[tarunjain]

Background

Hello folks, I have a Nexon EV Max:
- Nov 2022 manufactured
- Took delivery on 26th Jan 2023
- Driven 2150 kms so far
- I drive only in the city
- I do only slow AC charging, using the 3.3KW home charger
- First free service done at 1900 kms

I have done around 6-7 charging cycles so far. As recommended, I usually go till 10% battery and then let the battery charge till 100%. As I don't take the car on long trips, this is doable for me almost every time.

I am happy with the car's performance so far and also getting a pretty good real world range - 280 to 310 from 90% battery (100% to 10%). This is in line with what I have heard most other Nexon EV Max users get. So this isn't a cause of concern. Moreover, the battery consumption and charging, both are quite linear in nature. While charging, the battery %age increases very linearly with time. Similarly, while driving, the number of kms I get out of every %age point is very consistent. So there aren't any "SOC drops" etc. Below is the SOC graph from last month:



There isn't anything wrong seen in the graph, as far as I can tell. All looks pretty normal and healthy.

The Issue

There is just one issue I am facing with the car. Every time the battery reaches 10%, car goes in "limited performance" (limp/turtle) mode, which is normal. But then within 2-3 kms, before even reaching 9%, it shows HV System Fault. As far as I know, this HV System fault is expected only once the car reaches 0% battery. But in my case, I am getting it at 10% battery itself. Here is a video (gif) of the same:



However the car remains drivable. Except the error flashing in the instrument cluster, nothing changes in the behavior of the car. So the last time it happened, I switched off the ignition and turned on the car again. The HV system fault went away, but reappeared after driving for another few hundred meters. Repeated the same a couple more times, then parked and put it on charging.

Experience at the Tata service center

I reported this issue at the service center when I took the car for first free service. At the time, I didn't have this video to show to them. I had explained only verbally. But they neither seemed to know enough, nor interested enough to be able to help. After explaining the issue three times and insisting for some response, they just were responding with few terms they are familiar with - "SOC drop" etc.

I asked them if there were any error logs available which they could access but they refused. Upon insisting, the only way to diagnose they suggested is that I leave the car with them, they will charge it to 100%, then drive around for few days till it reaches 10% and collect some "parameters" throughout, send them to Tata and then wait for a response from Tata.

I am least interested in leaving the car in their incompetent hands for so long, especially given that the car isn't giving me any trouble in real usage (driving below 10% is not something I need to do ever because I don't take the car on long drives). For all I know, they also understand this and hence suggested this approach to shut me up and shoo me away

Has anyone here experienced anything similar? Any suggestions on what can be done? There isn't any urgency at my end because as I explained, the car is working absolutely fine from 100% to 10% (at least so far). Even after that, although I have tried for only a few kms, except the flashing error on the instrument console, there is nothing else wrong with how the car drives.

[Sridhar C E]

Originally Posted by tarunjain

Background

Hello folks, I have a Nexon EV Max:

The Issue


Has anyone here experienced anything similar? Any suggestions on what can be done?.

This kind of an issue begs for the attention of the manufacturer. I wish Tata Motors opens a window for dialog with a reputed body of its customers (like Team BHP).

If either we from TBHP or Tata Motors took the initiative to open a communication channel such issues, especially pertaining to a relatively new technology/product can get the attention they deserve. This is not something we can rely on the dealer/service partner to take up with the manufacturer.

[DRPSREDDY]

My car too is a Nexon EV MAX. I too have driven the car till 6% battery for a couple of cycles. I rarely have gone below 15% and immediately keep it on charging. I use mostly the 7.2kw charger. I never faced the issue.

This surely needs attention. Please let the charge go below 40% and then hand over the car. They do some Diagnostics on the car. Maybe they will escalate it to TATA Motors and get some info. Till now most of the ASC guys are clueless about the EVs

[s10]

Has anyone here experienced anything similar? Any suggestions on what can be done? There isn't any urgency at my end because as I explained, the car is working absolutely fine from 100% to 10% (at least so far). Even after that, although I have tried for only a few kms, except the flashing error on the instrument console, there is nothing else wrong with how the car drives.

You can try resetting the BMS. Disconnect the -ve terminal, wait for 10 mins and then reconnect. It will reset things to default, hopefully this should correct that.

[arpanjha]

Originally Posted by tarunjain

Background



The Issue

There is just one issue I am facing with the car. Every time the battery reaches 10%, car goes in "limited performance" (limp/turtle) mode, which is normal. But then within 2-3 kms, before even reaching 9%, it shows HV System Fault. As far as I know, this HV System fault is expected only once the car reaches 0% battery. But in my case, I am getting it at 10% battery itself. Here is a video (gif) of the same:

Attachment 2427829

However the car remains drivable. Except the error flashing in the instrument cluster, nothing changes in the behavior of the car. So the last time it happened, I switched off the ignition and turned on the car again. The HV system fault went away, but reappeared after driving for another few hundred meters. Repeated the same a couple more times, then parked and put it on charging.

I am a max owner like you, I have driven about 5600 Km till now from 09th December. Till now I have gone below 10% 5 times, and once just as soon as SOC reached 10%, first limited performance message came, and then HV fault code came, but went away immediately, but the throttle response was locked to very low level, I guess this comes <5%. Although car was just at 9% then. I stopped at a shop very close to home to get stuff, I had switched off the car and locked, when I returned in 10 mins, started the car, the HV fault code did not appear. Just the Turtle was there, AC, throttle and everything else was normal.
Once I had taken the car down to 5% charge, no HV fault had come, just the limited performance note with the turtle. But the next morning when I started the car from 100% charge, the HV fault code appeared, and disappeared almost immediately.
Barring these two occasions, I haven't seen these, and I am not at all bothered about these, since they have not affected anything practically. Maybe some bug which needs attention to be cleared in future. I am sure, the data has been automatically logged to Tata, and I hope in future updates these will be cleared.

[tarunjain]

Originally Posted by s10

You can try resetting the BMS. Disconnect the -ve terminal, wait for 10 mins and then reconnect. It will reset things to default, hopefully this should correct that.

I am a bit wary of doing this myself. (Is the procedure described in the manual somewhere?) However, I too suspect an issue on the same lines. It appears to be a software level issue rather than any physical issue with the battery.

Somehow most responses I got so far on Tata EV groups and even from the service advisor at Tata Motors SC, everyone directly suspects the battery. I am not convinced that's the case. Battery remains very well behaved (no SOC drops, etc.) even while the HV System fault is flashing. That's why I don't want to unnecessarily leave it at the SC and initiate an investigation in the wrong direction. Given that it's not giving me any trouble within the usable window of the battery (100% to 10%), I intend to just wait it out till either someone at Tata motors offers a logical sounding explanation, or till the next software update (which may lead to the issue disappearing on its own).

Originally Posted by arpanjha

Barring these two occasions, I haven't seen these, and I am not at all bothered about these, since they have not affected anything practically. Maybe some bug which needs attention to be cleared in future. I am sure, the data has been automatically logged to Tata, and I hope in future updates these will be cleared.

Exactly. It feels like a software issue to me as well. However the only difference compared to issue you saw on your car is that it doesn't go away on its own. It goes away when I turn off the car and turn on again. But appears again after driving for few hundred meters.

[s10]

Originally Posted by tarunjain

I am a bit wary of doing this myself. (Is the procedure described in the manual somewhere?) However, I too suspect an issue on the same lines. It appears to be a software level issue rather than any physical issue with the battery.

Somehow most responses I got so far on Tata EV groups and even from the service advisor at Tata Motors SC, everyone directly suspects the battery. I am not convinced that's the case. Battery remains very well behaved (no SOC drops, etc.) even while the HV System fault is flashing. That's why I don't want to unnecessarily leave it at the SC and initiate an investigation in the wrong direction. Given that it's not giving me any trouble within the usable window of the battery (100% to 10%), I intend to just wait it out till either someone at Tata motors offers a logical sounding explanation, or till the next software update (which may lead to the issue disappearing on its own).



Exactly. It feels like a software issue to me as well. However the only difference compared to issue you saw on your car is that it doesn't go away on its own. It goes away when I turn off the car and turn on again. But appears again after driving for few hundred meters.

Even tata guys with their so called expert knowledge will do the same thing . I have explained my experience here #post5498637 (Review: The Tata Nexon EV)

[Aditya]

Tata Nexon EV Max shows HV System Fault even before battery reaches 9% - Posts moved to a new thread.

[prasanna_indaje]

Originally Posted by tarunjain

[
Has anyone here experienced anything similar? Any suggestions on what can be done? There isn't any urgency at my end because as I explained, the car is working absolutely fine from 100% to 10% (at least so far). Even after that, although I have tried for only a few kms, except the flashing error on the instrument console, there is nothing else wrong with how the car drives.

Having experience of getting HV battery replaced for my Nexon EV, I would suggest you to talk to TaMo regional Service head directly.
Service centers are not capable of handling most of the HV battery related issues.

[pradeepkc]

Originally Posted by tarunjain

Background

I asked them if there were any error logs available which they could access but they refused. Upon insisting, the only way to diagnose they suggested is that I leave the car with them, they will charge it to 100%, then drive around for few days till it reaches 10% and collect some "parameters" throughout, send them to Tata and then wait for a response from Tata.

Could you try insisting on reading the DTCs codes and messages through their OBD2 software? You can read up on these and impress upon them to give you just the DTCs and that you will pay for the scan.

[arpanjha]

Saga continues, this morning when I got into the car and started the car to leave for work, SOC was at 52% and "Limited Performance" mode got activated, with multiple symbols lighting up, Limp mode symbol, Service Indicator etc. all coming up and blinking constantly. I powered the car off, and powered on again, issue solved.
But I do not understand, such errors or bugs are constantly getting uploaded via telematics, why does it take so long for Tata to resolve these? Imagine such things coming up while driving at high speeds?
I decided to buy the NEV fully aware of the fact that early adopters are all Beta testers, and I agreed for the same, expecting Tata to slowly go through these feedback and correct at the earliest point. But unfortunately the front line Tata service advisors just are not trained enough to analyze these things. Tata has got enough no. of cars on the road and more than enough data now to solve these silly bugs. Although it is not frustrating me right now, but slowly my confidence is going down.

[vijayvb]

Did Tata give a solution anyone? Its happened again for me for the second time. First time it went away after leaving the car locked for an hour and trying again.

[ferrarirules]

Originally Posted by tarunjain

Background

Has anyone here experienced anything similar? Any suggestions on what can be done? There isn't any urgency at my end because as I explained, the car is working absolutely fine from 100% to 10% (at least so far). Even after that, although I have tried for only a few kms, except the flashing error on the instrument console, there is nothing else wrong with how the car drives.

Another BHPIAN Prateek was facing the same issue, his car's battery was replaced by Tata. Please check this thread - link (HV Battery Fault at 10 months in my Nexon EV Max | Tata’s quick response)

You can get in touch with him as well. They kept his car and called a Tata designated battery expert to run some tests on the battery

[navinmra]

Originally Posted by tarunjain

Background


I have done around 6-7 charging cycles so far. As recommended, I usually go till 10% battery and then let the battery charge till 100%. As I don't take the car on long trips, this is doable for me almost every time.

I just bought a Nexon EV Max Dark edition 2 weeks ago. My two cents: Keep the battery charge between 30% to 70% i.e. charge when the SOC is at 30% and stop at 70% on a slow charger. And every 5 such cycles do a full charge to 100% so that BMS does cell balancing.

[Rakarocks]

Originally Posted by tarunjain

I have done around 6-7 charging cycles so far. As recommended, I usually go till 10% battery and then let the battery charge till 100%. As I don't take the car on long trips, this is doable for me almost every time.

Exactly the same issue multiple times on Nexon EV prime 2021. Same weird advice given by service center guys. The limp mode is supposed to get activated at 10% SOC. But it’s getting activated at 24% SOC and soon after moves to HV SYSTEM fault