R230 Dual Battery On-board Electrical System

[SL63 Mark]

I’ve never tried switching it on and off again, Sounds like a good thing if you can clear the consumers message by switching the ignition on and off, maybe the battery is borderline charged. I’ll have a go sometime, my car is the same year as yours.

If you were interested in what is happening, you could start by putting a meter on the battery before and after, and get some readings. Maybe it’s charging off the other battery.

 

[LostKiwi]

It may be the threshold for turning on the warning is 12.0v and the threshold for turning off is 12.2v. If the battery is 12.1v it will see that as above the threshold when turned on so not display message. I've seen this behaviour on our 230 a couple of times after a short run following a long period of non use.
I strongly suspect you'll need to get a voltmeter onto it to see what's happening.

 

[Oldcodger]

This is peculiar.

I went to do the checking amperage thing and measured the voltage across the terminals first with the -ve off = 11.5V

Connected the ammeter in line and this showed 2.2A but this with the boot bulb on (couldn't get it to switch off). Ok mental note made

I'd already decided that the cheap Chinese quick release terminal clamps fitted by a previous owner were going to go as they were in a bad state. In fact the negative terminal had signs of heat melting the plastic cover/handle and the +ve fell apart when I removed it!

I got some better quality quick release terminals off ebay and they looked a lot stronger with cast metal instead of thin plate.

Bit of a faff to get the +ve terminals connected as it has two cables thickness to clamp. Fitted a slightly longer bolt than supplied and tightened down firmly. Connected the -ve

Turned the motor on and right away no messages!

I have left it for an hour and tried again and still OK

Will monitor tomorrow but was it the crap terminals having some impact all along?

 

[LostKiwi]

Entirely possible that was the issue especially if the positive one fell apart.

 

[SL63 Mark]

Forgot to mention I always disconnect the boot light when testing for current drain. Just pull it out and disconnect. Easy to do, otherwise it stays on as you discovered. Your 2.2 amps at rest dosn’t sound too bad, as the boot light draws about that from memory.

Hopefully you have sorted the problem by replacing the damaged terminals. 11.5v sounds a bit on the low side, so see how it goes after a good run and a charge.

 

[bigtammc]

Can anybody recommend a quality trickle charger for the auxiliary battery ? I think my battery is on the way out and when I purchase a new one I would like to give it the best chance. This one is probably only two years old so not happy ! Overnight on a proper charger and its still charging at 5 amps in the morning. Any thoughts folks ?

cheers

Ian

Hi,I have a similar battery drain on mine too.have paid people to find the problem but no luck yet Mercedes prices too high. So after buying a new rear battery, the problem was still there. So I just bought a trickle charger on e boat for a tenner and it works fine.Now I think it's an electric car, because when I get home I put it in.....

 

[LostKiwi]

Hi,I have a similar battery drain on mine too.have paid people to find the problem but no luck yet Mercedes prices too high. So after buying a new rear battery, the problem was still there. So I just bought a trickle charger on e boat for a tenner and it works fine.Now I think it's an electric car, because when I get home I put it in.....

Try this.
Turn off Comand, then turn off car.
Leave the car a couple of days and see if the battery goes flat (probably a good idea to have the batter charger connected but powered off).
If it does start up the car (or charge the battery again). Once fully charged and no consumer message turn off (or disconnect charger). Leave a couple of days. If battery doesn't go flat the issue is Comand. If it does then it's something else.
This is how I discovered our Comand was the cause of our drain.

If we don't use Comand our consumer battery is fine for over a week. If we do it drains over 2 days until the battery is flat enough to shutdown Comand totally.

 

[Mike Mil]

Hi
a really interesting and useful post
I have just bought a SL R230 350 2003 and although from the receipts it has had a new consumer rear battery, in a mourning it comes up with a low battery warning with functions not available - this soon corrects after a mile or so - any suggestions as to the possible issue here
many thanks

 

[Big Janner]

Hi
a really interesting and useful post
I have just bought a SL R230 350 2003 and although from the receipts it has had a new consumer rear battery, in a mourning it comes up with a low battery warning with functions not available - this soon corrects after a mile or so - any suggestions as to the possible issue here
many thanks

Mike
My car is, like yours, a 2003 R230, but the 500.
I have the same issue . . . .stands unused for more that 2 or 3 days and when I come to use it, the low battery, functions not available message appears. Again, drive a mile or so and all is hunky dory.

I understand it is just all the electronics and electricals on board, slowly draining the battery
It's a common problem
After a lot of fretting and fiddling, I just use a smart charger now.
I connect it up about once a week and all is dandy

This is the one I use, cost about £25, there are others CTEK for example

https://www.maypoleltd.com/product/mp7423-4a-6-12v-electronic-smart-charger/

 

[John Laidlaw]

Mike
My car is, like yours, a 2003 R230, but the 500.
I have the same issue . . . .stands unused for more that 2 or 3 days and when I come to use it, the low battery, functions not available message appears. Again, drive a mile or so and all is hunky dory.

I understand it is just all the electronics and electricals on board, slowly draining the battery
It's a common problem
After a lot of fretting and fiddling, I just use a smart charger now.
I connect it up about once a week and all is dandy

This is the one I use, cost about £25, there are others CTEK for example

https://www.maypoleltd.com/product/mp7423-4a-6-12v-electronic-smart-charger/

I had a Lidl one which worked just fine, I'd connect mine every night but then I had the quick connect socket installed (by Malcolm bless his soul), and left the charger permanently connected in the garage, fed the wire and plug out reversed the car to the garage door- easy

 

[00slk]

I purchased a proper MB battery from Grangemouth MB and it stopped the problem on my SL, though not sure if it's still okay as haven't got the car at the moment It's away having ultimate care and attention

 

[Mike Mil]

Great thanks all some very helpful suggestions

 

[bully]

Like so many of you with an R230 I have the battery low voltage alarm come up after a few days on my 2006 SL350 which disappears after a few miles. Having been brought up to always disconnect the battery terminals on charging (doubly so with the R230 system!) are you guys disconnecting the rear aux battery when using a trickle charger? With talk of quick fit connections on the battery sounds like you're not. How safe is it to charge the aux batt without disconnecting and has anyone ever fried the electronics doing so?

 

[Oldcodger]

Like so many of you with an R230 I have the battery low voltage alarm come up after a few days on my 2006 SL350 which disappears after a few miles. Having been brought up to always disconnect the battery terminals on charging (doubly so with the R230 system!) are you guys disconnecting the rear aux battery when using a trickle charger? With talk of quick fit connections on the battery sounds like you're not. How safe is it to charge the aux batt without disconnecting and has anyone ever fried the electronics doing so?

Nothing has blown or set alight since I started doing that connecting to the service battery for a trickle charge

Make sure your charger is suitable for AGM battery which is what you should have in the boot.

 

[McDonald]

Like so many of you with an R230 I have the battery low voltage alarm come up after a few days on my 2006 SL350 which disappears after a few miles. Having been brought up to always disconnect the battery terminals on charging (doubly so with the R230 system!) are you guys disconnecting the rear aux battery when using a trickle charger? With talk of quick fit connections on the battery sounds like you're not. How safe is it to charge the aux batt without disconnecting and has anyone ever fried the electronics doing so?

I never disconnect the battery when using the C-tek. It works just fine with crocodile clips onto the terminals.

 

[LostKiwi]

Like so many of you with an R230 I have the battery low voltage alarm come up after a few days on my 2006 SL350 which disappears after a few miles. Having been brought up to always disconnect the battery terminals on charging (doubly so with the R230 system!) are you guys disconnecting the rear aux battery when using a trickle charger? With talk of quick fit connections on the battery sounds like you're not. How safe is it to charge the aux batt without disconnecting and has anyone ever fried the electronics doing so?

Mine has spent most of the past 2 years with a quick connect charger on it when not in use. No issues.
Before that Malcolm did the same for a number of years. No issues.

 

[John Laidlaw]

no need whatsoever to disconnect the battery whilst trickle charging, did it for 2 years without issue

 

[Painter16]

Think me consumer battery as had it,went to go out Friday couldn’t open doors had to use the key ,put charger on trickle ,but after 24 hours still no good so put on con mode if this don’t work ,time for new battery methinks ,not sure if it’s the original one if so ain’t done bad for 13 years

 

[Painter16]

So since last post above I put battery on condition mode and every thing fine , but if I don’t plug charger back in after using car ,even over night it drains down ,now this started to happen after a trip down to Cornwall September,filled boot with luggage for trip home ,nice day so took roof down ,only for it to stop about half way ,starting bleeping,heard a crunching noise ,roof went back up ok ,looked in boot the wife had put some cups she had brought as gifts up the corner on top off the cover and shut the boot ,so of course as roof opened it smashed cups and stoped, should have checked it meself ,anyway cleared it ,and tried roof again and all fine ,but about 3 days after getting back not driving the car battery drain down ,put on trickle charge did nowt , put on condition mode charges full ,but if left off overnight drains,could be original battery knackered or could it be something to do when roof hit the cups in boot , any ideas guys thanks

 

[Big Janner]

So since last post above I put battery on condition mode and every thing fine , but if I don’t plug charger back in after using car ,even over night it drains down ,now this started to happen after a trip down to Cornwall September,filled boot with luggage for trip home ,nice day so took roof down ,only for it to stop about half way ,starting bleeping,heard a crunching noise ,roof went back up ok ,looked in boot the wife had put some cups she had brought as gifts up the corner on top off the cover and shut the boot ,so of course as roof opened it smashed cups and stoped, should have checked it meself ,anyway cleared it ,and tried roof again and all fine ,but about 3 days after getting back not driving the car battery drain down ,put on trickle charge did nowt , put on condition mode charges full ,but if left off overnight drains,could be original battery knackered or could it be something to do when roof hit the cups in boot , any ideas guys thanks

New battery I guess