[spgv]

Originally Posted by Palio_2005

Hi,

Pardon me for an absolute noob question. Mods please delete or merge the thread is not relevant. The question I had is why is it not possible to generate electricity when the EV is in motion? Can’t the kinetic energy of the motion of wheels be converted to electric and recharge the battery?

That will be a Prepetual Motion Machine:

PMM1: Produces work without input of energy.(Violates law of thermodynamics)

PMM3: One that completely eliminates friction and other dissipative forces, to maintain motion forever due to its mass inertia.

Then the law of entropy: Entropy will always increase.
Therefore when IC engine converts chemical energy to kinetic, heat is dumped to the environment (increasing entropy). The engine harnesses a small percentage of this increasing entropy and converts it to Kinetic energy(Effeciency of engine).

With the physics refresher out of the way, getting back to the query.

Vehicle moves and to overcome the friction a lot of energy is lost.(To assume lossless motion, that's PMM-3, if it ever existed would not incur any loss)

Generator on the vehicle converts kinetic energy to electrical and motor converts electrical energy back to kinetic (That's PMM-1). There are losses at every step, that is conversion of mechanical to electrical energy & electrical to mechanical. (Remeber the law of entropy)

"Oh ye seekers after perpetual motion, how many vain chimeras have you pursued? Go and take your place with the alchemists."

— Leonardo da Vinci


Source: The internet

[shamanths3]

Originally Posted by ritesh_44

There is a reverse resistance in the motor due to the current being generated by moving wheels, the motor itself doesn't try to rotate in reverse. The resistance is due to backward current generated by moving wheels. Its like a dynamo where external force (to rotate) is required, here the wheels provide that force and slows down in the process.

Thanks a lot. Any idea how Multi level regen works? How are they able to control the resistance to adjust the rate at which the car slows down?

[Pedalmasher_20]

I have one silly doubt about this regen braking. Having read this thread extensively, an idea stuck in my mind. "Why not use the regenerative braking as a whole and sole source for stopping our car". By this, what I meant is, upon pressing the brake pedal, regenerative braking in the car gets activated in such a way that the intensity of the regen braking is directly proportional to the amount of pedal pressed. So in that way, we can stop our cars in normal fashion instead of letting of the accelerator way before the stopping point, gain few kms in the range, as well as eliminating the maintenance cost related to disc pads as they won't be needed anymore. Is this possible? If not, pls explain...


Regards,
Pedalmasher_20

[Cresterk]

Man this whole thread reminds me of this old meme we had circulating in our school whatsapp groups.

[anandjm]

Originally Posted by Pedalmasher_20

I have one silly doubt about this regen braking. Having read this thread extensively, an idea stuck in my mind. "Why not use the regenerative braking as a whole and sole source for stopping our car". By this, what I meant is, upon pressing the brake pedal, regenerative braking in the car gets activated in such a way that the intensity of the regen braking is directly proportional to the amount of pedal pressed. So in that way, we can stop our cars in normal fashion instead of letting of the accelerator way before the stopping point, gain few kms in the range, as well as eliminating the maintenance cost related to disc pads as they won't be needed anymore. Is this possible? If not, pls explain...

There's a limit to what regen braking can do. It's more effective at higher speeds and less effective at lower speeds. So you do need to use mechanical braking at some point.

[mohanphadnis]

Originally Posted by Pedalmasher_20

I have one silly doubt about this regen braking. Having read this thread extensively, an idea stuck in my mind. "Why not use the regenerative braking as a whole and sole source for stopping our car". By this, what I meant is, upon pressing the brake pedal, regenerative braking in the car gets activated in such a way that the intensity of the regen braking is directly proportional to the amount of pedal pressed. So in that way, we can stop our cars in normal fashion instead of letting of the accelerator way before the stopping point, gain few kms in the range, as well as eliminating the maintenance cost related to disc pads as they won't be needed anymore. Is this possible? If not, pls explain...


Regards,
Pedalmasher_20

Hardly ever use that brake pedal on my kona, 99% of the braking is achieved using regen. But regen braking is not as strong as just using a pair of calipers to stop the wheel from rotating.

[Pedalmasher_20]

Originally Posted by anandjm

There's a limit to what regen braking can do. It's more effective at higher speeds and less effective at lower speeds. So you do need to use mechanical braking at some point.

Originally Posted by mohanphadnis

Hardly ever use that brake pedal on my kona, 99% of the braking is achieved using regen. But regen braking is not as strong as just using a pair of calipers to stop the wheel from rotating.

Can't the regen be made stronger? Strong enough as the brakes... I think, we just have to increase the level of resistance that the motor produces to increase the regen braking, right?

[SKC-auto]

Originally Posted by Pedalmasher_20

Can't the regen be made stronger? Strong enough as the brakes... I think, we just have to increase the level of resistance that the motor produces to increase the regen braking, right?

Some EVs already have on demand regen, when you slightly press the brake pedal, the regen increases.

But you should not depend 100% on the regen, what if you need to get emergency braking, there is a limitation to regen braking, it depends on motor capacity and batteries ability to take such high power.

Also, if your mechanical brakes are used less, they tend to rust, which will cause problems during any emergency braking.

[fordday]

Originally Posted by SKC-auto

there is a limitation to regen braking, it depends on motor capacity and batteries ability to take such high power.

This is the reason why we cannot have regen as the only braking device. Even if the motor (which acts as generator during regen) produces enough current the batteries cannot consume it that fast.

An alternative here is to dissipate the extra current as heat though an electrical resistance, like in locomotives. But this means same as physical braking, as the energy is wasted in both the cases.

Moreover the regen decreases as speed decreases, so in most cases the physical brake is needed to completely stop the car while nearing zero speed.

[T-Bone]

I too had a similar question popping up in my mind but in a different way.

Why don't they include both, One motor and One generator with a split battery pack?

What am I achieving?

Well, the motor helps EV in propulsion while at the same time the generator recharges ONE OF THE split battery packs.

Using electronics, we can switch between the battery packs depending of the SoC in each pack.

[SKC-auto]

Originally Posted by T-Bone

Well, the motor helps EV in propulsion while at the same time the generator recharges ONE OF THE split battery packs.

And run the car without charging for ever?

Simple question, why do you get lower fuel effeciency when you turn on AC in your car? Why most cars lose power when the AC is turned ON? Why some people turn off AC when a quick overtake is needed or on ghats?

Generating Energy needs Energy from your car itself. Imagine the additional load required to charge the secondary battery on the primary battery.

There is no free money & free Energy.

[mohanphadnis]

Originally Posted by Pedalmasher_20

Can't the regen be made stronger? Strong enough as the brakes... I think, we just have to increase the level of resistance that the motor produces to increase the regen braking, right?

For Gen 3 Formula E cars :-
"It also gets a second motor on the front axle for the first time, capable of a peak 250 kW to go with the rear motor's peak 350 kW. Interestingly, this is much more about stopping than acceleration. Under hard braking, the powertrain's full 600 kW (805 hp) will be accessible, giving the Gen3 car more than twice the regenerative braking capacity of its forebears. The e-brake will be so strong that these cars won't even run hydraulic brakes on the rear wheels, and the FIA projects that a staggering 40 percent of the total power used in races will come from the regen system."

So we are getting there. I dont know if removing all four brakes would be possible though.

[T-Bone]

Originally Posted by SKC-auto

And run the car without charging for ever?

Simple question, why do you get lower fuel effeciency when you turn on AC in your car? Why most cars lose power when the AC is turned ON? Why some people turn off AC when a quick overtake is needed or on ghats?

Generating Energy needs Energy from your car itself. Imagine the additional load required to charge the secondary battery on the primary battery.

There is no free money & free Energy.

But does that stop you from using the AC? We all still use it right ?

Anyways, at the end of the day battery pack size determines the range (one of the factors) so for the sake of argument, let's take a 20kwh battery pack and just divide it into two (split) 10kw + 10kw. So use one 10kw pack while the other charges and switch the pack as needed. FYI, I have seen low rmp high voltage/current generators. Fix one (just an alternator) and use it to charge the battery pack. I'm sure we can achieve that with advancement in tech.

[Geta]

Too much of nicety and delving into hypothetical situations for the sake of political correctness has diluted the whole point everyone was trying to make from the beginning in this thread to the extent that the original question gets repeated after all the discussion.

I think this situation is best explained using Lenz's law (Induced current is always opposed by the cause that produces it. Meaning in a Dynamo, one has to overcome a certain amount of resistance using mechanical energy to generate electrical enegy). Hence using the wheels of an automobile as a Dynamo is practically useless (Exception: regen braking when the vehicle has to decelerate) as the energy generated will be less than the energy spent.

Anything more than this (if at all; very unlikely as it is against the laws of physics. We can only fine tune a little bit here or there but not much scope to play around), is going to be intellectual property and will never be discussed openly by the inventor(s) in a public forum.

[SKC-auto]

Originally Posted by T-Bone

I'm sure we can achieve that with advancement in tech.

Sorry, no amount of advancement in tech can create energy(basic laws of physics), it can only be converted from one form to another, from your primary battery(10kwh) to the secondary battery(10kwh) after all the losses in the conversion.