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Stop/Start battery question.

mikrt

Active Member
Joined
Dec 6, 2018
Messages
341
Location
Cardigan
Car
2013 C220 CDI BlueEFFICIENCY AMG Sport Plus 7G-Tronic Plus 4dr
So I've got my new iCarsoft plugged in, and as my stop/start eco has never gone green, I thought I'd check it out. (I am fully aware however, that if I do get it working I will probably be cursing it, but I'm a bit OCD and trying to get no faults!)

All perameters are met, except "On-board electrical system" showing "Not OK"

Car not started for a week, Battery voltage = 12.00V
Car running for 5 mins, Battery voltage = 14.7V
Stop engine & test, Battery voltage = 12.44v

Connected battery charger to small battery (original one?) in boot, showing 14.6V and so will not charge it.

Connected battery cherger to big battery (only 3 years old) under bonnet, showing 12.9v (and I've left it charging)

I'll leave it to fully charge and then try again, but the car does do monthly 300 mile drives each way up and down the M4 (and beyond) fortnightly and it stays amber when I'd expect battery to be fully charged so not sure it'll be any different.

Would a battery have any other issues not showing from these tests do you think?

Thanks.
 
Not necessarily.

How old is the main battery?

I recently replaced a 6 year old battery where the yellow ECO was going green but the replacement battery sees ECO green a lot more.
 
Hi John, I'm assuming the bigger battery is the main one, I stated above it was 3 years old, but after rechecking, it's actually 2018, so newer than I thought!
 
Hi John, I'm assuming the bigger battery is the main one, I stated above it was 3 years old, but after rechecking, it's actually 2018, so newer than I thought!
If you are certain that your main battery is only one year old, then suggest that you charge up the battery using a decent charger (at least overnight possibly longer if possible) and retest your ECO Start/Stop.

If after a full charge the ECO Start/Stop fails to kick in once all the conditions have been met, suggest you examine the age and condition of the Aux battery and replace if necessary.

You did not state the year of your car so difficult to pass further judgement on the issues reported.
 
Yes wongl, genuine merc/varta battery 03 18 on the negative post.
Car is 2013, I thought it was with my car details on left, sorry.
The smaller battery looks brand new, but no idea how old that is. Being where it is, it would be clean.
I'm leaving it on charge overnight, and maybe call in with somebody who can test the batteries properly tommorow, depending how time goes, but probably by end of week.
 
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Just had a thought..... The battery looks like it was replaced last year - before I owned the car. Did it need resetting/coding to the car somehow to tell it it's new? Or not?
 
Just had a thought..... The battery looks like it was replaced last year - before I owned the car. Did it need resetting/coding to the car somehow to tell it it's new? Or not?

No, it's just a case of replacing.

It sounds like the battery is too young to be duff although not impossible.

Saying that, you don't know what kind of life it had previously (stop/start from cold and never able to properly charge up).

I would also give it a proper charge overnight as recommended and see what the voltage is before you re-fit and then see how it goes.

Voltage isn't the whole story but it's a good indicator of battery condition.
 
These are the steps I took to restore the Start/Stop in my car after purchasing it from a Clueless seller who told me that the ECO Start/Stop only ever worked randomly for him and never kicked in as expected. Both batteries in my car 'looked' new, and the electric parking brake operated the 'hold' function normally.

#1 Ensure main battery working properly. I was annoyed to let myself be led astray by a local tyre shop who checked the charging system and told me it was faulty (they didn't understand/know about the smart charging feature so the charging voltage looked suspicious to them). So I replaced the battery (upon which they told me the charging was working properly again - probably because the charging system sensed thet the new battery needed charging as it has been sitting on the shelf?).

#2 Ensure the Aux battery is in good working order - on mine, the Aux battery looked new and held a healthy voltage. But the charging system knew that it wasn't holding a sufficient charge to run the critical electronics during a start/stop cycle. Mine was dated 2011, so replacing that immediately restored my ECO start/stop function.

#3 I found a couple of other error codes which I couldn't clear with my icarsoft scanner, but thankfully these error codes did not interfered with the ECO start/stop function.

Good luck with your investigation.
 
Thanks again wongl

Have just removed clamp on my aux battery and it has 12 13 stamped on it. I assume this means Dec 2013?

Also, after searching online, I think that "On-board electrical syatem" is specific to the aux battery. Not 100% sure, but enough to convince me to replace it. I think the other is "Starter electical system" for big battery.

After going onto Varta battery search, it's coming back with an upgraded one (which is what I'd have gone for anyway), but it's AGM. 513 106 020 | Varta Automotive

Do I really need AGM for this purpose?
 
After looking, most of them are AGM.

Have decided to order Exide EK131 AGM Car Battery Although I'm confused whether it's 12Ah (as per some descriptions - even on Exide site) or 13Ah (as per all photo's of one I've seen)

Will report back in a week when fitted :thumb:
 
I’d expect the main battery to be AGM, as they are for stop/start cars. I’m not familiar with the auxiliary battery, but it makes charging simpler as both need the slightly higher voltage charge.
 
Thanks again wongl

Have just removed clamp on my aux battery and it has 12 13 stamped on it. I assume this means Dec 2013?

Also, after searching online, I think that "On-board electrical syatem" is specific to the aux battery. Not 100% sure, but enough to convince me to replace it. I think the other is "Starter electical system" for big battery.

After going onto Varta battery search, it's coming back with an upgraded one (which is what I'd have gone for anyway), but it's AGM. 513 106 020 | Varta Automotive

Do I really need AGM for this purpose?

Mine is an original MB battery made by FIAMM in Italy (rated 12v 12Ah and 170A EN) and not Varta - it does not say AGM, but on the FAIMM website the equivalent size/spec FIAMM battery is stated as AGM which makes sense since the smart charging system will be used to charge both batteries in the car which means that both batteries will be charged intermittently (using a charging voltage capped below 14.8V) instead of being charged constantly. This means that AGM battery should give a better lifespan in such an environment.

Mine is mounted on its side (i.e. terminals horizontally instead of vertically), so I decided to stick with FIAMM since the Varta spec did not mention if their batteries have been designed to operate in a horizontal position.
 
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Feedback finally.

Fitted new battery this morning after some drama of cables touching!

It is now all green and ok with stop/start working well, we'll see how long before I get cheesed off with it, lol.

I fitted an AGM Exide bike battery 18Ah 230A, it's a little taller and I had to extend the thread securing the battery clamp.
 
£49. Delivered
 
£49. Delivered
Well done, and great to hear that your ECO Start/Stop is working again.

That is a great price - the space in my R172 is super tight and I went for an original MB battery just to be sure that it will fit. The battery from MB HK cost me circa GBP120! MB parts in HK are typically twice that in UK.
 

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