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Tesla Model S 2014 HV Battery issue

Hi, I have a Model S 2014 P85+

Last Monday I was driving it near from my house in Guatemala, but the car suddenly stoped with the warning: “Unable to drive, supply voltage too low”… I thought that would be a 12V battery failure, so, on my own, I replaced it for a new one. Yesterday, after installed it, the car woke up with 13 alerts on it, so I put it on “Service Mode” and take some pictures of the screen (please find them attached to this email),

2.jpeg


The more stressful alert for me was: BMS_f080_SW_Int_HV_Disconnect: the BMS has detected that the HV battery pack voltage differs from the sum of the brick voltages, making the HV battery unavailable for charging, driving or supporting the LV battery…

It look like is something is either not connected completely or properly from the battery, or maybe a problem with the HV battery itself?

Can somebody help me, where should I start to solve this problem?

Thanks a lot for your valuable help!

Juan Carlos
 

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Alert codes shows DCDC codes and Cabin PTC heater code. Looks like the HV circuit has faults and HV battery contactor not closing. So 12V will go flat and die quickly without recharge from HV battery.

Cabin PTC heater would be the first area to chase with these alerts. Could be as simple as unplug and unplug its connector from the DCDC (make sure know how to handle deadly HV system of course) due to moisture corrosion in the connector, or dead PTC cabin heater, or PTC cabin heater fuse in side DCDC etc etc.

If really want to peek inside the HV battery, use a CANBUS scanner setup like ScanMyTesla. Have 12V charged up (so CANBUS runs) and see what BMS reports on pack internal sensors such as the 6 voltage readings per module x 16 modules.
 
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Did you find the solution?
Not yet. A couple of weeks after my last post (dated on October 28th), It apperead another fault: BMS_F123 (Low HV internal isolation when pack contactors are open). I am puzzled since when it appeared, fault BMS_F080 disappeared...

Last week I dismounted the battery pack to change the HV Fuse, I saw no evidence of moisture on the top neither inside the front housing of the pack, so decided to mounted again in the car but BMS_F123 doesn't dissapereaded at all...

Attached some photos of the procedure,

Any Ideas?

Thanks a lot,

Back side of the Pack.jpeg BMS Connector check.jpeg Front HV Battery Pack module.jpeg HV Battery Pack dismounted 1.jpeg HV Battery Pack dismounted 2.jpeg HV Battery Pack dismounted 3.jpeg HV Battery Pack dismounted 4.jpeg HV Battery Pack melted fuse 1.jpeg HV Battery Pack melted fuse 2.jpeg New Pyrofuse Gen2 check.jpeg
 
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Alert codes shows DCDC codes and Cabin PTC heater code. Looks like the HV circuit has faults and HV battery contactor not closing. So 12V will go flat and die quickly without recharge from HV battery.

Cabin PTC heater would be the first area to chase with these alerts. Could be as simple as unplug and unplug its connector from the DCDC (make sure know how to handle deadly HV system of course) due to moisture corrosion in the connector, or dead PTC cabin heater, or PTC cabin heater fuse in side DCDC etc etc.

If really want to peek inside the HV battery, use a CANBUS scanner setup like ScanMyTesla. Have 12V charged up (so CANBUS runs) and see what BMS reports on pack internal sensors such as the 6 voltage readings per module x 16 modules.

Thank you very much for your advice.

Interesting, I will check the connections on the DC/DC converter,

I am not sure if the fuses of PTC, coolant heater and eAC of the Gen2 DC/DC converter are inside the case as the Gen1 DC/DC, do you know?

Since I have a fault BMS_F123 (low HV isolation when the contactors are open), according to Tesla procedure to troubleshooting HV ISO faults when the contactors are open and the BMS_ISO is bellow 1800kOhm, the ISO fault is inside the pack,

Even though I still haven't a measure of the BMS_ISO, I suspect that the
fault could be inside of the battery pack... might be contactors harness? the HV Link bus? ...

I already scan the battery by using Scan My Tesla APP and it seemed to me that the parameters of the 16 modules (96 measuments of voltage and temperature) are in between the expected values (please see attached photos). Also the voltage on the "head" of the battery sums the average of the 96 cells inside (please see the attached photos).

So I plan to dismount again the pack open the back and looking for anormal conditions, i.e. moisture, dust or components deformation, etc...

What do you think about that?

BMS ScanMyTesla 1.jpeg BMS ScanMyTesla 2.jpeg
 
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Since I have a fault BMS_F123 (low HV isolation when the contactors are open), according to Tesla procedure to troubleshooting HV ISO faults when the contactors are open and the BMS_ISO is bellow 1800kOhm, the ISO fault is inside the pack,

You are already far ahead of me in diagnostic knowledge :) And yes, I see Tesla HV isolation flow chart indicate HV battery when contactors open and < 1800kOhm.

I'm assuming besides BMS_F123 code, you do not hear any contactor sound?

I recently had HV problem and contactors didn't close. However the contactors made quieter sounds than usual. I spent some time understanding the 3 contactors (negative, pre-charger, HV +) I guess I only heard ground and precharge contactors connecting but not positive. Eventually, I unplugged and plugged coolant heater plug and HV+ contactor closed once again and car was fixed. So I concluded I had corrosion on coolant heater plug whhich prevented HV+ contactor from closing. Gen1 DCDC and these plugs has high moisture intrusion. Gen2 DCDC moved behind frunk I think. But Model S driver side wiper will pull water into passenger wiper spindle hole and dump water onto battery pack and that general area. I don't have gen2 DCDC to see how much moisture attack that area.

Here is my contact sound pattern when car would not go into drive.


You can read post #3-#5 on my analysis of what happened. Anyway, it is good to learn about -, precharge, and + contactors to help with diagnostic if you don't know already.


At least all your module voltages look okay so no module failures :)
 
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5JWX

Member
Oct 31, 2022
8
0
UK
Hi, I have a Model S 2014 P85+

Last Monday I was driving it near from my house in Guatemala, but the car suddenly stoped with the warning: “Unable to drive, supply voltage too low”… I thought that would be a 12V battery failure, so, on my own, I replaced it for a new one. Yesterday, after installed it, the car woke up with 13 alerts on it, so I put it on “Service Mode” and take some pictures of the screen (please find them attached to this email),

View attachment 868477

The more stressful alert for me was: BMS_f080_SW_Int_HV_Disconnect: the BMS has detected that the HV battery pack voltage differs from the sum of the brick voltages, making the HV battery unavailable for charging, driving or supporting the LV battery…

It look like is something is either not connected completely or properly from the battery, or maybe a problem with the HV battery itself?

Can somebody help me, where should I start to solve this problem?

Thanks a lot for your valuable help!

Juan Carlos
Hi Juan
I currently have the exact same issue as you on my 2014 model S.
Sorry to jump on your post but hoping we can assist each other.
Your battery cell reading look very healthy so dont think you have any issues there.
59F64B22-4661-459C-AC07-3DFD2BEBB09A.jpeg

I have my battery pack stripped.
Reading the isolation resistance from the car in service plus mode my resistance is only 80kohm so believe my fault is within the pack.

My first thought was the error just needed cleared but I don’t think toolbox allows this to be cleared, it wouldn’t give me access. Since than I found the low reading from can data so now want to physically check the readings at the pack.

Can anyone confirm the best way to read the isolation resistance from the pack? I was going to read from contactor input voltage B- to the “ground” and then B+ to ground of the pack should I be getting 3,000 Kohms?

I have previously checked the pyro fuse but I’m now thinking a blown fuse could be the cause of my low resistance as the pack would be open circuit?

The other thing I have noticed is the earth from body to HV models and HV battery pack rapid connection looks corroded but when doing a resistance test as 500v tests ok. Cannot find any info on these earths causing resistance issues yet!!
 
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You can read post #3-#5 on my analysis of what happened. Anyway, it is good to learn about -, precharge, and + contactors to help with diagnostic if you don't know already.

Interesting topics, you have done a great work documenting all your findings, much of this can help to apply preventive actions to avoid isolation problems (much of them comes from moisture and dust cumulating on the components connectors)...

I plan to check the HVIL starting at the PTC that is the most likely point of failure according to the statistics that Tesla manages (page 10 of the Tech Note: HVIL Diagnostic Guide), I will use your notes as guidance, thanks.
 
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You are already far ahead of me in diagnostic knowledge :) And yes, I see Tesla HV isolation flow chart indicate HV battery when contactors open and < 1800kOhm.

I'm assuming besides BMS_F123 code, you do not hear any contactor sound?

I recently had HV problem and contactors didn't close. However the contactors made quieter sounds than usual. I spent some time understanding the 3 contactors (negative, pre-charger, HV +) I guess I only heard ground and precharge contactors connecting but not positive. Eventually, I unplugged and plugged coolant heater plug and HV+ contactor closed once again and car was fixed. So I concluded I had corrosion on coolant heater plug whhich prevented HV+ contactor from closing. Gen1 DCDC and these plugs has high moisture intrusion. Gen2 DCDC moved behind frunk I think. But Model S driver side wiper will pull water into passenger wiper spindle hole and dump water onto battery pack and that general area. I don't have gen2 DCDC to see how much moisture attack that area.

Here is my contact sound pattern when car would not go into drive.


You can read post #3-#5 on my analysis of what happened. Anyway, it is good to learn about -, precharge, and + contactors to help with diagnostic if you don't know already.



At least all your module voltages look okay so no module failures :)
At least this are good news, isn't? :)
 
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My first thought was the error just needed cleared but I don’t think toolbox allows this to be cleared, it wouldn’t give me access. Since than I found the low reading from can data so now want to physically check the readings at the pack.

Yes, this is what we need to do. First thing is to know if the failure is internal or external at the battery pack. The Tech Note: Troubleshooting Isolation Faults, states that when the contactors are open the isolation measurement should be greater than 1800kOhm, so defenitely you and I have an low HV internal isolation in our battery packs... Basically an isolation issue is an HV conduction path to the chassis, so that this is a critical situation for the car's operation and the BMS prevent the contactors to close this avoid that DC/DC supports the LV circuit so the 12V battery becamo discharged.

HV isolation problems have three possible sources: 1) a physical defect of the insulation material in the HV loop (contactors harness, HV Link, etc.), 2)
contamination (of any size, i.e. dust, bolts, etc.), and/or 3) moisture. Deppending on what is the root cause the isolation problem would be the measure of the isolation (i.e. a short circuit to chassis would be a very low resistance to ground).

Now to fix this issue we definitelly need to check inside the pack looking for any of the above posible causes of the low isolation measurement, what do you think about that?

Experts please your thoughts are very valuable!
 
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Can anyone confirm the best way to read the isolation resistance from the pack? I was going to read from contactor input voltage B- to the “ground” and then B+ to ground of the pack should I be getting 3,000 Kohms?
In fact, as your battery pack has the contactors open, the BMS_Isolation_Resistance of 80kOhm you are reading is your battery pack internal isolation . The expected value is at least 1800kOhm (4% of the expected value)..
 
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I have previously checked the pyro fuse but I’m now thinking a blown fuse could be the cause of my low resistance as the pack would be open circuit?
As far as I know, an open circuit tends to increase your resistance...

This is just a hypothesis, but I think the lower the resistance (according to Tesla Benchmark, your internal resistance is 4% of the expected value), the more likely it is an insulation fault somewhere on the HV internal bus (likely at the back of the pack where the contactors are located and/or near the fuse in the front side). You can also check the internal voltages and temperatures of the cells in your your pack (you can use ScanMyTesla APP for example), to looking for low voltages or hot points that would be related with moisture or dust... this, to check all the possibilities,..

I would appreciate you can report here your findings and possible solution to your problem as I will, so that we can learn from each other and the same time sharing the knowledge with the members of the forum.

Opinions on the matter are very appreciated!

Thanks so much!
 
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5JWX

Member
Oct 31, 2022
8
0
UK
21117546-4B1E-4C97-94B8-715A4B75BD6C.jpeg


Not sure say to photograph but attached picture of corroded earth to HV rapid disconnect. I’ve not removed it but it looks like this is how the main centre pin earths to the chassis.

I accessed service mode plus through toolbox, paid 1 day licence fee & left it in plus mode, not sure if I will have to pay another subscription to get it back out when I’ve resolved the issue.

Tested my fuse & appears ok.
Will do further tests but may take a few days before I have time.

JCM_76

I’d definitely check your resistance at the rear motor with the battery pack back in before stripping your pack.
 

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Thanks for the photos, certantly the ground cable looks corroded, might be would be good to change it as a preventive action, but I think this isn't causing your low HV isolation, since your contactors are open and the rapid mate is downstream the measurement point...

I'm interested in to access to service mode plus but I don't know how to pay for the one-day license fee... did you access from the service webpage of Tesla? I see there only suscriptions for a month (US$500) and a year (US$3000)... It would be nicely to pay only for a day and go straight to read the BMS isolation resistance as you did,

Good news with your fuse... is it a first gen fuse or a pyrofuse? I changed mine for a second generation last week...

Please keep in touch so that we can share knowledge on how to fix our cars,,, definetelly next step after to fix them would be to check the HVIL including the rear motor,

Best regards,
 
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5JWX

Member
Oct 31, 2022
8
0
UK
Thanks for the photos, certantly the ground cable looks corroded, might be would be good to change it as a preventive action, but I think this isn't causing your low HV isolation, since your contactors are open and the rapid mate is downstream the measurement point...

I'm interested in to access to service mode plus but I don't know how to pay for the one-day license fee... did you access from the service webpage of Tesla? I see there only suscriptions for a month (US$500) and a year (US$3000)... It would be nicely to pay only for a day and go straight to read the BMS isolation resistance as you did,

Good news with your fuse... is it a first gen fuse or a pyrofuse? I changed mine for a second generation last week...

Please keep in touch so that we can share knowledge on how to fix our cars,,, definetelly next step after to fix them would be to check the HVIL including the rear motor,

Best regards,
I’m in the UK, we can currently get toolbox3 for 1 hour - £33 1 day - £120, 1 month £400, 1 year - £3,000. Prices vary don’t know if it’s the exchange rate or Tesla adjusting it.
The Toolbox software isn’t the best. If I were you I would defiantly remove the HV cover on the rear motor & see what resistance you’re getting. You may have a fault battery heater. You can fairly easily then unplug the battery heater, air con etc one at a time & re test or check the HV consumers directly.
 
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