aeroman

So I have thought for awhile my car seemed a little off. Not as peppy and not pulling as hard. Went in for an oil change and Service A and they found the starter battery would not pass the medtronic test. (I knew it was getting weaker from a visit 6 months prior) Needless to say $196 bucks later for the battery off I went back to work. As always, getting on the freeway is usually a WOT run to 80 or 90 MPH. Way noticeably different. Put a grin on my face. I would normally not think a battery would affect but maybe with these big engines and all them plugs a tired battery does???

Thanks

aeroman

Not one thought huh? :P

aeroman

Word from the guys on the Porsche forum is yes a weak battery in cars like an SL65 will definitely impact performance.

TTtodd

It could be the ECU was reset or rebooted from the battery change.

aeroman

I asked about that happening mechanic said no.

dRockSL55

The adaptive throttle / transmission settings were probably reset someway as Todd suggested. A weak starter battery can't hinder engine operating performance, I'm not sure what the Porsche guys could be thinking?? even if the alternator was working overtime trying to charge it back up, you would never notice the effect on such a massively powerful engine... And there is still ample current left from the consumer battery and alternator for engine ignition coils.

aeroman

No. My Mercedes Master Mechanic has now checked even though he said it would take at least 30 minutes without battery power to reset. He also said that yes a weak starter battery can effect performance as the car uses the battery like a capacitor under high load spikes and then recharges it. He said many high performance vehicles are designed the same way.

BTW - the consumer battery and starter battery are on separate systems. If your starter battery is completely dead and the consumer battery is 100% charged you are not starting the car.

dRockSL55

The battery acts as a capacitor for reserve current (demand exceeding alternator/generator output) on any vehicle, this isn't a "high performance" attribute.

However, on an r230 the starter battery does not act as such. As you noted, we have two batteries. Except during emergency situations (weak or dead systems battery) they are separate and isolated from one another. The consumer/systems battery is the primary, supplying power to all vehicle systems (ecu and ignition included). The starter battery's sole purpose is to spin the stater motor. Changing it won't alter the engines performance other than if it will be able to crank over or not as it simply doesn't power anything else...

R230 battery system overview;
http://www.benzworld.org/forums/attachments/r230-sl-class/265471d1255206253-pdf-repository-r230s-dual-battery.pdf



There is some logic to what the Porsche guys told you. On some performance vehicles the alternator is clutched, its actually shut off on high throttle positions to reduce load and maximize engine output, running the car straight off battery and the alternator acting as an idler. Another method that is now more common on modern cars with Ecu regulated alternators is for the ecu to simply turn off the regualtor so the alternator drag is far reduced (although the engine is still spinning the mass unlike a clutched alt)
On cars like these there could be a potential performance difference for a weak battery vs a strong one as when the alternator is shutoff the ecu and more so the engine ignition coils are using the battery alone for current. However even in these cases it's the ecu that contrs the alternator, and will only do so with sufficient battery voltage which is monitored continuously.
The r230 sl65 doesn't use a clutched alternator, and again the starter battery wouldn't be the one supplying current here so once again there is performance change to be found through the starter battery.

BlownV8

Reminds me of the time I was having trouble with my Ferrari so I went to a Lamborghini forum for help...........

aeroman

Well if people around here helped as much as over there I could see your point. In this case though most of those guys have a myriad of cars and know a ton about them.

aeroman

That is not even from Mercedes and also from 2002. I need to confirm but I believe a lot of how the electrics function changed in 2005.

but if you are right and all I have to do is detach the starter battery for 2 minutes and reset the adaptive that is great.

BlownV8

Just meaning with you. I know you like Rennlist.

aeroman

What you saying I got a bad rap over here? I can't think of anything I have done that would bring that on.

BlownV8

Meant to say just messing with you. Damn auto correct.

dRockSL55

What do you mean that is not from Mercedes? That is an actual Mercedes tech service document, written to better explain the r230 dual battery system for Mercedes techs. It works exactly the same on a 2005. The r230 was launched for 2003 model year in the U.S. hence 2002 publishing

And I never said all you have to do is disconnect the starter battery for a couple minutes to reset the adaptive functions. What I did say is that your adaptive functions were most likely *somehow* reset during the battery swap which would best explain what you experienced. As I explained in detail a new starter battery simply would not alter engine performance, as it does not power anything besides the starter motor except in low battery operation (with dash warnings to go along)

I'm not sure what you want to hear? Sorry you don't find people 'here' helpful but on this topic people 'there' don't know what they're talking about

aeroman

hmmmm. Looks like powerpoint to me. I have a late year 2007 build SL65 not a 2005. I said lots of things changed after 2005.

I watched the battery swap. Nothing was done other than swapping out the battery so "somehow" didn't happen.

I think you took me wrong. I asked for input. I joked when I got none.

I think I will trust my AMG Certified mechanic. His opinion is that anything that is running "weak" on these cars will affect them.

I'm still thankful for all input.

BlownV8

What changed after 2005?

aeroman

I don't have a complete list but I have heard my mechanic and people on this board say that lots changed between 2005 and 2007.

BlownV8

Name some changes.

aeroman

Well one I know for sure is that intercooler pump is on the passenger side easily accessed. On my 2007 it is on the right side and you got to take the damn bumper off to get at it.