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Old 31st December 2019, 10:23   #241
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Default re: Tata builds a Nexon EV. EDIT: Launched at ₹13.99 lakhs

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Originally Posted by sri_tesla View Post
highway range will be less at higher speeds.
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Originally Posted by sandhyab View Post
EV's mileage can be better in cities than on highways because of regenerative brakes.
Since you gentlemen have gone ahead with this discussion, I have two simple questions to ask:
  • What about the crawling state in city traffic? Induction motors draw really high current at the starting. Now if I am moving at say 15 kph in tight city traffic and have 5 start-stop cycles per km. What about this situation where the regeneration cycle will be extremely short, and every single start cycle will draw a heavy current from battery?
  • What about Mr. AC at the same time? He doesn't generate energy but keep on consistently consuming it - no matter the car is stationary or moving. What about that range part?

I personally know govt. officials who have denied using the Tigor in the city because the car couldn't go even 70 kph in the tight city confines.

Since you guys have decided to talk technology, then it is important to understand how the regen cycle actually works. You can't expect a car to do regenerative wonders while moving at 15 kph or 4.16 meter per second and coming to stop every 200 meters with a stopping distance from 15 kph being 2 meters. And then again the same induction motor drawing a heavy current to start again.

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Originally Posted by pseudo_coder View Post
The highway range can be less than the city range due to difference in speed. High speed causes more air resistance.
I agree with this argument, but here is a catch. While going down the flyovers, going downhill, braking for a toll or some intersection on highway from 100 kph for a decent distance with electromagnetic retardation working at its full potential - this actually gives a proper regeneration, instead of the extremely short regen cycles in the city.

My argument is rather simple, I am talking about the characteristics of the induction motor. In tight city confines, we are not getting any benefit from regen energy because the regen cycles aren't properly and fully applicable there. It's not a train locomotive with empty track ahead - it's a car and mechanical braking which dissipates energy as the heat; still takes the driving seat here.


What I would suggest is, we all can visit the ARAI official website. Get emission reports from there, these reports can provide us some wonderful insights on the Indian Urban, Semi Urban and highway driving cycles. When we have to talk technology and data, let's do that properly gentlemen. What say?

Quote:
Originally Posted by Nav-i-gator View Post
in 1st scenario, car will use approx 10% charge, while in 2nd it would be less than 10% due to regenerative breaking, thus increasing the range.
Not exactly, every single braking is followed by an idle time with some acceleration time again. If braking distance is too short from a slow speed, there is hardly any gain. But during the idle time your AC consumes the battery; and during acceleration time - the in-rush current is huge. Effectively, we need to look at what the gain is how much is lost overall. I see higher loss. What can benefit is lower operating speeds and wind resistance; hence saving more energy.

Last edited by VKumar : 31st December 2019 at 10:42.
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Old 31st December 2019, 10:39   #242
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Originally Posted by pseudo_coder View Post

At some point, car applies brake and comes to a halt (assume braking distance to be 0). The Kinetic Energy, K, is now converted to chemical energy in the battery. The conversion has its losses. Let's assume 10%. So battery capacity is increased by 0.9K. Now, the car has to start from 0 speed and attain the speed of 60 kmph again. So it will use the stored energy from battery. The energy required would be K. But battery has gained only 0.9K. So it has to supply 0.1K more. Now motor also has its losses. Again say 10%. So battery has to supply about 1. 11 K energy for the car to again start cruising at its original speed. Out of this, only 0.9K was provided by regenerative braking. So 0.21K energy is lost by the act of applying brakes.

As a non-technical lay man, this is how I understand it:

Let's take an electric car with 200KM range in a single charge. Starting with a full charge, (1) drive for 20KM on a highway with no breaking and then (2) within city (like Bangalore ) with constant breaking for 20 KM.

in 1st scenario, car will use approx 10% charge, while in 2nd it would be less than 10% due to regenerative breaking, thus increasing the range.
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Old 31st December 2019, 11:30   #243
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Originally Posted by zaks View Post
Regenerative braking doesn't add to much overall in personal automobiles, in electric trains and such it does. It's simply a non-essential selling point.
Regenerative braking plays a big part in eliminating brakepad wear. It allows EVs to have the single pedal driving feature. I never have to touch my brake pedal, I just step off the gas. It is the same with cruise control, regenerative braking is used in the place of brake pads wasting energy in the form of heat.

In terms of range, there can be no definitive answer. What if one is stuck in city crawl in high heat, or freezing cold? One will certainly use up lots of energy in any vehicle, within this city mile.

With my Model3 I find that it is most efficient while cruising at or under 70mph. Anything above 75mph, it consumes a lot more energy.

In city roads with a max speed of 45mph, it is just as efficient as driving at sane freeway speeds. This is contrary to my experience with my Toyota Prius hybrid, which was always lot more efficient in cities than freeway (regardless of speed)
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Old 31st December 2019, 11:54   #244
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Quote:
Originally Posted by Nav-i-gator View Post
As a non-technical lay man, this is how I understand it:

Let's take an electric car with 200KM range in a single charge. Starting with a full charge, (1) drive for 20KM on a highway with no breaking and then (2) within city (like Bangalore ) with constant breaking for 20 KM.

in 1st scenario, car will use approx 10% charge, while in 2nd it would be less than 10% due to regenerative breaking, thus increasing the range.
My point is that in the 2nd scenario, it will use more than 10% charge. Because regenerative braking recovers most of the energy that would otherwise be lost in braking, but on highway, there is no braking. So no energy waste in braking. So nothing to recover.

Regenerative braking is like cashback, albeit a high % one. Two people, A and B, have the same money. A buys a product with 80% cashback. B doesn't buy anything. Now B has more money. B is the highway guy running at 60kmph, and A is the guy using regenerative brakes.
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Old 31st December 2019, 12:09   #245
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Originally Posted by pseudo_coder View Post
My point is that in the 2nd scenario, it will use more than 10% charge. Because regenerative braking recovers most of the energy that would otherwise be lost in braking, but on highway, there is no braking. So no energy waste in braking. So nothing to recover.
.
No emergency braking, but yes/likely yes for regenerative braking. If you have set a speed with cruise control, every time you go down hill, the regenerative braking kicks in. This is usually indicated on the dash of EVs and hybrids.

I said likely yes, because if the set speed is crazy high, energy may be needed even to go downhill to overcome the air resistance. Much depends on the inclination as well.
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Old 31st December 2019, 12:10   #246
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Originally Posted by pseudo_coder View Post
My point is that in the 2nd scenario, it will use more than 10% charge. Because regenerative braking recovers most of the energy that would otherwise be lost in braking, but on highway, there is no braking. So no energy waste in braking. So nothing to recover.

Regenerative braking is like cashback, albeit a high % one. Two people, A and B, have the same money. A buys a product with 80% cashback. B doesn't buy anything. Now B has more money. B is the highway guy running at 60kmph, and A is the guy using regenerative brakes.
How about: Both A & B bought the same product, B at Rs 100 and A at 10% more (Rs 110) but with a 10% cashback (Rs 11). Net spend by A is Rs 99 and by B is Rs 100.
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Old 31st December 2019, 12:28   #247
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Originally Posted by Nav-i-gator View Post
How about: Both A & B bought the same product, B at Rs 100 and A at 10% more (Rs 110) but with a 10% cashback (Rs 11). Net spend by A is Rs 99 and by B is Rs 100.
The product here is braking, and we are saying that highway run is at constant speed without brakes. So no, B didn't buy the product.

Quote:
Originally Posted by GutsyGibbon View Post
No emergency braking, but yes/likely yes for regenerative braking. If you have set a speed with cruise control, every time you go down hill, the regenerative braking kicks in. This is usually indicated on the dash of EVs and hybrids.

I said likely yes, because if the set speed is crazy high, energy may be needed even to go downhill to overcome the air resistance. Much depends on the inclination as well.
I am talking about flat road. Going downhill is a different case, and must be accompanied by same uphill distance for a fair comparison.

Last edited by Chetan_Rao : 31st December 2019 at 17:56. Reason: Merged back to back posts.
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Old 31st December 2019, 12:34   #248
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Originally Posted by pseudo_coder View Post
The product here is braking, and we are saying that highway run is at constant speed without brakes. So no, B didn't buy the product.
I'm sorry, but the product is range. And what we are discussing is what effect (regenerative) braking has on it, in isolation. So yes, breaking is like cashback gained on battery usage in both scenarios
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Old 31st December 2019, 16:50   #249
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Originally Posted by VKumar View Post
Not exactly, every single braking is followed by an idle time with some acceleration time again. If braking distance is too short from a slow speed, there is hardly any gain. But during the idle time your AC consumes the battery; and during acceleration time - the in-rush current is huge. Effectively, we need to look at what the gain is how much is lost overall. I see higher loss. What can benefit is lower operating speeds and wind resistance; hence saving more energy.

you are absolutely correct, and in Delhi/Bangalore level of peak traffic, regenerative braking I would expect to be useless. Once we have multiple EV cars around maybe we will pick this topic up from our experiences.


Quote:
Originally Posted by pseudo_coder View Post
My point is that in the 2nd scenario, it will use more than 10% charge. Because regenerative braking recovers most of the energy that would otherwise be lost in braking, but on highway, there is no braking. So no energy waste in braking. So nothing to recover.

Regenerative braking is like cashback, albeit a high % one. Two people, A and B, have the same money. A buys a product with 80% cashback. B doesn't buy anything. Now B has more money. B is the highway guy running at 60kmph, and A is the guy using regenerative brakes.

There is absolutely no point in having a debate here and the analogy used is crap, please go ahead and read about the technology (in detail) before starting an argument. Above gentleman has read about the technology (I assume) and understands its limitation. With you, you have not understood the technology nor have you paid any attention to the 1000's of reviews/feedback of actual users from actual EV cars. Regenerative braking in ideal condition (based on factors like driving conditions, terrain and the efficiency of the technology of regenerative brakes) is generating electricity by converting Kinetic energy to chemical/electrical energy, and losses are infact to the tune of 30-40%.
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Old 31st December 2019, 17:54   #250
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Note from Support:

Please keep the discussion civil, and stick to the thread topic. A detailed discussion on regenerative braking principles and technologies can be done in a separate thread.
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Old 1st January 2020, 17:27   #251
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Quote:
Originally Posted by pseudo_coder View Post
(assume braking distance to be 0).
Cannot move forward with this calculation if braking distance is Zero. There's absolutely no energy recovered with this assumption. During normal operation, electrical energy from battery is converted to rotary motion of the motor/wheel. During Regen, the rotation of the wheel/motor is converted to electrical energy. So If we assume braking distance is Zero, there is no energy recovered

But let us still continue for the sake and take your own calculation...
Quote:
At some point, car applies brake and comes to a halt (assume braking distance to be 0). The Kinetic Energy, K, is now converted to chemical energy in the battery. The conversion has its losses. Let's assume 10%. So battery capacity is increased by 0.9K. Now, the car has to start from 0 speed and attain the speed of 60 kmph again. So it will use the stored energy from battery. The energy required would be K. But battery has gained only 0.9K. So it has to supply 0.1K more. Now motor also has its losses. Again say 10%. So battery has to supply about 1. 11 K energy for the car to again start cruising at its original speed. Out of this, only 0.9K was provided by regenerative braking. So 0.21K energy is lost by the act of applying brakes.
If there was no regen, to go back to the original cruising speed, battery has to supply 1.11K which would reduce the range? Now that 0.9K that was regenerated back to the battery will increase the range won't it? it's not that that without regen, you wouldn't have braked at all.

Quote:
My point is, if you go the same distance uphill and downhill, you will end up losing range, not gaining it.
The below quoted post is from my Travelogue to Mysuru on my Ather 450. I've selected the part where I went up the Chamundi Hill from the base and came back down to the "same point". It is 'almost' the same distance (the downward journey was a little shorter due to a small difference in upward and downward routes)

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Originally Posted by hemanth.anand View Post
[b]
First stop: Chamundi Betta. Chamundi is the royal deity of the Mysore Kingdom and the temple is located on top of the hill overlooking the city by 11:00, we were at the foothills. The base of the hills is at around 600m above MSL and the 7 Kms distance road to the top takes us to a height of around 1200m above MSL.

With a small stop of 5 minutes mid-way for some pictures, we reached the top of the hill in 20 minutes. The scooter had consumed 15% of battery for the climb and the range dropped by 10kms....

…from here the road gets really steep and the scooter was on Regen throughout. By the time I got down, The scooter had gained 2% charge and 1km of range during the downward ride of 6kms. So all in all the ride 13kms drive up and down took 13% of battery
I reached the base of the hill with 53kms range left.
when I reached the top, 43kms range was remaining.
When I came back down, 44kms range was remaining.
For a drop of 9kms range, I had actually covered 13kms.

Even for such a small distance of 6 kms up and down "I have gained" 4kms range. So Regen does give you additional range
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Old 1st January 2020, 18:07   #252
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Originally Posted by hemanth.anand View Post
it's not that that without regen, you wouldn't have braked at all.
I think this clears the air. The discussion started with comparing highway range with city range, assuming we use brakes multiple times in the city and never on the highway.

Of course, compared to using conventional braking, regen brakes add to the range. But the point was whether a car with regen braking, like Nexon EV, gives better range in city or on highway. My point is, for an EV,

No braking > braking with regen brakes > braking with conventional brakes.
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Old 1st January 2020, 18:41   #253
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Originally Posted by pseudo_coder View Post
Of course, compared to using conventional braking, regen brakes add to the range. But the point was whether a car with regen braking, like Nexon EV, gives better range in city or on highway. My point is, for an EV,

No braking > braking with regen brakes > braking with conventional brakes.
In the E2O I had, the regen used to add about 1-2Kms of range within the citt limits. On the occasional trip on NICE road, I have driven 21KMs with range decreasing by just 15KMs. So with careful driving, regen can extend the range. I have driven my 80KM range E2O for over 92KMs for 93% battery consumption and this was with AC.

There are examples of people driving to Mysore from Bangalore in their E2O plus which had a 140KMs range while the distance between the two cities is 150KMs.
This is in an EV which is restricted to a speed of 80KMPH.

The new gen EVs can reach higher speeds and coasting from such speeds can add to the range.
For example, during my test drive of Kona, the car recovered a range of 0.35Kms when the car decelerated from a speed of 80KMPH to 35KMPH in level 3 regen setting. The number was lower in level 2 and level 1 regen.
With careful driving, regen definitely will aid in increasing the range of the car.

Also there are examples of people driving to Mangalore and Pondicherry from Bangalore in their Konas where the distances are more than 300KMs which is also certified for a range of 300Kms according to the manufacturer.
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Old 1st January 2020, 20:06   #254
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Maximum Regen happens when we ease off the accelerator and cruise to a stop rather than abrupt braking.It is also called as a pulse and glide technique which I have experienced in my Gen2 Toyota Prius to maximize mileage.
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Old 1st January 2020, 20:37   #255
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Originally Posted by Blooming Flower View Post
Before we close the loop and the discussion related to the gradeability-- what about the trails and vehicles used in Moab for OTR? Don't they abide by this law? Just curious to know.
What I wrote was for an Ideal road car and road tyres. The OTR vehicles in Moab trails for example can do it with the help of many additional factors like...
1. A little headstart. (Restart gradient mentioned in the brochure is tested with 1mtr of space between the rear of the vehicle and the end of the gradient)
2. lower centre of gravity
3. centre of gravity between the wheelbase of the vehicle(which is very important from keeping the vehicle from tipping over)
4. Tyres with higher grip
5. Higher friction of coefficient of the rock surface
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