Charging while driving

Charging while driving

I will be the first to admit that I have no clue what I am talking about here so don't yell at me if this is a stupid question.

I know Tesla recently came out with the dual electric motor setup but before they did that I was thinking about the fact that all that rotational energy from the front wheels was essentially being wasted. Would it be possible to, instead of putting a motor in the front, put a generator in the front or run the front motor in reverse all the time so that as you drive you are drawing energy to power the rear motor but simultaneously using the front wheels' motion to generate electricity to recharge the battery. I realize that is basically what you are doing with regen braking, but my question is could you have it do that all the time? Or do the laws of physics just go NO and then proceed to give you a dope slap for even suggesting such nonsense?

Rocky_H | November 4, 2014

The irritation was building, but thank you for being open to the answer there at the end. Yes, that would be a violation of laws of physics and conservation of energy.

Generators don't spin freely with no effort. To generate electricity with them, they have some resistance to turning--it takes force to spin them around. In the application you are talking about, you can't just add a generator and not affect the motion of the car. The generator would slow the car down, or would require you to press the accelerator down harder, using more energy, just to keep up your speed. That is exactly why they use it for regenerative braking--generating any electricity with it slows the car.

Remember that motors/generators just convert energy from electrical to kinetic or vice versa. The idea you are proposing is some conversions in a closed loop. Battery - motor - car motion - generator - battery. Motors and generators are at best a bit over 90% efficient, so any extra energy that you pull from the battery to put into car motion and then try to grab it back to put back in the battery is getting converted twice, and you lose about 10% each time, so the system would be running itself down just from that, not even considering wind resistance, tire friction, etc.

So yeah, that's been thought of, but it is called a perpetual motion machine, and it provably cannot exist.

ian | November 4, 2014

Yup. Your last sentence is spot on.

Timo | November 4, 2014

. I realize that is basically what you are doing with regen braking, but my question is could you have it do that all the time?

You obviously could do regen while driving just like you can brake while driving, but doing that you would lose a lot more than you gain. You just deplete your battery faster.

We can't create energy, nor can we destroy it. We can only convert it to different forms. No conversion is ever perfect, so in each conversion you lose some to non-usable forms of energy.

elephant in a bottle | November 4, 2014

Nothing impossible really .. You will need a car "organism" to do "regen" by letting it feed while it's moving .. sounds like a camel ride :)

EmperorTytus | November 4, 2014

On the other hand, if you supercooled the magnets driving the front motor enough to approach zero rotational friction, you could recover nearly all of the energy imparted by the rear motor. This would allow for hundreds of additional miles . . . Omg, someone tell Tesla!

lph | November 4, 2014

A lot of people here are without proper education in basic physics. Timo is correct.
A generator is simply a means of converting kinetic energy (energy from movement) to electrical energy which we then usually store in a battery. The process gives off heat (energy) due to friction of bearings etc mostly but other forms as well which results in loss of storable / usable energy during that process. All else being equal the fewer energy covertion steps we have the higher the efficiency of the whole system. No cheating is allowed or will work. This is the result of the law of entropy.
Therefore this process cannot be even be100% efficient, let alone gain energy from nowhere. This is a zero sum process and some energy always leaks away leaving you with less total usable energy to use than you put in.
If you want more energy you have to grab it from outside of this local system.

Brian H | November 5, 2014

No, it wouldn't. It would allow exactly the miles you get now, minus the penalty of every extra conversion loss you introduced. You can't win. You can't break even. You can't leave the game.

joenanp | November 5, 2014

Now if there were a solar panel on the roof of the car.............

BrassGuy | November 5, 2014

Solar panel on the roof, what a great idea! Then you could use the premium interior LED lights without worrying about range! Only during the day though.

Red Sage ca us | November 5, 2014

This would create a perpetual stopping machine.

Timo | November 6, 2014

Solar panel onto roof, and each street light replaced with 40kW laser that shoots to that solar panel when car goes by.

That would work, but you have to hope that their aim is perfect every single time.

al | November 7, 2014

Just waiting for "inductive" powered..My question is...what is the operating voltage of the Tesla battery ? solar panels are limited...say 44vdc...
...following Danfos Turbo cor....magnetic bearings...a small trailer...could hold a small generator...charging on the GO...Has anyone put a trailer hitch on a Tesla...In case you are in a prolonged power outage and need to get out of cowboy

DTsea | November 7, 2014

If a charge handle is plugged in the car will not move.

So no the car is not set up to run off an auxiliary ....power....unit.....

draconious_z | November 9, 2014

Is this usually when someone mentions putting a "sterling engine" on the battery and motor to capture the heat energy? or maybe a power pot?

:) lol.............

DTsea | November 9, 2014

Well since the battery only gets to about 30C ta thermoelectric generator won't do anything.

kittykittybangb... | November 10, 2014

Your last phrase is identify on.

Brian H | November 10, 2014

Yours isn't.

DTsea | November 11, 2014



hpjtv | November 15, 2014

@EmperorTytus it takes energy to cool things. Your freezer doesn't miraculously cool its contents if not plugged in (unless it is super cold outside already and the door is open).

vgarbutt | November 16, 2014

The only thing that gets charged while driving is the driver! Oh and your devices, maybe a cordless shaver which you can use on the highway in autopilot mode!

StarVenture | November 21, 2014

Cables embedded in roadways charging vehicles on the fly via induction! Problem solved.

DTsea | November 22, 2014

Starventure, when we are able to keep up with potholes then we can start talking aboy ripping up 40000 miles of interstates for the convenience of 100000 evs.

Or not.

DTsea | November 22, 2014

About not aboy. Phone. Sigh.

Brian H | June 4, 2015

↑Incoherent nonsense. There is no separate engine, just a battery-driven motor.

DTsea | June 5, 2015

Batterybhai you need to be over in the chevy volt forum | June 9, 2015

If you start out driving downhill, you will be able to charge the car while driving. After you reach the bottom of the hill, you may have enough charge to continue driving to a Supercharger. There you can charge for free and then return to the top of the hill. This would be the Tesla corollary to perpetual motion.

cbmdmacair | October 31, 2015

I cannot believe there are no electrical engineers who have bought at tesla and not
figured out how to hack into the charging system in order to enable on the fly charging
from a generator. It clearly would require gasoline, but the new X that I am waiting for
allows towing. I just need a brave and smart electrical engineer to devise and aftermarket
method of charging on the fly. They did the Prius plug in hybrid that way before Toyota came
out with a lessor one. I live in San Diego and there were two engineers that bought the first prius
and the Cruise control hardware was in but Toyota did not put the stalk in until many years later.

cbmdmacair | October 31, 2015

If there are any engineers willing to consider this maybe we can get Tesla to do it
themselves. BMW has the i3 but Califronia Air Resources Board will only allow it to
come on after 75 % of battery is depleted. How crazy is that if you would like to do
a long trip and run it the whole time??

Chris Bickford MD
858 531 0505

We need Elon for Mods.!!!!

Grinnin'.VA | October 31, 2015

@ cbmdmacair | October 31, 2015

>> I cannot believe there are no electrical engineers who have bought at tesla and not figured out how to ... enable on the fly charging from a generator. <<

^^ Have you considered the possibility that there is no known practical way to make good use of such a scheme?

BTW, Tesla could have included a small ICE in the MS, making it a plug-in hybrid. They decided that this wasn't worth doing. And they seem to have some world-class engineers. Yet, you think you understand this issue better than they do. IMO, your sense of self-confidence is a bit over the top.

Red Sage ca us | October 31, 2015

cbmdmacair: What planet are you from? Here on Earth, the Toyota Prius has an itsy-bitsy, teensy-weensy, teeny-tiny, lil 'ol 1.4 kWh battery pack. Even the lethargic 1.8 liter engine of a Prius is enough to keep that topped up while burning gasoline. Criminy.

vperl | October 31, 2015

Soon, the laws of stupidity will be enforced.

Run for the boarder.

Ross1 | November 1, 2015

Prius: one mile range, is that true?

Ross1 | November 1, 2015

@ vperl: What is a boarder ?

Over here it is someone who lives semi permanently in your home and pays 'board'.

Or is it the person who stands on the running board of a kia?

Or a train passenger?

" Soon, the laws of stupidity will be enforced."


vperl | November 1, 2015

Ross, ever heard of spell checker, I made mistake.

You just proved to be a bad guest, in my country, please leave.

Got complaints, go home.

Rocky_H | November 2, 2015

@cbmdmacair This sounds like: "Someone should take a car and then modify it by cutting off the back half of the body and attaching an open bed with a tailgate, so you can haul big things, or dirty or wet things that you wouldn't want in the interior of your car."

Uh, yeah, what you're describing is called a truck. You should get a truck.

Dude, if you want a plug-in hybrid with a gas engine, you should get a plug-in hybrid. There are plenty of them to choose from. A Tesla is purposefully not that, so it's no wonder no one is interested in changing it into that.

Remnant | November 5, 2015

@ Anonymous1598 (OP, November 4, 2014)

<< ... rotational energy from the front wheels [is] essentially being wasted. Would it be possible to, instead of putting a motor in the front, put a generator in the front or run the front motor in reverse all the time ... ? >>

Whatever portion of the energy that moves the car you recapture to charge the battery will reduce the car's motion, resulting in BRAKING.

This is what "regenerative" braking does already, but only to the extent you need to reduce the speed of the car.

If you overdo it, you waste the very kinetic energy you had imparted to the wheels in order to move the car, whether you "ride the brake" or otherwise use the energy for an alternate purpose.

In other words, you need to make up your mind: move or brake? It's a waste to do both at the same time.