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SL550
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Discussion Starter #1
The dealer salesman was singing the praises of having two
batteries in the 2004 SL500. Has this been a feature of
SLs for some time? Or is the second battery needed to
support operation of the roof from the remote when the
engine is not running?
 

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'00 ML320 Elegance
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The dealer salesman was singing the praises of having two
batteries in the 2004 SL500. Has this been a feature of
SLs for some time? Or is the second battery needed to
support operation of the roof from the remote when the
engine is not running?
Hmm, the W211 E-class also has a smaller auxilary battery. I suspect that it is for powering certain accessories so as to take the load off the main battery.

I'm not sure if the smaller battery has enough power to support the roof hydraulics. I'll have to ask!
 

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2004 SL55 AMG
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One is dedicated to cranking the engine and providint the engine managment computer with power. The second one is for accesories. It can run off just one battery but you might have problems running some accesories.
 

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SL55
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If you had only one battery, I'm under the impression that if you were to sit for a long time (without the engine running to keep the battery charged) while listening to the radio and you raised the top up and down a few times you might find yourself stranded (unable to start the car). This might not happen until the battery loses some of its capacity with age and use.

With two batteries, I'll bet that one of the batteries (probably the one in the engine compartment) is NOT used by all the power hungry accessories and is reserved for starting. So, you should always have plenty of battery juice to start the car regardless of how long you have enjoyed the radio and other accessories with the engine not running.

It is common with boats to have two batteries for this purpose also (i.e. so you can use your accessories with the engine off and not have to worry about whether you will need a Coast Guard rescue).

Viper2
 

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'05 330i ZHP
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I read a similar article in the C&D a while back, and I dont understand why M-B dosnt start building cars with the new batteries. Seeing that their quality is down right now, that'd be a perfect move to improve their stance on BMW and Lexus.
 

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C 111 Nardo
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Many things will need to be designed (and are being designed) with the new voltage in mind

It can't be done very quickly.

In addition, the 42V batteries will cost a bunch more than current techonology, and since MB is movng away from shifting better engineering costs to the customers, that's not within the current company lines, but they will have to, and cheaper solutions to built 42V batteries will emerge.

In addition, at present, the lifespan of the 12V batteries is long and customers who would expect a 42V battery given current constraints would be most disappointed because the 42V do not last as long. Do you really need another reason to be stranded on the side of the road in your new MB?
 

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Failed attempt at a dual voltage approach...

EETimes (2002)
DaimlerChrysler, meanwhile, has announced that it will also employ a dual-voltage design on a future Mercedes SL.
Search on ISO 21848

Project details
Document: ISO/DIS 21848
Title: Road vehicles -- Electrical and electronic equipment for 42 V networks -- Electrical loads
Edition: 1
Number of pages: 13
ICS: 43.040.10
Stage: 40.20
Stage date: 2004-02-09
Target date: <b>2004-03-31</b>

With a clear standard in existence, manufacturers will be less hesitant to move on...
 

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SL 500 2003 former; E350 2007 former, C320 2005 Actual.
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A friend of my told me that form MB headquarters tell him that the two bateires is because if thw owner left some accesories on or for any reasone the batery dry out you still can contact tele aid beecause the other batery let you star the car or run some of the emergency accesories ( my frend has a ML320 2002 and his wife let the light on and he has to use his celular phone to cantact MB for them to send roadside asistance) with the two batery that did not happend again
 

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I ask the shop foreman this guestion long time ago. He said the second battery is a small one, and it's a back up to start your engine in case your main battery die on you. Not for any accessaries. The second battery will never be drained, because it is connected to accessaries. Please stop making up wierd reasons!
 

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2003 SL500
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the smaller battery under the hood is 35 amp hours I believe. The big battery in the trunk does not participate in the starting of the vehicle, AFAIK..

Greg
 

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2003 SL500
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the smaller battery under the hood is 35 amp hours I believe. The big battery in the trunk does not participate in the starting of the vehicle, AFAIK..

Greg
 

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SL65
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The second battery is for the consumer electronics- such as radio, roof operation. I sell these cars- and we often have one on our showroom- and from people playing with the trunk access button- to operating the roof and radio, etc- it will kill the battery. The main battery is used for all electronics related to engine operation and performance- the second is for consumer elctronics. And you will know when it's dead- via a message on the on board display- it will read "consumer electrioncs offline" to fix this (if it's not too bad) is to drive the car about 8 to 10 miles- the alternator will regarge the battery and you are back in business. I have had to do it a few times becasue of customers (mainly sales people showing the customers) neat features that the car has-anyhow- as to why they do this- there isn't just one answer- and all the reasons that i have seen listed in the posts before me are all correct. Hope this helps- if you have any questions feel free to email me!

-Dallas
 
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