[pganapathy]

I really sympathise with you. My friend has an electric Nexon and it has never given him any problems whatsoever. He loves it as a city car. Seems to be a case of bad QC.

[aashishnb]

Request to everyone, since battery+motor is almost everything for an EVs, and unlike ICE, there are no child parts that can be replaced, if something came wrong from the factory:

1. Is there a way to check the battery & motor issues (via software obviously), like for e.g. using an OBD connector or some kind of a system generated report?
2. Are there any external service providers / engineers who can help do it during PDI?
3. During PDI, we should probably start asking them to generate a system check report & give, kind of similar to the one we do while buying a user car?
4. Would be helpful if we can add the codes/errors to check in the PDI checlist

[GST]

Originally Posted by sanjayrozario

As a former Tata Motors customer, I totally commiserate with your problems. QC is non-existent at the factory. Service Centres consist of a bunch of clueless folks. I sold my Harrier in 3 years because of the pain I was put through. Customer service is a fancy buzzword for them.

I had nearly put my money on Harrier until out of blue I ended up having to talk to a different service advisor than the one whom I jad contacted a couple of months ago. Then all the drama thrown by this service advisor made me realise the hassle I might be gambling for and dropped the idea. Now waiting for Nissan Qashqai, or might even think about Seltos or newer offerings from Honda. Fortunately, my car, Ciaz 2017, runs butter smooth even now without any hassles: I am changing it only due to safety concerns on highways now that my highway runs have increased due to the job.

[architect_santo]

My sympathies for then situation Tata has put you through sir, I’m sure they’d fix this issue, but the forthcoming path is bothersome!
Thank God, I was considering to buy an Tiago EV for my wife to drop my daughter at school. Since I have a Swift diesel, I thought I can get a EV as a second car, to be used only for the city runs. Now I guess it’s safe to stay away from an EV until Maruti Suzuki introduces one.
Was curious about that WagonR EV which Maruti was considering, but disappointing that they did not showcase that in the expo.
I also believe that the reliability offered by Japanese brands are far ahead of other brands. Considering Honda/ Toyota and also Nissan are concentrating only on hybrids for now, I guess there is no other option than to wait for MSIL.

[Nikhil Beke]

Before we indulge in whole-sale brand bashing exercise here, could we at least wait till a diagnosis in this particular case is reached? As any future EV consumer here would testify, the past posts by OP in this forum indicate his having done a lot of research before taking the informed decision of buying this car- this experience is hardly a representative one when it comes to Tata EVs. It would be unfair to single out a brand that has a bigger and better EV experience than all others (barring perhaps MG). These unfortunate teething issues would be there irrespective of the brand launching their own vehicles (if at all Japanese ever get around to launching one in India). I'm not contesting the fact that the dealer/OEM should be more forthcoming in troubleshooting these issues- it remains to be seen if that's the case. I don't see the point of reiterating ICE horror stories in this context (justified as it is, in their own review/ownership threads). As to other brands launching EVs-sans-niggles from the start, don't know what's stopping them- they're banking on the case studies of early adopters like OP and trying to learn from that experience, perhaps? Let's see if they're smarter than Tata in this regard- if they indeed are, we should be rewarded with better vehicles.

[pradeepkc]

You don't have a 12V battery issue because your instrument cluster is running when your car broke down. You most likely have issue with your HV Battery. One of the series in the battery pack is probably bad and causing a Cell UV or Cell Imbalance fault that's causing the BMS to shutdown while driving. Ask the service center to give you the error readout from the BMS (Battery Management System).

I understand it's a bad experience. Sometimes cells do go bad and causes the entire battery pack to shutdown before it causes any incident (There's 1000s of cells in a car). And a lot of the research is going on around trying to find the bad cell early on before it gets to the failure point. Some companies have it fairly figured out. But it's only going to get better. I wish Tata had trained their dealers better to handle any instance of bad HV Battery early on. The dealer clearly doesn't know how to deal with the error.

[Nanolover]

I did my research and choose an EV and did enjoy it till it broke down. My sore points basically are:

1. Inability to fix it on the first breakdown attempt. Dealer saying all is fine and return it to you , only for it to breakdown within 12 kms of driving back.

2. The need to escalate to all senior management for them to swing into action and take the car again for a total diagnosis. This time plant personnel are also involved.

3. Absolute lack of communication. THIS IS THE NUMBER ONE PROBLEM. Even now, I have to call them everyday and ask for the progress, instead of proactively keeping the customer updated on what is happening.

4. No limp home mode, at least for Tata EVs. If it breaks down, you are stuck where you are - at a desolate place, in a traffic signal or worse as it happened to me, in the intersection of MG road signal. More folks are interested in honking than coming to push and help ( understandable and all have busy lives). You wont realize the heart burn this gives when stranded in the middle of a junction with family on board.

5. The whole point of saving money on EV is now up in fumes. I have shelled out 4000 rupees till date for filling up Celerio with petrol, since that is doing my back up running. No courtesy car, nothing. So, if EV is the ONLY car in your family, what will you do? Rely on public transport till these wise guys figure out what is wrong with your car?

6. EV totally flummoxes petrol heads like us. You don't know what is wrong, you can only guess what is wrong and that too with various derivatives. At least for a fossil fueled car, you can sort of pin point where and what the problem is.

NOW UPDATE ON WHAT THE PROBELM MIGHT BE ( as heard from the technician handling it)

- There seems to be some problem with the wiring harness which sends signal between LV and HV battery? ( don't know this either)

- HV and LV battery are all OK.

- Car is still at the dealer , 4 days counting.

- Don't have any assurance on when it will be returned.

[i74js]

Off topic: In RC what do we get to see against Engine Number for an eV? Is there motor number or battery pack identification that is passed as an entry.

[tharian]

Originally Posted by Nanolover

- There seems to be some problem with the wiring harness which sends signal between LV and HV battery? ( don't know this either)

- HV and LV batteries are all OK.
.

Did you or they notice any rat ingress/droppings under the hood? Rat bite can be a possibility and probably the service center has a mind block that this is something complicated and has not bothered to check the basics.

On my sister's one-month-old MG ZS EV, back when she purchased it in 2020, we had this issue;
https://www.team-bhp.com/forum/elect...-review-3.html (3 Nights & 2 days with the MG ZS EV - Extended Test Drive & Review)

Posts 41 & 48

A part was replaced the second time under warranty, I don't remember what it was, but there were signs of rat ingress under the hood and they did mention the same to me. Post this, there have been no issues except one due to the carelessness or cluelessness of valet drivers.

The car may have issues, be it EV or ICE, but it is up to the service center to handle it the right way and not escape from taking responsibility.
Hoping the issues on your car get resolved at the earliest.

[WD-42]

Hey, I have an e-Verito. I've faced a very similar problem as you with my car.

Most likely cause is that your Aux battery has failed and is now SHORTING the entire circuit, thus causing a quick discharge of your HV battery.
HV high discharge protection system is kicking in and trying to kick your car into safe mode, however the terrible firmware is probably not catching the errors correctly and tripping everything.

Originally Posted by Nanolover

it might be due to the Exide battery ( aux battery) having a problem ( I am an automotive engineer). My Car's Exide battery had discharged itself TWICE in a span of 4 months and I had to get the local Exide shop to charge/ jumpstart it for me. Trivandrum Motors assures that they will look into it and fix it and will replace the Exide battery if needed.

Breakdown #2---- 15 Jan upon return of car from service center assuring everything is fine

11:00:am -Trivandrum motors returns the car assuring all is fine, software has been updated and no problem with the Exide battery

Looks more likely, considering your Aux has already been completely discharged twice.

My suggestion:

Replace your Aux battery with a new battery and then charge the car overnight to 100%.

My experience:

I had been facing an idle discharge/vampire battery drain of 12-15%. Dash board would sometimes light up like a Christmas tree and car would go into either eco or safe mode.

Took the car to Sireesh Auto Singasandra, Bangalore. They charged me ~2500 and said nothing wrong, we had to update software which we did, you will not face the problem anymore. Came home, no change, still losing 15% every day. Called up Mahindra Sireesh Auto Service Center to ask for an explanation, didn't get one.

Left home one day with 60% charge, went to a supermarket 4 km away. When I returned car went into safe mode. Hard reset it and car went back into normal mode.

Left home with 80% charge, drove to a supermarket 1 km away, when I came back car went into safe mode with HV battery and Aux battery alert. I reset the car (e-Verito has a hard-reset button), the warning lamps were extinguished but the SoC showed 0% while I had left home with 80%. Called Mahindra Service Center (Sireesh Auto, Singasandra), they were beyond useless, the S.A. told me it is Saturday evening 5:40 pm, we are leaving service centre and going home, and offered no solutions or help, and just told me to tow my vehicle home, and to tow it to the service center on Monday morning.

Towed the car home using local tow service because RSA was again useless. I had purchased the car directly from the Mahindra factory (reason for Sireesh Auto's recalcitrant attiude in helping me). Called the factory sales agent, chap was helpful, and explained that he'd seen many cars have this problem, especially ones that had sat idle at the factory or dealer yard for months before dispatch/sale. Please replace aux battery and charge it to 100%, he said. I was a little afraid. My line of thinking is that the car "thinks" it has 0% while in reality HV battery is at 80%, what if the car tries to charge to 100% and overcharges. The agent chap assured me that he's done this multiple times and to try it and that the car once it reaches the real 100% will recognise and reset SoC to 100%.

A good friend of mine works in the EV industry as a battery engineer, so I had a quick chat with him, and his diagnosis was:

• Car either has a short/leak in the wiring harness.
  Friend's opinion was this is the worst-case scenario since it is very hard to diagnose and near impossible to repair unless you rip the whole wiring out of the car and replace.
• HV battery has a dent or physical damage,
  thus losing capacity, can be determined by taking the battery pack out and examining, but smaller dents while hard to find can cause such issues.
• HV battery is failing,
  best case scenario funnily enough, because it is easy to identify and replace.

Our joint conclusion was to tow the car to Mahindra since we didn't know what type of overcharge protection or issue the car had. Called Mahindra's Sireesh Auto again, they said even if I towed the car there, they would just try charging it to 100% as a first try.

Called up my Mahindra agent again. He again reiterated on replacing the aux battery first and said don't bother charging it if you aren't going to install a new aux battery.

So I decided to actually figure out myself what was going wrong.
A 13% drop in a day is equal to a loss of ~1.8kWh of power. Broke out my ammeter and noticed current draw fluctuating between 1 and 8 Amps across the 12v battery.

The big problem is the Aux battery showed 13.6-13.8V when I measured it with a Voltmeter, leading me (and a battery shop guy) to conclude that it was working properly. Under constant load it showed ~12.5V. When I left the voltmeter connected, and tried various loads it would momentarily for less than a split-second drop to ~8-10V, barely noticeable, but all the systems reliant on that would trip, shut down and reset completely.

When I had given the car to Mahindra-Sireesh for service, they too just checked the voltage and said aux battery looks good.

Replaced the battery, and charged the car overnight, car stopped after charging 20%, and SoC reset from 20% to a 100% (original SoC was 80% before it shut down).

Result:

It's been 4 months since I put in a new Aux battery. Having 0 issues. All of my safe mode issues, dashboard Christmas trees, breakdowns all resolved.

Learnings:

Things I learnt while trying to figure out my issue:

1. Most EVs use VRLA-AGM deep discharge batteries for the aux battery, which are normally used for either UPS/Lift UPS/Telecom UPS/Solar-P.V. applications. These aren't your typical SMF-SLA 12V car batteries.
2. EVs (from Teslas to Volvos to Mercs to Mahindras and Tatas) use the Aux battery as a UPS (Uninterrupted Power Supply) to keep the circuits on even when the car is off. See James Mays struggles with his Tesla Model S' Aux battery here:

   https://www.youtube.com/watch?v=NsKwMryKqRE

3. If car hasn't been used for a while, or if the Aux battery is weak, the car will top off/recharge the Aux using the HV battery, thus draining the HV battery.
4. As the Aux battery degrades, either:
   1. the charging current from the HV system just "passes through". The Aux battery effectively is just a big conductor at this point. As to why the chemistry degrades this way I'm yet to learn.
      or
   2. The charging system constantly tries to charge the Aux from the LV and drains the HV.
5. When the car requires a higher current from the Aux which the aux is unable to provide, the car systems that rely on the Aux lose power. If one of those systems is a memory system that keeps current state (drive mode, SoC) etc. that memory is wiped and reset. Thus, the car can go suddenly from 90 or 80 or whatever % SoC to 0.
   
6. A new Aux battery will solve all these issues; however, the new battery will degrade in much the same way as the old one so this is going to be a cycle. I've instead just connected the 12v now to a battery tender to keep it topped up, so it doesn't drain the HV.
7. The main reason for this aux dying seems to be low running or a long break that would've drained the UPS style battery. Apparently on most EVs the aux is recharged by the re-gen. And since it functions as a UPS battery it is continually discharged. However, most batteries including UPS batteries are not designed for continuous discharge, with sparse charging cycles, but deep discharge followed up by immediate charging. Hence my choice to use the battery tender on the 12V aux.

[Nithesh_M]

Is the motor and battery pack on the Tigor EV also of Chinese make like that of Nexon EV?
I was suggesting my father in law to wait for Tiago EV but ever since that pic of Nexon owners battery replacement under warranty I have suggested him to wait for other options.

[Nanolover]

Update: the entire LV wiring harness is being changed. The part has arrived and now work in progress changing it.

Hopefully will receive the car next week.

[jomson13]

@Nanolover - Hope that fixes the problem and you car is back to normal again.

Stupid question - Why does an electric car need an aux battery? Why can't everything just run off the main battery?

[chhotagujju]

Originally Posted by jomson13

@Nanolover - Hope that fixes the problem and you car is back to normal again.

Stupid question - Why does an electric car need an aux battery? Why can't everything just run off the main battery?

Aux Battery in an EV is required to operate your Lights, Wiper, Audio system and Auto lock, unlock. These systems run on a different voltage compared to your main Traction motor.

Also when the main battery gets completely discharged, it is the Aux Battery that still helps you lock or unlock the car.

[Nanolover]

Thankyou all for your well wishes!

Meanwhile, i don't think the problem has been solved by a simple wiring harness change. The car was slow charged yesterday night at the dealer ( from 91 to 100%, i get alert in my app).

Even after 100% charge, the range as per the app is 11 kms, i mean 11 ! See attached app screenshot.

As usual this is what I figured out, no update as usual from the dealer.

Something deeper is yet to come is my guess.