'm starting to see patterns when driving, how the voltage fluctuates when coming to a stop, idling, then taking off.

Ignore the recall info below, I was just looking to see what other brands East Penn makes.

The new Everstart battery has been working great.

Finally stopped back at the Walmart to return the old battery for my core charge back. They have a rack off to the side of the return desk to drop off old batteries and oil. Picked up some oil while there and noticed the H7 AGM batteries were all sold out. They were pretty well stocked up on other batteries. Makes me think think the battery I bought really was fresh.

Bottom right corner sold out.

Hard to complain about getting 5 years of life from the OE battery. Mine crashed at 42 months. Your new battery with a 4 year warranty for $190 prorates to less than $50/year -- about the same as half a tank of gas. Well worth the assurance that your car will fire up each morning.

Havent driven the car in over 4 days and when I checked the battery it showed 99% charged. For me that is fantastic as i'm used to having the battery voltage always go down when parked.

Was this after external charging and with sleep mode enabled, or just normal car charging and parked?

This was after I drove the car on the highway for a few hours over the weekend. Got home and parked the car. Walked to the car Thursday and checked the battery readings before unlocking and thats what it showed.

When I had the old battery in I would see the voltage slowly drain for some reason.

I was just looking thru the saved history on the battery monitor and saw something interesting from last weekend when I took a trip to visit my parents. Drove the same highways to and from, drove the same speeds roughly except for hitting some traffic on the way there. The charging profiles look different, voltages look lower on the drive back. Also noticed just how much the battery is drained from just opening the doors and trunk a few times not even putting key in the ignition.

Its also nice to see while the car is parked the voltage stays about the same unlike with the previous battery the voltage seemed to slowly drop every day.

Something i just noticed when reviewing the saved battery info is how with the previous battery the voltage dropped and stayed lower when the blower ran after the car was parked. With this new battery I can see the voltage dip indicating the blower turning on and running but then the voltage appears to bounce back up to the level it was at before the blower turned on.

Unhealthy vs healthy battery, im assuming.

Previous battery back in 2023. Battery was around 2yrs old at that time.



New battery around 2 months old according to the manufacture date.

Your old MB battery is clearly done, made worse by the fact it was already a year and a half old when you bought it. Light daily driving also prevents it from getting proper charge cycles which accelerates the decline. The Everstart Platinum AGM is a solid replacement, fresh from the factory, good resting voltage, and a 4 year warranty beats the MB's 2 year. The 4Ah difference is negligible. Your alternator is fine at 14.8v so once the new battery is in you should have no more issues.