Tata Nexon EV Max: HV system warning error and poor response from Tata

Every time the battery reaches 10%, the car goes into limited power (limp/turtle) mode, which is normal. But then within 2-3 km, even before reaching 9%, it shows HV system error.

BHPian tarunjain recently shared with other enthusiasts.

background

Hi guys, I have a Nexon EV Max:

• Manufactured Nov 2022
• Delivery on 01/26/2023
• Driven 2150 km so far
• I only drive around town
• I only charge slowly with AC using the 3.3kW home charger
• First free service at 1900 km

I’ve done about 6-7 charge cycles so far. As recommended, I usually go to 10% battery and then let the battery charge to 100%. Since I don’t use my car on long journeys, this is almost always possible for me.

I’m happy with the car’s performance so far, and I’m also getting a pretty good range in the real world – 280 to 310 at 90% battery (100% to 10%). This is consistent with what I’ve heard from most other Nexon EV Max users. So that’s nothing to worry about. In addition, battery consumption and charging are both fairly linear. During the charging process, the battery level increases very linearly over time. Likewise, the number of kilometers I get out of each percentage point is very consistent while riding. So there are no “SOC dips” etc. Below is the SOC chart from last month:

There is nothing visible on the graph as far as I can tell. Everything looks pretty normal and healthy.

The topic

I only have a problem with the car. Every time the battery reaches 10%, the car goes into limited power (limp/turtle) mode, which is normal. But then within 2-3 km, even before reaching 9%, it shows HV system error. As far as I know, this HV system error is not expected until the car reaches 0% battery. But in my case I get it even at 10% battery. Here is a video (gif) of it:

But the car remains drivable. Except for the error flashing in the instrument cluster, nothing changes in the behavior of the car. The last time it happened I turned off the ignition and restarted the car. The HV system error was gone, but reappeared after a few hundred meters of driving. Repeated the same thing a few more times, then parked and charged.

Tata Service Center experience

I reported this problem to the service center when I took the car to the first free service. At the time, I didn’t have this video to show them. I had only explained it verbally. But they didn’t seem to know enough or care enough to be able to help. After explaining the issue three times and insisting on an answer, they responded with just a few terms they are familiar with – “SOC waste” etc.

I asked them if they had error logs available to access, but they declined. If they insist, the only way they suggest to diagnose is that I leave the car with them, they charge it to 100%, then drive around for a few days until it reaches 10%, collecting some “parameters” along the way and 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 since the car gives me no problems in real world use (driving below 10% is not something I ever have to do because I don’t take the car on long journeys). As far as I know, they understand that too, so they proposed this approach to silence me and shoo me away

Has anyone here experienced something similar? Any suggestions what can be done? There is no urgency from my side, because as I said, the car works absolutely flawlessly from 100% to 10% (at least so far). Even after that, although I’ve only tried it for a few miles, there is nothing else to do with the car’s handling other than the flashing error on the instrument panel.

Here’s what BHPians Sridhar_C_E had to say:

This type of problem needs the attention of the manufacturer. I wish Tata Motors would open a window for dialogue with a prestigious group of its customers (like Team BHP).

If either we at TBHP or Tata Motors take the initiative to open a communication channel, such issues, especially in relation to a relatively new technology/product, can get the attention they deserve. We cannot rely on the dealer/service partner asking the manufacturer about this.

Here’s what DRPSREDDY had to say:

My car is also a Nexon EV MAX. I also drove the car down to 6% battery for a few cycles. I’ve rarely gone below 15% and let it charge right away. I mostly use the 7.2kw charger. I have never dealt with the problem.

This certainly requires attention. Please let the charge drop below 40% and then drop off the car. They do some diagnostics on the car. Maybe escalate it to TATA Motors and get some information. Until now, most ASC people have no idea about EVs

Here’s what BHPian Arpanjha had to say:

I’m a Max owner like you, I’ve ridden about 5600km since December 09th. So far I’ve dropped below 10% 5 times and once as soon as the SOC reached 10% the first message came up about restricted performance and then the HV error code came up but it went away immediately but the throttle response was at a very low level Level locked , I guess that’s coming <5%. Although the car was just 9% at the time. I stopped at a shop very close to home to get things, I had turned the car off and locked it, when I came back in 10 minutes, started the car, the HV fault code didn't appear. Only the turtle was there, air conditioning, gas and everything else was normal.

After I shut down the car to 5% charge, there was no more HV error, only the limited performance rating with the turtle. But the next morning when I started the car with 100% charge, the HV error code appeared and disappeared almost immediately.

Other than those two occasions, I haven’t seen these, and these don’t bother me at all as they didn’t affect virtually anything. Maybe a bug that needs to be fixed in the future. I am sure that the data was automatically logged to Tata and I hope that this will be deleted in future updates.

Read the BHPian comments for more insight and information.