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Discussion Starter #1
Hello everyone.

TL;DR version:
  • is there a way to test the DC-to-DC converter?
  • what is the latest and greatest way to read and clear codes on our cars? I searched this Forum and found recommendations for some tools, but some of the threads seem outdated and I wonder if there are units out there that are known to work well with our cars.
  • do we have the knowledge to reset the 12V battery age counter in the ECU, should I decide to replace it?

Backstory:
I am the original owner of this car, it's my daily driver. A few days ago the car displayed the "HV System -> Workshop" message on the dash and started behaving erratically, similar to an ICE vehicle with bad alternator (flickering, low power accessories, etc).

From there, things escalated quickly. The remote and accessories stopped working, I got in the car using the key and did some basic troubleshooting:
  • voltage at the 12V battery: 6.x Volts
  • disconnected the 12V battery and connected a low amp battery maintainer overnight
  • voltage at the 12V battery the following day: 4.x Volts (voltage actually dropped)
  • connected a regular car charger (maybe 20 Amps?) and charged the battery for a couple of hours, battery got to the mid 12V range without issue
  • reconnected battery terminals, car was working like nothing happened ("HV System -> Workshop" message still displayed)
  • plugged Level 1 charging cable (the one that came with the car) on slow setting (I almost always use the slow setting anyway) and measured voltage at the battery terminal, it was around 13.5V, so it seemed to me like the "alternator" (DC-to-DC) was doing its job.

Yesterday I called my local stealership (where I bought the car 5+ years ago) and told them about the issue and that I wanted to take the car in to get the HV system checked. The service advisor said there would be a $135 diag fee. I reminded him that I have BAP and that they own the battery and the HV system, he said there was still going to be a $135 diag fee, and then depending on the result it could have been refunded.

I am not even going to get into the amount of misinformation and poor customer care that these folks offer, it might take a couple of phone calls, but I know that they will diagnose the HV system as part of the BAP coverage, no major concerns there. The car charges and drives without issue, but here's when it got scary... I plugged in the car last night. This morning, I went to unplug the charger and noticed a strong, weird smell inside the car. It wasn't a plastic/burn smell, it almost smelled like some sort of food. So I lift the passenger side mat, remove the foam cover and was greeted with this:


I immediately unplugged the scalding battery and pulled it from the car for fear it would catch on fire. Got a liquid (presumably acid) on my hands, but at least the the battery was out of the car (it continued to vent for a while after that).

I clearly have to take the car in to get the HV System checked, but I'd like to do as much diagnosis on my own as possible on my own first, since the folks at my local stealership are either misinformed, or thieves (or, more likely, a little bit of both). I want to go in with a better idea on what happened, need to document as much as possible in order to have them service the HV System for free and not touch anything else.

If anyone has answers to my TL;DR questions above, I would be immensely grateful.

Thanks in advance!
 

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I can see the elbow for the vent tube that plugs into the battery, but I can't see the tube itself. Is it there?

Len
 

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^ what he said the tube for the battery vent is missing from the looks of it.
These batteries will vent when charging due to the way the reaction does in the acid.
Now if you have a load tester(or access to one) you can load test the battery to see if it tests out bad(load tests always reveal a bad battery)
 

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Discussion Starter #4
I can see the elbow for the vent tube that plugs into the battery, but I can't see the tube itself. Is it there?
Hi Len. Yes, it is there.

^ what he said the tube for the battery vent is missing from the looks of it.
These batteries will vent when charging due to the way the reaction does in the acid.
But is it normal to vent that much? I never smelled anything like that around the car before, does the vent tube go through a carbon activated filter, perhaps?

Now if you have a load tester(or access to one) you can load test the battery to see if it tests out bad(load tests always reveal a bad battery)
Thank you, I did plan on taking the battery to get load tested.

Does anyone know if there's a way to test the DC-to-DC converter? I would hate to put a new battery only to have it damaged by a faulty converter.

Also... does anyone know if we enthusiasts have a way to reset the battery age counter in the ECU?
 

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You could possibly use a multi meter with power to the charge port(with a 12 volt battery in place) and see what the voltage is at the terminals)
13.2-13.5 should be normal.
It may be bad but a load test will reveal it.
Mine was weak and it had vented some(though the tube was in place and no smell was in the car)
 

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Discussion Starter #6
  • plugged Level 1 charging cable (the one that came with the car) on slow setting (I almost always use the slow setting anyway) and measured voltage at the battery terminal, it was around 13.5V, so it seemed to me like the "alternator" (DC-to-DC) was doing its job.
You could possibly use a multi meter with power to the charge port(with a 12 volt battery in place) and see what the voltage is at the terminals)
13.2-13.5 should be normal.
I did. I don't remember the exact value, but it was in the mid 13s, which led me to believe that (at least at that moment) the battery was being charged correctly.

Mine was weak and it had vented some(though the tube was in place and no smell was in the car)
This is interesting. How do you know it had vented, could you smell something in the garage, or perhaps did you see some form of drip on the floor?
 

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Replace the 12 V and go from there would be my next course of action. When you connected the battery maintainer with the open circuit and voltage dropped the next day it shows sign of internal short. That battery is cooking and luckily didn't explode....

Sent from my moto g(7) power using Tapatalk
 

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I had to temporarily take it out to store the car for a few months and it was weak when I took it out(sluggish cranking) and it had a bit of stuff on the side when I took the vent tube out.
I did notice a slight smell of where it had vented some also but it went away quickly.
Charged it up afterwards so it wouldn’t go bad.
Yours is most likely toast if it’s not holding a charge.
Btw they don’t explode unless the outside terminals were to be contacted otherwise it just would go dead quick or fail a load test.
 

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MY08 cabrio MY09 cabrio Brabus MY15 ED
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I am the original owner of this car, it's my daily driver. A few days ago the car displayed the "HV System -> Workshop" message on the dash and started behaving erratically, similar to an ICE vehicle with bad alternator (flickering, low power accessories, etc).

Yesterday I called my local stealership (where I bought the car 5+ years ago) and told them about the issue and that I wanted to take the car in to get the HV system checked. The service advisor said there would be a $135 diag fee. I reminded him that I have BAP and that they own the battery and the HV system, he said there was still going to be a $135 diag fee, and then depending on the result it could have been refunded.

I am not even going to get into the amount of misinformation and poor customer care that these folks offer, it might take a couple of phone calls, but I know that they will diagnose the HV system as part of the BAP coverage, no major concerns there. The car charges and drives without issue, but here's when it got scary... I plugged in the car last night. This morning, I went to unplug the charger and noticed a strong, weird smell inside the car. It wasn't a plastic/burn smell, it almost smelled like some sort of food.

I clearly have to take the car in to get the HV System checked, but I'd like to do as much diagnosis on my own as possible on my own first, since the folks at my local stealership are either misinformed, or thieves (or, more likely, a little bit of both). I want to go in with a better idea on what happened, need to document as much as possible in order to have them service the HV System for free and not touch anything else.
MY15 ED, with original 12V battery?

With BAP, MBFS owns and warrants (assuming annual maintenance to include desiccant cartridge) the rented HV battery.

YOU own the sled, the 12V and the HV "system." Probably need a new 12V but i don't think that will clear the "HV System -> Workshop" error message. May not be advisable to continue charge/drive while ignoring the error message?
 

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I have high confidence you need a new 12 V battery. You could use that $135 diagnostic fee towards the replacement. The fact that it was disconnected and charged means voltage should have gone up overnight, not down....

Btw they don’t explode unless the outside terminals were to be contacted otherwise it just would go dead quick or fail a load test.
I still have the roadside receipt for when a Mercedes brand battery exploded when I tried to start my car (‘92 190E) after Mass (Church). The roadside assistance guy did say he’d never seen that before, and besides me I haven’t heard of spontaneous explosion since. BUT, I never bought a Mercedes replacement battery from then on.

Crossing my fingers the problem is that simple....
 

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Discussion Starter #12
Replace the 12 V and go from there would be my next course of action. When you connected the battery maintainer with the open circuit and voltage dropped the next day it shows sign of internal short. That battery is cooking and luckily didn't explode....
True, but it could have been the battery maintainer as well. I have vague memory that that same brick did that to a lawnmower battery in the past. I wonder if it has a crappy charging algorithm when batteries have a very low voltage to begin with. I will mark it and keep a close eye on that charger from now on (I have several different models, and just got a new NOCO Genius10, which I connected tonight just to see what it does (battery is sitting outside).

I had to temporarily take it out to store the car for a few months and it was weak when I took it out(sluggish cranking) and it had a bit of stuff on the side when I took the vent tube out.
I did notice a slight smell of where it had vented some also but it went away quickly.
Charged it up afterwards so it wouldn’t go bad.
Yours is most likely toast if it’s not holding a charge.
Btw they don’t explode unless the outside terminals were to be contacted otherwise it just would go dead quick or fail a load test.
Yes, but it was venting pretty strong and the whole thing was very, very hot to the touch.

MY15 ED, with original 12V battery?
Correct.

With BAP, MBFS owns and warrants (assuming annual maintenance to include desiccant cartridge) the rented HV battery.

YOU own the sled, the 12V and the HV "system."
Interesting, I thought the HV "system" was included too. But yes, I am definitely aware that I own the rest, including the 12V battery. And yes, I haven't missed a single BAP-related maintenance.

Probably need a new 12V but i don't think that will clear the "HV System -> Workshop" error message. May not be advisable to continue charge/drive while ignoring the error message?
Agreed, certainly not planning on doing so. I just wanted to do as much due diligence as I could before taking her in, including installing a new battery if need be, I just need to figure out if I can reprogram it somehow.

I have high confidence you need a new 12 V battery. You could use that $135 diagnostic fee towards the replacement. The fact that it was disconnected and charged means voltage should have gone up overnight, not down....
I didn't know the $135 could be used towards the replacement, good to know in case I decide to go that route, thank you. And regarding the voltage going down... I am not saying the 12V battery is good (it's likely done with), but that voltage drop might have been caused by the maintainer itself, I vaguely recall one of my maintainers doing something similar to an old lawnmower battery a while back. Like I said above, it's been connected to a new NOCO Genius10 (very nice 'smart' charger) for the past few hours, I'll see how she looks tomorrow morning and go from there.
 

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If it’s cooled down try charging it(slow charging that is) then let the battery sit overnight then check to see if it’s losing charge the next morning.
If it’s holding a charge it means something in the car is draining if not then it’s done.
Had one go dead in my Miata multiple times(advance would say it was good each time I took it in) after having to coast start the car for the fourth time I took the battery out and let it sit after charging the next day I tested it and it was bad on a load tester.
If the battery has a internal short it will be below 12 volt in no time since one or more cells in it can’t hold a charge.
Got a replacement and it never gave me a problem.
 

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It seem to me that the only problem is the battery had an internal short. i presume that the "smoke" was water vapor from fizzing electrolyte? I don't see how the DC-DC converter could cause the battery to do this. If it failed, it would simply stop putting out any voltage at all - not putting out too high a voltage.

You might have just discovered the key clue of the HV battery "bricking" problem - the factory battery is prone to shorts - which completely discharges the HV battery if the car is left unattended with this condition for several days.

The DC-DC converter is integral with the inverter/controller - the big box over the motor. Probably very expensive to replace.

At any rate, you need a new battery to drive it to the dealer, so replacing the battery is the first step.
 

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I was thinking to spend the $135 on a new battery vs going in to get the car diagnosed, but I do recall that certain dealers' diagnostic fee could be used towards a repair....

Sent from my moto g(7) power using Tapatalk
 

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Do the battery first then if it still gives any messages then go.
If you can do it yourself it would come out cheaper in the long run provided it fixes the problem.
 

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So you say you have the BAP program that you're paying for each month. That requires an annual check up. When is the next one due? If it's getting close, let them do it and give you an indication if there is a problem with the HV battery. If there is, it's their nickel.

Len
 

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Discussion Starter #18
Good morning everyone, and thank you all for your replies.

Question: I am most definitely getting a new battery. Can anyone tell me if these cars need the "12V battery age counter" reset when a new battery is installed? If yes, do we enthusiasts have a way to do so? I wouldn't want to install a fresh 12V battery only to have it treated by the car like a 5yr old battery (charging algorithms, etc).

The NOCO Genius10 'smart' charger has been working on the old battery (in low-amp AGM mode) for the past 17 hours. The battery read 8V when I connected the unit, it now shows 11.4V, so it's slowly taking a charge. Only reason I am doing this is to gather more data. If this old one charges fully, I might put it in the car and do some spirited driving for 15-20 minutes to get the HV battery under 80%... even though I have BAP, I still try to take care of my HV battery and hate the idea of it sitting at 100% for prolonged periods of time (I still don't know which 12V battery I will be getting and how long it might take to arrive, I am researching that now).

It seem to me that the only problem is the battery had an internal short. i presume that the "smoke" was water vapor from fizzing electrolyte? I don't see how the DC-DC converter could cause the battery to do this. If it failed, it would simply stop putting out any voltage at all - not putting out too high a voltage.
I hope that's the case, Yinzer.

You might have just discovered the key clue of the HV battery "bricking" problem - the factory battery is prone to shorts - which completely discharges the HV battery if the car is left unattended with this condition for several days.
I wasn't aware of any "HV battery bricking" issue. Is it a common issue happening with our cars? Anyhow... yes, I try my best to keep my battery between 20%-80% as I am aware of the increased deterioration at the extremes of the spectrum.

Again, I appreciate the brainstorming and input! I wish everyone a great Sunday.
 

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Discussion Starter #19
So you say you have the BAP program that you're paying for each month. That requires an annual check up. When is the next one due? If it's getting close, let them do it and give you an indication if there is a problem with the HV battery. If there is, it's their nickel.
Hi Len. I had the last one done in late spring and only drove about 5000 miles since. Next one is due in another 5000 miles. Before the pandemic I would have driven those miles in no time, but I've been working from home for months now, so even if they go by a "miles or time, whichever comes first", it's still going to be a few months before the next check-up due date. Although I don't exclude it being on their dime anyway, due to the message on the dashboard.
 

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I don't have the BAP on either one of my cars, but I was always under the impression that it was time only, i.e. annually.

A replacement 12v battery is just a plug and play operation. No need to reset anything except to maybe enter the generic radio code. See the sticky at the top of the forum about replacing the 12v battery.

Len.
 
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