Looking for Group 48 Battery with 74aH rating

Status
Not open for further replies.
Joined
Aug 30, 2004
Messages
31,869
Location
CA
Application is a 2012 MB C250.

Most C-Classes of this generation use a 94r battery, but this particular vehicle uses a group 48. However, all of the group 48s I can find carry a 70aH rating, not 74.

This is the original battery from the vehicle:




Upgrading to a 94r battery would require new hold down hardware and I would like to avoid this if possible.

Any ideas?
 
Last edited:
Is it a listed requirement from MB to have 74 aH?

Unless there's a special case, the aH rating of a starting battery is not super important. The aH rating of lead-acid batteries is measured at a slow discharge rate, usually over 20 hours for deep cycle and 10 hours for starting batteries. This may be useful for running light to medium loads over a long time, but not for running an engine and accessories in case the charging system suddenly fails.

The faster a battery is drained, the lower the efficiency and the less apparent capacity it will have (the Peukert Effect). The reserve capacity (RC) is a better measurement for a battery in automobile service, as it is how many minutes the battery can sustain a 25 amp load before it discharges below 10.5 volts when at a temperature of 80 degrees F (26.7 degrees C). 25 amps is a pretty typical load of a car with engine running and headlights on, and below 10.5 volts many systems like engine management and transmission controls will begin to malfunction. RC is a good test of how far a car with no charging system can be limped along at night before becoming inoperable.

My guess is any quality brand group size 48 or H6 battery will fit your application. If the car was ever using anywhere near the full aH capacity of the battery, it would be destroying them in a matter of months since lead-acid chemistry does not tolerate repeated deep cycling like that.
 
I wonder if that spec is fudged so that you buy it from MB? All the group 48 batts i see are 70ah. I'd just go with a reputable brand that has enough cca.
 
You could contact Exide, who has links to First National Battery in South Africa, shown on your pic of the battery, and see what Exide recommends.

http://www.exide.co.za/what-we-do/

There appears to be only one 74aH 20 hour capacity battery listed in their Products section.

http://www.battery.co.za/products/automotive/passenger-vehicles/?rangeID=3&batID=66

Personally for only 5.4% difference, I'd just get the Bosch Group 48 (H6) AGM at Pep Boys while it's 30% off instead of chasing something from another continent. I put one of these in my wife's Mustang as an upgrade to the factory Group 96R and it's working great.

Pep Boys Link
 
74 aH until what happens? The battery reads 11.5 volts? Car fails to start? At what temperature? After what charging voltage? At what discharge rate?

As specs go Mercedes may be playing a different game than the aftermarket.
 
Thanks everyone.

You folks are probably correct that 70 aH vs 74 aH does not make a difference in the real-world. However, Euro cars have very finicky charging systems which use the battery's aH rating to determine the correct charge rate. For instance, BMW requires re-coding of the vehicle if you change from a standard battery to AGM (or vice-versa) and/or if you install a battery with a different aH rating. I scanned this car with my Autel and did not see an option to re-code the car for a different battery type or aH rating, so it is possible that MB's charging system is not as picky.

Based on the car's VIN it looks like there are 3 possible hold-down brackets depending on the battery size. Unfortunately there is no way to tell which hold-down applies to a particular battery size - that is just the nature of MB. MB only lists battery part numbers in their database, not group sizes. I think I need hold-down #204-628-01-41 but I am not entirely sure. The hold-down bracket is a few days away.

However they did have plenty of the unicorn 74aH rating batteries in-stock for $162 msrp.
 
Last edited:
What does the customer want? More Ah is a good thing in moderation - but if the goal is to get a bigger battery for easier availability and if the customer agrees with it, I'd swap in the new bracket.

Otherwise, I'd install the 74Ah MB battery. The good thing about German cars for the most part that the battery lives in the trunk or under the back/front seat and it's decently protected from temperature swings. Now if Mercedes is using a "micro-hybrid" charge on deceleration system like BMW and Hyundai does, well the battery will still be punished.
 
This one lives under the hood.

Owner decided to go with the MB battery. Not sure who makes it- there are no telltale markings on the battery. There isn’t even a date code. The parts guy said Interstate is the distributor, so maybe it is a Johnson Controls battery?

 
How about under that MB sticker in the upper left area? Looks like another sticker underneath that might have some info.

What kind of warranty does that battery come with? Interesting no date code.
 
Originally Posted By: Nyogtha
How about under that MB sticker in the upper left area? Looks like another sticker underneath that might have some info.

What kind of warranty does that battery come with? Interesting no date code.


If the battery was for my own car I would have peeled off the sticker to check, but it is for someone else's car.

MB policy is 2 yrs/unlimited mileage, no pro-rate.

"2.2 Any replacement battery purchased on or after August 1, 2000 at total customer expense is covered for a warranty period of 24 months, unlimited mileage from the date of purchase. Warrantable repairs will be made at no charge for parts and labor when performed at an authorized Mercedes-Benz Center (Passenger Car or Light Truck, as applicable). "

https://www.mbwholesaleparts.com/warranty.aspx
 
Last edited:
Grey case could well be made by JC but could possibly be a East Penn... JC has the lines that are tightly packed together that run horizontally around the front and sides of the case. Whereas the East Penn battery does not have that at all.
 
Originally Posted By: The Critic
The parts guy said Interstate is the distributor, so maybe it is a Johnson Controls battery?


Sounds just like Mazda. We order batteries on our regular parts stock order and an Interstate truck shows up a few days later with Mazda labeled batteries. Wonder if their fluids come from Excelda too.
 
The sticker on the positive terminal cover looks like a JCI - but it doesn't have the same cover as US/Mexican made DIN sizes. Looks like JCI might have brought in a Varta for Mercedes.
 
Status
Not open for further replies.
Back
Top