[Neversaygbye]

Originally Posted by IshaanIan

Why did the left side headlamps require replacement in the first place?

They needed to be replaced because of an accident is what is mentioned in an earlier post.

[Jeroen]

Originally Posted by chandu

A short in an automotive circuit can easily result in a current of 100A or more drawn from the battery, no fuse should be rated so high. Typically these fuse ratings are carefully calculated so that any unnecessary current load should blow the fuse.
We make parts for automotive electrical systems and there is no way a failure analysis like this would ever be accepted by an OEM.

I was simply responding to some members believing that fuses should prevent this from happening. You are in the automotive industry, so you know what I am talking about.

A poorly executed modification, say too thin wire, might mean that wire will heat up, long before the fuse pops. If you have a 15 Amp fuse in a 12 V circuit that means you can generate 180Watts of energy. Have you ever tried holding a 40w bulb after it has been switched on for more than half a minute.

If somebody made a modification and used half the gauge wire as the original what do you think would happen. The circuit would not draw any more current, but that piece of thin wire would heat up real quick!

The same is true for a wire being chaffed and causing a ground. It might not be enough to cause the fuse to pop. But it will certainly heat up things!

Same agin, if a wire got pinched in between two parts.

I would also like to draw attention to the many, many test that have been carried out on automotive fuses over the years. They don’t pop very precisely do they? In fact, most pop at a higher value than their rating. To some extend this can be explained that it is not unusual to have more than 12V in some circuits.

Very few fuses pop at lower than the stated value. The one thing everybody around the world seems to agree on, is that as a rule of thumb, always buy the most expensive fuses you can get. The cheap ones, are extremely unreliable and will almost always pop at way too high values!

Now, I don’t say I agree with the conclusion of the dealer. They have shown no evidence at all. Going by many threads and even many more posts on TeamBHP I would say it is fair to say that aftermarket electrical work on cars in India is not necessarily up to Industry standards.

Again, that does not make the explanation any more credible, just statistically more likely. I must admit, if they HD shown evidence I a quite sure some of our members would have responded that the evidence was fabricated.

So, I am not saying anything about the root cause as such. Just a few words and thought about what you can and can not expect from fuses.

This is coming from guy who ended up with two melted wall mounted sockets in his apartment in Delhi and no popped/tripped fuses either!

As you are in the electrical automotive industry I would really like to understand how you guys design and test fuses and what tolerance and repeatabillity you allow for?
Jeroen

[ASP007]

As seen from the pictures, the fire broke out or predominantly was behind the repaired left headlight. A shoddy job combined with parts not up to OEM standard definitely caused it. Since the vehicle was repaired elsewhere, the owner should have taken it to the Tata service center to ensure the quality of work done. This is a good reminder for everyone and hope the insurer will do some investigation on the repair shop and remove it from their list. At least some folks (read car owners) will be spared if they take such an action.

[Joeboy]

Vehicle manufacturers always have the habit of washing their hands if in case there is an issue with the vehicle and when the work is done in an unauthorised workshop. All the manufacturers state in the owners manual that if any kind of repair work is done in an unauthorised workshop then the warranty would be void. So it is no surprise regarding the statement that Tata Motors has released regarding this fire incident. There was also an incident of Nexon catching fire last year. Tata Motors has said at that time that there are probing the incident but so far are yet to release their findings on that fire incident which may lead us to believe that they have hushed it up.

[subuiyer]

A fuse is not necessarily an all-scenario fail-safe. There can be instances where lot of amps can pass through without breaking the circuit.

Unfortunately, there are too many possible scenarios. Aftermarket additions/changes always carry an element of this risk. Let me add, so do insufficiently tested products from OEMs. Given the size and commercial value of our auto market, perhaps it's time an NTSB equivalent organization for thorough investigations is put in place in India (pardon my ignorance if one already exists).

Perhaps anecdotal, but I have witnessed projector LED lamps matching permissible legal ratings causing the plastic casing around it to smolder within mins of turning ON due to unscientific fitting.

[abc_xyz]

Originally Posted by Joeboy

There was also an incident of Nexon catching fire last year. Tata Motors has said at that time that there are probing the incident but so far are yet to release their findings on that fire incident which may lead us to believe that they have hushed it up.

I was also wondering about the same thing. Why did Tata not release any report for the 1st fire incident?

[UD17]

Originally Posted by Venkatesh

Tata Motors statement in recent Nexon EV fire.

Attachment 2441839

Very tactfully they have replaced the FIRE word with THERMAL Incident. That itself shows the true intent of this press release or analysis.

Rather than conducting a thorough analysis, they choose the easy way to find that the vehicle got repaired outside and to conclude that as the absolute reason of Fire. IMHO, its a difficult situation for analysis for any company when vehicle is totally gutted by fire but Tata Motors concluded that quite fast.

This could be due to external repairs, but we expect a better analysis and honesty from TML for these high severity cases.

[Jaggu]

Would be interesting to know what the owner has to say and how this matter was settled with them? Also more details of so called mod?

[nishsingh]

Originally Posted by chandu

Does this not sound like a bogus analysis?

Even if a head lamp short circuited and caused an excess current flow leading to over heating and fire, a correctly rated fuse should have opened up and stopped the flow of current into the affected node.

Originally Posted by padmrajravi

Most workshops that replace headlamps with high-power ones, mess with the fuses too.

Unfortunately, this is precisely what a neighborhood garage did on my headlamp - he didn't have the 30 Amp fuse that was required. So he used a copper wire instead : Frustrati

[ashokabs]

I read through the whole thread. Interesting that most people do not believe that any car company in India would do an honest investigation and report correctly. Most believe that the company will lie through their teeth. That is a sad state of affairs. The auto industry has matured over the years thanks to competition. Tata's are usually trusted more than many other car manufacturers. I am not commenting on this incident at all but on the negative comments about the manufacturer. It would appear from the location of the fire and the events leading up to it that shoddy workmanship could be the most likely cause. It is a timely reminder to go to authorised workshops or known reliable ones for all repairs - not just electrical repairs.

In the old days I remember similar situations in car dynamos and voltage and current regulators. The mechanics would fiddle with the settings of the regulator which could easily result in fires. I had to train some local electricians to do the current and voltage setting of the regulators!!

[aim120]

Originally Posted by chandu

Does this not sound like a bogus analysis?
A well designed electrical system will have a fail safe fuse or circuit breaker that should protect the system from a malfunctioning node that has failed with a short circuit.
Even if a head lamp short circuited and caused an excess current flow leading to over heating and fire, a correctly rated fuse should have opened up and stopped the flow of current into the affected node.

My house has all safety stuff from the meter ceramic fuse, surge protectors, wifi RCBO, voltage cut off devices, over spec wires, MOVs and yet there was a arc in distribution board which was hot enough to melt the bus bar holder. None of the devices failed to protect.

Why did arcing happen, its because of loose contact. How did the screws become loose, well when you have multiple trucks filled with sub woofer and speakers during some festival procession, it causes so much vibration that screws in busbar loosen them selves.

The point is a correct fuse (circuit breaker is just a modern version of the fuse) and even a higher rated wires will only protect you from over current and not arcing. Arcing is hot enough to melt steel.

In DC arcing is twice as big vs AC. So loose contact due to slicing wires and using insulation tape on a poorly joint wires are potential for fire hazards. Using low quality led lamps that heat up a lot, will not blow a fuse or trip any circuit breaker in the car.

The led or any accessory should itself have a thermistor to sense heat and cut off or have fuse in the pcb of the led.

[Yusha]

Originally Posted by Jaggu

Would be interesting to know what the owner has to say and how this matter was settled with them? Also more details of so called mod?

It is mentioned in a post above. The car was in an accident and the headlamp and some wiring was replaced and the owner has no idea about the electrical work done on the car.

[chandu]

Hello Jeroen,
Thanks for the long and interesting reply. There are a lot of questions and I will try and answer all of them. This is going to be long and might be a bit technical.

Originally Posted by Jeroen

I was simply responding to some members believing that fuses should prevent this from happening. You are in the automotive industry, so you know what I am talking about.

Yes, fuses can prevent this sort of thing from happening and that is exactly why fuses of so many different ratings can be found in one fuse box of any vehicle.

Originally Posted by Jeroen

A poorly executed modification, say too thin wire, might mean that wire will heat up, long before the fuse pops. If you have a 15 Amp fuse in a 12 V circuit that means you can generate 180Watts of energy. Have you ever tried holding a 40w bulb after it has been switched on for more than half a minute.

Yes, this is true, however, copper wires have very low resistance and will not heat up very much even with a fairly high current, for example, a 16AGW copper wire will have a resistance of approx 20mOhm/meter and as we know, Power=I^2xR, so even if 100 Amps (short circuit current) is flowing in a 16AWG cable of 10cm length, the total power dissipated = 20W which is not enough to heat up the wire enough to burn through its insulation. A fuse, for example, will not be made of pure copper, it will be made of an alloy that has defined fusing characteristics and will be made of a specific cross section that will be calculated to melt when a certain power is dissipated in the link. There are standards that are available for fuse designs that will specify the fusing characteristics of each fuse. A fuse manufacturer will publish a Time Vs Amps chart for their fuses which will tell us how long will a fuse open for a certain over current, a min and max time is specified clearly for each fuse rating. One point that is usually important is that they all have a requirement that in case of a short circuit condition, the fuse must blow without damaging its socket and its surroundings.

Originally Posted by Jeroen

If somebody made a modification and used half the gauge wire as the original what do you think would happen. The circuit would not draw any more current, but that piece of thin wire would heat up real quick!

As above, not much would happen if a thinner wire was used, yes, it would be hotter than before but not by much. Certainly not enough to cause a fire.

Originally Posted by Jeroen

The same is true for a wire being chaffed and causing a ground. It might not be enough to cause the fuse to pop. But it will certainly heat up things!
Same agin, if a wire got pinched in between two parts.

Yes, this is true, but, I don't think that it would become hot enough to catch fire. However, if it does get grounded, then a short can happen causing a very large current to flow. but, if the ground is happening in a way that it causes an intermittent short or just sparking, it will not draw a lot of current continuously.

Originally Posted by Jeroen

I would also like to draw attention to the many, many test that have been carried out on automotive fuses over the years. They don’t pop very precisely do they? In fact, most pop at a higher value than their rating. To some extend this can be explained that it is not unusual to have more than 12V in some circuits.
Very few fuses pop at lower than the stated value. The one thing everybody around the world seems to agree on, is that as a rule of thumb, always buy the most expensive fuses you can get. The cheap ones, are extremely unreliable and will almost always pop at way too high values!

I would encourage you have a look at the fusing charts by one of the biggest fuse manufacturer Little Fuse.
https://www.littelfuse.com/products/...fuses/ato.aspx
Again, a fuse will not and should not open at the rated current, it is designed to carry the rated current indefinitely. It will only fuse when the rated current is exceeded by a fair margin.

Originally Posted by Jeroen

Now, I don’t say I agree with the conclusion of the dealer. They have shown no evidence at all. Going by many threads and even many more posts on TeamBHP I would say it is fair to say that aftermarket electrical work on cars in India is not necessarily up to Industry standards.
Again, that does not make the explanation any more credible, just statistically more likely. I must admit, if they HD shown evidence I a quite sure some of our members would have responded that the evidence was fabricated.
So, I am not saying anything about the root cause as such. Just a few words and thought about what you can and can not expect from fuses.
This is coming from guy who ended up with two melted wall mounted sockets in his apartment in Delhi and no popped/tripped fuses either!
As you are in the electrical automotive industry I would really like to understand how you guys design and test fuses and what tolerance and repeatabillity you allow for?
Jeroen

As far as design of the electrical system goes.... every manufacturer will do a design FMEA and a process FMEA to determine where failures can occur and how to mitigate these. If it was possible to have a failure due to a short circuit, then they would ensure that a protection would be available to break the circuit.
Now, as far as burning, a manufacturer would normally use a fire retardant or even a fire resistant material (plastic) at locations where there could be a chance of fire occurring.
As far as tolerances go, every certified and approved fuse manufacturer, will sample test each batch to make sure that the fusing characteristics are as per the data sheet. Maybe there are fly by night manufacturers who skip such quality checks but any reputed automotive manufacturer will not take such risks.
As far as your experience of melting sockets in Delhi, I would think that someone installed copper wires in your fuse socket (pretty common occurrence in India) when a fuse opened up and the right gauge of fuse wire was not available, this is more common than you would think. Unscrupulous electricians do this all the time. Thankfully this is becoming less common now due to the use of MCB's on the fuse boards. There are also a lot of poor quality plugs and sockets over here and this kind of problem is not uncommon. A lot of builders cut corners in these items.
Another thing repair men do often is to just twist together wires and wrap them with insulation tape, rather than use a connector or even solder wires and then insulate them, this can easily cause problems down the line.

My point was that the press release at minimum sounded like they were putting the blame somewhere easy and not going deeper.

[steadfast]

1. Images show fire localised to left headlight region.
2. Owners story tells that car had an accident in which left headlight side was repaired and insurance company forced owner to repair outside authorised service centre for cashless.
3. Tata gives an explanation which looks authentic as a genuine consequence of statement 1 and 2 above.

Case closed. What else are people expecting from Tata ? Or are we Indians uncomfortable when a case is concluded so soon versus thousands of pending cases since long.

Just move on people.

[chandu]

Originally Posted by aim120

My house has all safety stuff from the meter ceramic fuse, surge protectors, wifi RCBO, voltage cut off devices, over spec wires, MOVs and yet there was a arc in distribution board which was hot enough to melt the bus bar holder. None of the devices failed to protect.
Why did arcing happen, its because of loose contact. How did the screws become loose, well when you have multiple trucks filled with sub woofer and speakers during some festival procession, it causes so much vibration that screws in busbar loosen them selves.
The point is a correct fuse (circuit breaker is just a modern version of the fuse) and even a higher rated wires will only protect you from over current and not arcing. Arcing is hot enough to melt steel.
In DC arcing is twice as big vs AC. So loose contact due to slicing wires and using insulation tape on a poorly joint wires are potential for fire hazards. Using low quality led lamps that heat up a lot, will not blow a fuse or trip any circuit breaker in the car.
The led or any accessory should itself have a thermistor to sense heat and cut off or have fuse in the pcb of the led.

1. Most likely, the MCB will be after the bus bars, so they will not trip for a fault on the bus bar. Plus, the arc will not necessarily result in a higher current draw in a bus bar.
2. The nuts likely got loose as the installers did not put any anti vibration washers like a spring or star washer.
3. Yes, loose contacts can cause arcing failures, this can happen easily and will not be prevented by a fuse or an MCB.
4. Yes, DC arcs are difficult to extinguish as compared to AC arcs. This is why fuses used for DC applications are designed for DC use. Switches specifically designed for DC have wider clearances.
5. Lastly thermistor or over temp protection being part of the LED design, is a different issue. It will be nice to have. Most small motors have auto reset thermal switches that will cut off power when a set temp is exceeded and will reset when the temp is normal again.