Tata Nexon EV Max: HV system warning fault & Tata's poor response

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.

BHPian tarunjain recently shared this with other enthusiasts.

Backgroun

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.

Here's what BHPian Sridhar_C_E had to say on the matter:

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.

Here's what DRPSREDDY had to say on the matter:

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

Here's what BHPian arpanjha had to say on the matter:

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.

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