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2002 C240
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Discussion Starter · #1 · (Edited)
My car is 2002 C240. If I knew MB's Roadside Assistance, I would call them up and pay $150 to get the battery changed. But, I didn't know. So I replaced the battery myself.

In doing so, I found something interesting. The original battery was Group 49 (15L x 6 7/8W x 7 3/16H). The dealer's price was $145. Advance Auto Parts had AutoCraft Titanium Group 93 (15L x 6 7/8W x 6 7/8H) for $95 - 20% off. That's saving about $69. The dimension is the same except the height. It was cheaper and had better rating: CCA 850, CA 1000, and 150 RC. The original Group 49 battery had CCA 850, CA 950, and 100 RC. Here is the link of Group 93 battery.

Advance Auto Parts: Battery, Group Size 93, 850 CCA by AutoCraft Silver - Part 93-1

I installed the battery with Group 93 last night and the car started with no problem. I haven't driven the car long distance, yet.

Here is the question.

1. Has anyone install Group 93 instead of Group 49?
2. Is it okay to install a battery with higher CA and RC?

Thanks.
 

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'07 C280 4matic, '06 530i, '98 ML320
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CCA and CA are not a good way to compare batteries for cars. Ampere-Hour (Ah) numbers should be used for comparing the batteries.
As long as you get the 100Ah, you are good to go.
Warranty should be considered in choosing the battery. Cheaper battery with lesser warranty period won't be good 'value' in the long run.
 

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2002 C240
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Discussion Starter · #3 · (Edited)
CCA and CA are not a good way to compare batteries for cars. Ampere-Hour (Ah) numbers should be used for comparing the batteries.
As long as you get the 100Ah, you are good to go.
Warranty should be considered in choosing the battery. Cheaper battery with lesser warranty period won't be good 'value' in the long run.
Thanks for your reply.

pcy, where did you get 100Ah rating?

Why MB's original battery doesn't have any rathing info label? May be I missed it. I will check it again later tonight. I called local MB dealer and they don't know what the Ah rating on their ORIGINAL battery.
 

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'07 C280 4matic, '06 530i, '98 ML320
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MB dealer doesn't know the Ampere-Hour rating of the battery on your car?
I'm not surprised.

EPC shows the AH of the battery. Look at the attached picture - specifically the wording below the word "BATTERY". It clearly says 12V/100AH.
 

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2002 C240
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19 Posts
Discussion Starter · #5 · (Edited)
pcy thanks again.

The MB old battery had 100Ah rating. The battery from Advance Auto Parts didn't have Ah rating. And, I noticed the window won't pull up with one touch of the window button. So, I decided to put MB OEM battery.

I put old battery back in. I called MB roadside assistance. They came in 20 minutes. The technician checked and charged the old battery and he said my battery was good. He said something must drawing the battery out and he suggested to take to MB dealer to check it out. But, I was skeptical because I know the battery is bad. It is 4 years old. The voltage was like 6 when I measured it with a voltage meter. So I just asked him to install OEM MB battery. It cost me $145 + tax. May be he is right. Alternator, seat control module, or something else might be bad. I will search the forum how to check the current draw.

After intalling MB OEM battery, the window does pull up with one touch of the button. I guess it must be the Ah rating difference.

Thank you.
 

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'07 C280 4matic, '06 530i, '98 ML320
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Glad to see your car is back on the road and you are able to use one-touch feature for the windows.

For some parts, I don't mind paying premium to get MB part. Battery is one of those items.
Original batteries on these cars last 9 to 10 years without any problems (unless you drain the battery completely by leaving a light on).
 

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2002 C240
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Discussion Starter · #7 · (Edited)
pcy thanks again.

The MB roadside assistance tech guy was correct. There is a battary drain issue. New battery drops down to 12.2 after 24 hours. I have a strong feeling that seat contro module is gong bad again. It was replace 2.5 years ago under a warranty.

I need help on connecting a backup battery so that I don't loose Keep Alive Memory (KAM) while I check the current drain.

This web site (Diagnosing A Car Battery That Runs Down) says "Plug a battery backup into the cigarette lighter (or attach a backup battery or power supply to the battery cables) to protect KAM while disconnecting the battery cable.
"

How and in what order do I connect cables from the backup battery to the existing battery cables? Can I use other car's battery as a backup battery? After connecting the backup battery, which cable red or black do I use to test the current?

Thanks.
 

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2002 C240
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Discussion Starter · #9 · (Edited)
I found out that two places are draining my battery. A fan in overhead control module and seat control modules (don't know which side. I pull out both sides).

Can anyone tell me how I can replace the fan in the overhead control module? How to take out the cover? and etc...

And, I noticed another problem perheps I produced more problems... One-touch feature for the window wouldn't work again and SRS warning light came on. It seems these problems started after I disconnected (-) cable to check the current drain. I did take out the key from the ignition. Alternator seems working fine. The charging voltage is above 14V when the enging is on. I will probably buy Carsoft multiplex scanner to reset SRS light. But, for the one-touch window feature problem.... I don't know what's causing it. Using MB OEM battery didn't solve the one-touch window feature problem at first place. I would appreciate any idea.

Another observation... It seems like I always get small sparks when I connect (-) cable to the battery post. (engine is off. the positive cable is still connected) Is small sparks normal? What does this mean?

Thanks.
 

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'07 C280 4matic, '06 530i, '98 ML320
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Since you've disconnected the battery, you will need to re-sync the windows and the sunroof (and may be other components). Procedure for re-syncing the windows and the sunroof is documented in the owner's manual. Or you can search on this forum.
 

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2002 C240
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Discussion Starter · #11 · (Edited)
measuring battery drain correctly

I may have measured current drain incorrectly. I am using Equus 3320 multimeter. Here is what I did.

1. Disconnected the negative cable from the battery.
2. Selected DCmA function on my multimeter. This function has 315mA/250V fuse and measure from 0 to 200 mA according to the multimeter's manual book.
3. Connected the multimeter to the negative cable and to the negative terminal in series.
4. Reading says 0.011 I wasn't sure if this is correct so I did next step.
5. Selected DC10A function on the multimeter. This function is unfused measure 0 to 10 A.
6. Connected the meter in series again.
7. I get small sparks and the reading is 2.0 A.

Q1. Is the second reading correct?

I red some article on the Internet saying that "When the battery cable was disconnected the vehicles electronics lost power, these devices will draw a higher current when they are reconnected (probably, when I connected the multimeter in series). The current will drop as the numerous electronic devices awaken. On some late model vehicles this may take 20 minutes or longer."

Q2. What is the correct way of measuring parasitic current drain on MB vehicle? If the statement above is correct, am I going to experience a high current even if I disconnected the negative cable for 1 hour? So complicated with cars with computer system...
Q3. If you leave a multimeter connected for 20 minutes or so, wouldn't it damage the meter?
Q4. Found something interesting. This guy at youtube.com is using other method (by connecting 1 ohmn 10 watt resistor and checking DC volt consumption) to find the battery drain problem. Is this method right?

Thanks.
 

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Mercedes Benz C230, 1999
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1 Posts
C230 Battery: Group 49 vs Group 93

Needed a new battery and went to NTB.
They didn't have a Group 49, but said a Group 93 would be "equivalent."
Put it in. Power windows won't work! (or will work very slowly, with many button pushes).
Returned battery to NTB and went to MB dealer, who put in correct Group 49 battery -- everything works. It was more expensive, but the other failed to work.
 

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CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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NTB = NoThing but Bad - I won't ever deal with them. Besides just plain bad customer service, they don;t properly torque lug bolts and end up breaking them or rounding them off.
 

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2002 C240
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Glad to see your car is back on the road and you are able to use one-touch feature for the windows.

For some parts, I don't mind paying premium to get MB part. Battery is one of those items.
Original batteries on these cars last 9 to 10 years without any problems (unless you drain the battery completely by leaving a light on).
Concur. My 2002 C240 with 117K has original battery in it. Never had to charge it, but I know I will have to change it out soon.
 
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