SLcharger

My service battery, located in the trunk, within a few day has passed away, giving up spirit. It started about a month ago. When the car was in garage fore more than a few day“s, the battery was partly discharged, so that the car refused to turn on seat heating untill after a few miles, after the generator had a chance to charge the battery. The problem escalated until the battery collapsed. I did messure the current drawn from the battery, with car in parked mode, and just after turning off the ignition, the draw was about 5 amps. After a few minutes the cunsumption fell back to 1 amp. and then dropped to 0.08 amp“s steadily after about 30 min.
Those batteries are GEL pack batteries, designed for deep cycle mode, but obviusly they dont last for ever. My battery made 2 years.

At MB they say that it is known problem with SL“s not driven frequently, because the even low consumption of 0.08 amp“s does discharge the batteri over time. If there is a tracking device fitted, the problem is even worse.

Their advise is to drive the car regurlary, best at least every second day to maintain the battari fully charged.

Any one out there had the same problem ?

azferrari

The battery in the trunk (for electrical accessories) will be the first one to
discharge.......before the battery in your engine compartment, that starts the car. I only drive my car on weekends, so I keep a "battery tender" hooked up to the battery in the trunk to keep it fully charged.

Jeff
'03 SL500
'95 F355

uk1

I think this is what's happening to my 03 SL500. With only 8k miles it is constantly giving up and setting the car alarm off which I don't think can be disabled.

I tried fitting a "battery tender" to the front battery on as I reasoned it would trickle through to the rear but it showed the connection as being reverse polarity - so I lost my confidence and disconnected it!

Jeff

blueSL

Matches my experience exactly. I replaced the trunk battery after 2 years but I had let it go completely flat on a couple of occasions. It isn't hugely expensive but it's clear that if you leave your car for more than a week without driving it, you need to put it on a trickle charger to keep the battery topped up.

mdvijay

i think the best thing to do if you are not using the sl as a daily driver ... install a battery trickle charger( preferrably use mercedes product) to the battery in the trunk that way the battery stays charged and never gets completely discharged that way you can prevent the damage to the battery...it will last longer... i have 2003 SL55 and it is in storage (this is the third winter)i have trickle charger in place ...buy a good quality trickle charger there are different kinds available...get the one mb has...mb has recently upgraded their trickle charger
good luck
Warm Wishes for the HOLIDAY SEASON/and HAPPY NEW YEAR
Vijay

blueSL

I've installed a socket in my trunk so that when the car is in the garage, I can reach up, grab a auto-rewinding cable from the ceiling and plug it in. Worth looking at chargers made by Mascot - www.mascot.com - they charge the battery in three stages, the last of which is a trickle charge which can be left connected indefinitely. I'd say there's no particular reason to buy a Mercedes part - they are just buying it in from somewhere else and adding their markup.

uk1

I'm going to replace the rear battery.

Is there any special procedure for changing it - or is it a simple disconnect/reconnect?

Thanks.

blueSL

No special procedure, very straightforward.

SLcharger

Blue SL, UK1.

That is not totally true: After installing and reconnecting the new batteri, you must set the clock, reset the ESP, by turning the steering whell from full right to full left ( you will se the ESP notice go away in the info display ), and vind down and up the windows, all done with ignition on. This must be done to proper reset the systems.

When that is done, everything will be ok again.

Merry Christmas :p :p :p

uk1

Thanks for the feedback.

I don't know about you guys - but it seems Mercedes are doing the best they can to get you to go back to them for the battery. I cannot see anywhere in the manual what battery the service battery is. If I look at the battery it says

" Varta A230 541 0201 12V 70 AH 760A EN"

If I go to the Varta site it doesn't have the new SL's listed - and every other car battery site also doesn't say what it is.

Anyone know what it is please?

Also - do you need to put a password into COMAND to get it going again?

Any pointers greatly appreciated.

SLcharger

You need no password, just hit it.

If you want to fit a no MB battery. take it out off the car and bring it to the dealer. Things as physical size, tabs for fitting, ventholes, size of poles, etc. are important. If they dont have the battery in their listings, remember to tell them that it is a GEL battery. This is important regarding service life ( deep cycle battery ).

Now aday“s it is quite common that car manufacturer do a deal with supplyers, where the vendor is forced to accept that only the car manufacturer can sell and distibute the products. It is not very sympathetic, but it is a way to keep buissenes going.

In my opinion the few bucks saved by trying to get a battery from an unauthurised dealer is not worth the effort.

Merry Christmas

uk1

Thanks for your reply, and you'll find this strange.

It's not that I want to save money. I bought the SL after all (!)

I simply hate the MB dealerships and cannot stand the whole concept of making a drama out of a simple thing mentality they seem to have.

The other thing is this. The back battery needs to be a different type of battery than the one MB fits. There is a class of battery that deals better with abuse than standard batteries. Clearly this one isn't one of those. I'd love to find one that takes full discharge and charge with less complaint.

Also, why when I connect the battery to an intelligent charge with the correct polarity does it show it as reverse polarity. Is it anything to do with the two batteries being connected?

It's strange.

Jeff

SLcharger

Hi Jeff

I respect your opinion, although i dont share it. If you want the top of the line battery, that will take heavely abuse, then you must go for a AGM battery (absorbed glas mat ). These batteries originally developed for aircrafts and spaceships, are now avalible on the marked. They are commonly used in the boating industry now a day“s, since sailboats have the problem to use a lot of power and only running the engine infrequently.

About your intelligent charger. If it doesn“t have a setting for GEL battery, it will not work, since one of the methods the charger uses to find out polarity and battery type is to messure the resistance through the battery, and resistance in a GEL battery is bigger, so the charger thinks something is wrong here. You will have to get a more simple tricle charger that will charge your battery without the hightech stuff. They cost around 25£.

The two battries in the car are totally seperated, and do not affect each other. A split device allowes the generator to charge both batteries at the same time, without letting them draw power from each other. By attatching a charger to the battery in the trunck, you will not charge the starter battery.

uk1

Thanks for your comments - very much appreciated. I'm going to follow up these batteries.

You say I need the intelligent charger. Do you mean to overcome the problem I have with the existing coriginal battery? That implies that the SL already has an AMG/GEL battery fitted as original as when I fit the lead correctly the reverse polarity lights up - but when I fit it icnorrectly it doesn't?

So to clarify - are you suggesting I need an intelligent charger - or cheap charger for the replacement battery only and that my Accumate trickle charger should be working correctly with the oroginal battery?

Also, doesn't the idea of AMG/GEL defeat the need for charging as once charged they retain it?

Many thanks,

Jeff

blueSL

I've been through all of this, which is why I now have my socket in the boot.

It's correct that you have to reset the windows and ESP - but I've been used to doing that when the battery goes flat. In the UK, the clock sets itself automatically when you switch on the radio.

Rather than mess about with part numbers, it's much better to get it from your Mercedes dealer. I took the old one back for them to dispose of and paid £150 for the replacement - noise level - and replaced it myself. When they asked me if I wanted them to fit, I told them to stop being ridiculous.

An "Intelligent Charger" is one which measures the battery discharge state before/while charging it so that it is charged optimally. This is normally a three stage process - charge at constant current until the battery is 80% charged, charge at higher constant voltage which forces additional charge in the battery to fully charge it and then trickle charge at nominal constant voltage indefinitely.

As I said before, the chargers to use in the UK are made by a Norwegian company, Mascot. Check out www.mascot.com; if you are mainly looking for a trickle charger, the Model 9640 is ideal, about £30. If you want to be able to charge a flat battery quickly, the 9740 and 9840 are what you need, about £100 - £200. These chargers are a million miles from what you'd pick up at a car accessories store and I have one of them in each of the bays in my garage to charge each of the cars using recoiling cables reels mounted on the ceiling.

In the UK, obtain from rswww.com or www.cpc.co.uk.

SLcharger

Jeff

Am i missing something here ?

I got the impression that you had an intelligent charger, as you wrote:
Also, why when I connect the battery to an intelligent charge with the correct polarity does it show it as reverse polarity. Is it anything to do with the two batteries being connected?

The battery fitted in your car schould be a GEL battery, that is what MB fits originally. The charger that Bluesl recomends "the Model 9640 is ideal, about £30 " is an okay device, it will do the job. Remember the battery schould be connected to the charger all time when the car is in the garage. This charger will cope as well with an AGM battery. The low charge current of the charger dosn“t matter since it is connected all the time you dont use the car, and therefore have all the time in the world to bring up the battery to a 100% again.

No battery in the world can retain its charge when current is drawn from it, and at the same time, no charging is done. You will have to charge it, one way or the other, drive the car, or charge it with a remote charger, thats about it.

ClayJ

Nicely done, SLcharger.

SLcharger

ClayJ

Thank“s

ClayJ

Sometimes it's just some general information. Sometimes it's to share something that I've found or know. Sometimes it's just to laugh at the stupidity. But I really like going to the forum when I see intelligent, well put, helpful discourse -- and I always try to reward positive behaviour......
and again, Nicely Done.

SLcharger

You seem to be a man with quite a calibre. Thanks again

uk1

Thanks - the information that was missing when I posted my question was that I didn't know that the original battery was a GEL battery, only that you were suggesting that the replacement should be one.

I've now found the Varta battery that replaces it and I plan to connect it to a CTEK charger.

Thanks for the help.

Jeff

uk1

For completeness and to inform others with the same problem now or in the future.

The original fit Varta batteries (not certain about non-uk markets) were announced to be sold by Varta to the after-sales market in October 2005. They will only be selling two sizes initially. These are the two MB batteries:

VARTA ULTRA dynamic

Here are the various part numbers available in this range.
Please click on the individual battery part number for more detailed technical information.


Article number Voltage [V] Battery Capacity [Ah] Cold cranking current, EN [A]
570 901 076 3332 12 70 760
595 901 085 3332 12 95 850

So the two batteries they are offering in this range appear to be the front and rear batteries for the SL. However, although they are on the Varta web site, at the moment distributors in the UK haven't heard of them or stock them.

In the interim I connected a CTEK XS 3600 to the battery and at the moment it appears to have done the trick in that the battery has now been charged and the SL doesn't show all the errors it use to when I start.

Perhaps the battery is a bit more forgiving and as long as I keep it on the CTEK when in the garage then I might not need to replace the rear battery as urgently as I thought.

Hope this helps others who find themesleves in the same situation.

Thanks again to those that patiently offered advice.

Jeff

dyllanc

Hey guys, just bought the battery tender... quick question:

1) How did you guys hook up Battery Tender Plus to your trunk battery?
2) Did you guys use the ring terminal harness or the aligator clips?
3) Also, do you guys close the trunk with the battery tender cables hanging out or do you leave the trunk open? If you leave it open, what do you guys do about the trunk light?

Any help appreciated....! My SL500 is a garage queen during the week! heehe

SLcharger

Use the ring terminal, it is the safest connection. Leave the trunk open, you will experience that the car notice the open trunk, and after a while, turn off the light.

Love to get some feedback later.

good luck.

uk1

I didn't know the light went off by iteself so I tried closing the trunk using other dummy wire first and there was safe movement ie no danger of the trunk lid cutting the cable. So I close the lid.

My charger appears to have done the trick. It seems to me, that if this were the front starter battery I'd need to change it with a clear sense of urgency. But as it's the rear battery and the charger is now left permanently connected I cannot think of a reason to change the battery before it's next normal service.

Jeff

......... edited: PS I found a new little socket in the boot. 12 volts I guess - but what for?