Is it another defective MB Battery or has the CTEK CT 5 decided to malfunction?

Submariner1

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some may remember the mare I had with my recent new CL Battery .... basically it passed the Mobilo attery test on 4 call outs, and then thankfully refused to start on the 4th call out and failed the test ... shorting cells or something!

So MB replaced it.

Pretty much the same crap on this battery, wont hold a charge. Charge it fully, and the next day its at 12.6V .... which over the last 4 months has dropped to 12.4V.

The ususal charge cycle:-
Charge it for 10 hours till the CTEK went into “care mode”, and the Battery is at 13.1V leave it 2 days and its was at 12.5V :(
Note in this, what I call a full charge cycle, the CTEK would output up to 14.9V and 3.59A until fully charged, then drop down to 13.1V in care mode with say 700mA current.

Recently since my op. The car was not driven for 20 days. And the battery was at 12.2V. To be expected. Moving her in the driveway .. so 3 starts . She started fine.

Put her on charge ... expecting at least 8 to 10 hours to get her fully charged .
Oddly I noticed after about 1 hour she was staying at about 12.9V ... and 3.2A , by then she would normally be at 14.6V to 14.9V. And rise to 3.59A ( the Cteks max.).

Then blow me in 4 hours I noticed she was in “Care Mode” at 12.8V and 870mA! Not the normal 13.1V.
So left for 4 more hours and disconnected ... next day she was only at 12.2V!

I tried the CTEK on the wifes A Class battery, ok its only a 70AH battery not 95AH, that was at 12.6V and within 30 mins it was pumping out 14.2 V. As I expected the Ctek woukd behave.

To me this all spells its another of these dam defective MB batteries. But could it be the Ctek?

To my mind, if the CTEK works as it should on the A Class battery; but does not produce more than 13.1V on the CL it smacks of something like a high or low resistance in the CL Battery tricking the CTek into thinking its fully charged, and thus making it go into Care Mode; or this naff battery just wont take more than 12.9V.

Any ideas?

Note the CL Alternator produced 14.3V at tickoover, or 14.9V at the start of a short journey as it should.
This battery has been tested 3 times by Mobilo and once by the main dealer .. passed every time.
Last month the battery reg. was also tested by the dealer, when ot was in for the wheel sensors at no charge.
They confirmed the battery drain fluctuated between a few short peaks of 40mA and 2 mA. All within spec as they say my CLs config. Could happily be up to 60 to 65mA
So no battery drsin issues imo.
Mobilo also tested the drain and once shut down found 20mA.

So before I go balistic on Mercedes, do you think it could be the Ctek charger?

I guess you can feel from the tone of the post, I think its effing disgraceful, Mercedes refuse to change a battery without you paying for it to be tested .... where the test costs more than the battery! To me thats no warranty at all.

Or should I just leave her until, she fails to start and call out Mobilo, until “they” realise its costing them a dam site more in call outs than the cost of 3 batteries?

TBH I am a tad surprised she started 3 times at only 12.2Vs.
Note so far she always manages to start ... so does it matter!
 
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LostKiwi

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Are you actually experiencing any problems or is this just micromanaging your car?
 

flowrider

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Unless the battery fails i would just leave it. You might be worrying about nothing.
 

Botus

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I think you worry over nothing

I replaced my rear battery about 3.5 years ago (the monster AGM 22kg thingy with a 5 year guarantee). Since then nothing plays up, but the numbers you get aren't as high as "you" expect to see.

two weeks ago I drove two 70 mile trips, then did a longish drive last weekend. My new 2019 mapping turned up (with actual maps dated Nov 2017 !!!), so put the vehicle on charge overnight (expecting the battery to already be at a fairly high state of charge) as I connected it, it said it was at 12v !!! (over the last 3 years its always been around 12.6v.... as to connect it up you have to have woken up the car to get to the battery). Put on charge at 3.47 amps and 4 hours later was going to disconnect and go to bed when I saw it was (as usual) still drinking up electricity at full rate with low 12v showing.... this time with the car fully asleep!

As the boot seal is massive you can easily close the boot fully with a thick mains cable not even showing a mark where the boot closed ! So I left over night to carry on charging.

18 hours later unlocked the car to see the charger had switched to maintenance mode... with the message battery health High and 12.6v

Put the key in ignition to position 1 this wakes up command and phone system, went back and switched the charger to on (which it happily accepts) as current draw now high..... Put in the new map disc and said go. Kept an eye on voltage throughout as command can switch off and stop maps loading. With charger assistance it was maintaining 12.3v

Maps loaded fine in 42 minutes, all working, battery left to top up after key turned off.... saw it climb to 12.7v with ignition off rising to a max of 12.9v when it tripped back to maintenance mode

you may want 14v, maybe it should but mine never has.....


By the way the rejuvenated original (at 12 years old) is still going strong 3 years after adding 40ml of distilled water to each cell. Having not touched it for 6 months after using heavily as feed for a halogen work lamp, I put in on charge (using a lidl special) to find it was at 12.6 v !!! left the charger on and forgot about it..... two weeks later, I saw it was in maintenance mode with 14.1v showing. Something it, nor its replacement ever managed when connected to the car !!!! Having fixed it and seeing how the car treats the new one, I wish I'd kept it in the car and saved 150 quid
 
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Submariner1

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I think you worry over nothing

I replaced my rear battery about 3.5 years ago (the monster AGM 22kg thingy with a 5 year guarantee). Since then nothing plays up, but the numbers you get aren't as high as "you" expect to see.

two weeks ago I drove two 70 mile trips, then did a longish drive last weekend. My new 2019 mapping turned up (with actual maps dated Nov 2017 !!!), so put the vehicle on charge overnight (expecting the battery to already be at a fairly high state of charge) as I connected it, it said it was at 12v !!! (over the last 3 years its always been around 12.6v.... as to connect it up you have to have woken up the car to get to the battery). Put on charge at 3.47 amps and 4 hours later was going to disconnect and go to bed when I saw it was (as usual) still drinking up electricity at full rate with low 12v showing.... this time with the car fully asleep!

As the boot seal is massive you can easily close the boot fully with a thick mains cable not even showing a mark where the boot closed ! So I left over night to carry on charging.

18 hours later unlocked the car to see the charger had switched to maintenance mode... with the message battery health High and 12.6v

Put the key in ignition to position 1 this wakes up command and phone system, went back and switched the charger to on (which it happily accepts) as current draw now high..... Put in the new map disc and said go. Kept an eye on voltage throughout as command can switch off and stop maps loading. With charger assistance it was maintaining 12.3v

Maps loaded fine in 42 minutes, all working, battery left to top up after key turned off.... saw it climb to 12.7v with ignition off rising to a max of 12.9v when it tripped back to maintenance mode

you may want 14v, maybe it should but mine never has.....


By the way the rejuvenated original (at 12 years old) is still going strong 3 years after adding 40ml of distilled water to each cell. Having not touched it for 6 months after using heavily as feed for a halogen work lamp, I put in on charge (using a lidl special) to find it was at 12.6 v !!! left the charger on and forgot about it..... two weeks later, I saw it was in maintenance mode with 14.1v showing. Something it, nor its replacement ever managed when connected to the car !!!! Having fixed it and seeing how the car treats the new one, I wish I'd kept it in the car and saved 150 quid

Thanks for the useful info.
After an 8 hour charge yesterday of which 4 hours were in Care Mode (alledgedly fully charged) .

I took it off charge, and checked today to see, that it was only at 12.4V ( note the 7 year old one would have been at 12.5V or 12.6V dependant on recent journeys).

14.47pm @ 12.4V with drain 600mA all shut off , left 9 mins to shutdown fully .
@ 14.56pm @ 12.4V with a drain of 40 mA all shut down.

15.00pm Started charging at 12.7V @ 3.32A. 2 mins later rose to 13.0V

15.05pm i.e. after 5 mins, rose to 13.2V @ 3.26 A

16.38pm found it was now in Care Mode! charging at 13.0V @ 1.03A
(Oddly only took 1 hr 38 mins to get to full charge! ... normally that would take 6 + hours, and at 14.8V and 3.59A)

17.52pm still in Care Mode! charging at 13.0V @ 1.01A

Completely confused ... and like you, I wish I had left the old one in until it died!

All my SL 500s were normally at 12.6 to 12.7V whenever checked .

Maybe its so ething to do with the later one-battery modification, or the fact they downgraded the battery from 95AH to 90AHs.

Or as I suspect Varta have a big batch problem!
Masked by MB’s evil policy.
 

KennyN

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All my SL 500s were normally at 12.6 to 12.7V whenever checked .

Maybe its so ething to do with the later one-battery modification, or the fact they downgraded the battery from 95AH to 90AHs.

Or as I suspect Varta have a big batch problem!
Masked by MB’s evil policy.

When was the last time your multimeter was calibrated , your test results are listed to 0.1v so if your meter is slightly out / slightly out of battery or you are testing at various ambient temps then it could be throwing you a curve ball.

All our techs have decent £300+ Fluke multimeters and we get them calibrated every year to keep all our electrical / electronic checks consistent.

Kenny
 
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Submariner1

Submariner1

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Are you actually experiencing any problems or is this just micromanaging your car?

Only other current issue is the rear headrests wont go down.
No messages and no fault codes.

Ref the replaced faulty battery ... when that got low I had a hist of spurious issues.
Malcolm did write to me and said iho , these big Mercs like to see a minimum of 12.6Vs

As I really rated his knowledge, I would have liked to sort this low voltage issue before spending bucks sorting the headrest issue.

Not able to drive after the back op, so I might disconnect the battery tomorrow if I feel up to it. And see if that resets the vac pump.
I would assume if that was causing a problem I would have a drain bigger than 40mA to 2mAs, and I would expect to see a few fault codes on the MBV2.

I also dont like the “change”. Namely previously this battery would suck 14.8V and 3.59A ( as per the CT5s spec sheet), for up to 10 hours to charge it from say 12.3V to care mode.
And can now take it from 12.2V to Care mode in under 4 hours at a max. Of 13.0V and 3.26As.
To me thats illogical.
Or today the CT5 took it from 12.4V to care mode in 1 hour and 37 mins. Pushing out only 13V and 3.26A tailing down to 1.1A

Note voltages were checke with a new Fluke meter and double checked with the old Multimeter and they are consistent to within 0.1V.

OK the low drain figure of 40mA to 2mA could mask a huge intermittant drain. But my logic says were that the case. I doubt it would start (and it did stsrt 3 times in succession moving it in the driveway) after being left standing for 23 days!
 
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Submariner1

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When was the last time your multimeter was calibrated , your test results are listed to 0.1v so if your meter is slightly out / slightly out of battery or you are testing at various ambient temps then it could be throwing you a curve ball.

All our techs have decent £300+ Fluke multimeters and we get them calibrated every year to keep all our electrical / electronic checks consistent.

Kenny
The Fluke is 4 months old and within 0.1V of the old multimeter.
Another test is I have to flick off ( via a quick release cut off switch) the DRLs during charging, because at 13.1V they come on. Tested by putting these on when it said 13.0V and they didnt light.
Previously as soon as the charger went into Charge mode they always lit!
 
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Submariner1

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What are the chances of yet another faulty battery?
I would have thought/hoped ... zero.
But as the Mobilo tech said 10 years ago I never saw a defective new battery. But in the last year or so I have seen quite a few!

The production date of this replacement was the same month of the first defective and replaced unit.
Hmmm same batch?

Maybe I am sensitive, because 4 years ago we had the same thing with the A Class battery, over £900 of diagnostics and battery tests and Satelitte Tracking device removal costs.
Only to be told no fault with the car or the battery!
Then on the 14th Breakdown I said f@ck it, just put in the biggest battery you can in that car.
And guess what I has worked perfectly every day since!
So imo these battery tests are worth utter b@llocks!
The dealer did refund £486 of testing fees! And repaid me for the new battery.

And note this first new battery did pass the battery test 4 times within a week, and passed it again the day
They replaced it.
Luckily when they told me it had passed and was fine ... I said OK show me it start the car.
A big red face when it couldnt! They even had to apply power to get it to a state the battery test would run!
 

d215yq

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Could it not just be multimeter error?

My alternator failed and replaced with a new alternator and voltage regulator and when idling it was 12.4V and when revved it went up to 12.8V. Now that made me a bit worried because in theory it needs a lot more than that to even charge the battery but since in real life it somehow managed to charge the battery in 20 minutes and then when i later left the car sat for two weeks it still started perfectly I just assume that the multimeter is wrong and the new alternator actually works...even if the alternator is right I don't really care if it somehow does manage to charge the battery anyway for whatever reason...

That was all 3 months ago and had no qualms taking it on a recent 1500 mile trip around the South of Spain no prpoblems and it still has a 4.5 year old battery which was flattened twice by my broken alternator. I suppose I should keep a spreadsheet of daily (possibly erroneous) readings on that but i won't bother because a) if it does actually fail I can get a new one delivered to wherever I am within 2hours for 80 Euro and it would take me less time to wait for that and fit it then mess around with taking readings everyday and b) because all the opening doors/courtesy lights/locking and unlocking it and taking readings would all cause a drain and make it more likely to fail.
 

alexanderfoti

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You cannot measure the voltage accurately with it connected to the car.

Take the battery out, fully charge it, remove the surface charge, then check the voltage after 3 weeks. You will find its fine, im sure.

12.4v is fine with it being connected to the car.
 
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Submariner1

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Great Service from CTEK ...
They are replacing the Charger .. it should go up to 14.8 V

I didn't realise it had a 5 year guarantee! :):)

At least this will take the charger out of the equation ref the erratic charging cycle.
 
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Submariner1

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Could it not just be multimeter error?

My alternator failed and replaced with a new alternator and voltage regulator and when idling it was 12.4V and when revved it went up to 12.8V. Now that made me a bit worried because in theory it needs a lot more than that to even charge the battery but since in real life it somehow managed to charge the battery in 20 minutes and then when i later left the car sat for two weeks it still started perfectly I just assume that the multimeter is wrong and the new alternator actually works...even if the alternator is right I don't really care if it somehow does manage to charge the battery anyway for whatever reason...

That was all 3 months ago and had no qualms taking it on a recent 1500 mile trip around the South of Spain no prpoblems and it still has a 4.5 year old battery which was flattened twice by my broken alternator. I suppose I should keep a spreadsheet of daily (possibly erroneous) readings on that but i won't bother because a) if it does actually fail I can get a new one delivered to wherever I am within 2hours for 80 Euro and it would take me less time to wait for that and fit it then mess around with taking readings everyday and b) because all the opening doors/courtesy lights/locking and unlocking it and taking readings would all cause a drain and make it more likely to fail.
Nope, checked with a new Fluke and the old multimeter.
And doesnt explain how it goes into care mode sometimes in 3 hours and normally in 10 hours.
Either the CTEK is faulty or its reading unusual resistances from the battery.
 

Botus

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don't connect to BOTH battery terminals

one to + on the battery and the other to an earth on the vehicle
 

Botus

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I think I have found a fix for your car....

start the car drive 20 miles, park it up, two weeks later drive for 20 miles park it up.

if you follow this routine or drive more frequently over longer distances I don't think you will need to think about the battery for another 10 years
 

davidsl500

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I think I have found a fix for your car....

start the car drive 20 miles, park it up, two weeks later drive for 20 miles park it up.

if you follow this routine or drive more frequently over longer distances I don't think you will need to think about the battery for another 10 years


At the end of the year he will be 520 miles from home !:)
 

L John

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don't connect to BOTH battery terminals

one to + on the battery and the other to an earth on the vehicle

I always connect to the earth bolt because it's an easy connection but direct to the battery is as good if not better because it's the battery that he is charging, so a direct connection can't be worse than charging through the negative cable from an earth point.
I think you might be thinking of jump starting which is when the negative should be connected to the earth of the vehicle to get the path of least resistance.
 

Botus

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allegedly ...if the car is pulling current out of the battery, by connecting ones charger not to the battery post, the charger gets a better reading of what's going on
 

L John

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When no current is flowing, both ends of the wire are at the same potential (voltage).
When current flows through a wire it has a voltage drop caused by the wires resistance, connections also cause resistance.
I'm not convinced a direct connection for charging is any worse than the earth pin.
If there's a poor connection at a battery terminal or earth pin due to corrosion, the charger would work best when connected directly to the battery.
The connection would need to be rectified but direct connection would ensure the charger is not blamed if the body contact was poor for any reason
I'm happy to be told I'm wrong if the charger does read the battery charge state and any vehicle sapping losses better from a point further away.
 


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