DIY Electric Car Forums banner
1 - 17 of 17 Posts

·
Registered
Joined
·
24 Posts
Discussion Starter · #1 ·
Hi
I have been thinking a lot about that last remaining category of ICE which seemingly cannot be beaten by an EV: The Top Fuel dragster.
Here, we're talking 10000Hp+ (estimates, as it's apparently hard to put a 3-second car on a dyno), but just for 3 seconds, and a rebuild is needed at the end of that.
Conversion of energy from electrical to mechanical should be doable in a few hundred kg, since it's such a short time. And it's not like you're gonna be able to fine tune the current any better than just closing and opening a contactor in that timeframe anyway, allthough IGBTs exist which can do it.

But what sort of energy storage, now or within a reasonable time frame, could be able to deliver that amount of current?
About 2kWh is probably enough, but is it possible?

Storing that amount in capacitors isn't technically hard, there's a 600uF 900V cap available which can do 4200A peak. Slap 10 of those in there and you have the energy. But the discharge curve works against you, as the voltage drops quickly, leaving little voltage at the end of the race, when you need it the most to overcome the back EMF. Maybe, since these are light enough, you just overspec enough to coast over the finish line.

Would it be possible? How dumb, on a scale from Tesla to Top Fuel Dragster, would it be?
 

·
Registered
Joined
·
103 Posts
Interesting thing to think about but, IMHO, the biggest challenge is to transmit the energy from the energy storage to the E-motor and then to the wheels. This is easy in an ICE as the energy conversion is done after the fuel delivery inside the engine and done once (nitromethane is also a massively energy dense medium).

For a EV, the conversion is done from chemical to electrical inside the energy storage, and then you have to transmit the electrical energy to the E-motor where it is converted again to mechanical energy. Not only do the conversions take "time" and create losses, moving around that much energy in electrical form is a huge challenge.

And then initial thought is you would need to get the voltage up...way up...to keep the currents down to any level reasonable to transmit in a vehicle... But then you have huge isolation issues in the inverter and e-motor...
 

·
Registered
Joined
·
3,096 Posts
Again, the rail gun does it with enough power to launch a jet off an aircraft carrier.

Just a matter of rolling that linear motor up into a rotary and storing the energy in extremely high voltage cap banks. It only needs a 3 second whack.
 

·
Registered
Joined
·
7,970 Posts
But what sort of energy storage, now or within a reasonable time frame, could be able to deliver that amount of current?
...

Storing that amount in capacitors isn't technically hard, there's a 600uF 900V cap available which can do 4200A peak. Slap 10 of those in there and you have the energy. But the discharge curve works against you, as the voltage drops quickly, leaving little voltage at the end of the race, when you need it the most to overcome the back EMF. Maybe, since these are light enough, you just overspec enough to coast over the finish line.
This seems like a great application for capacitors, and the voltage drop could be compensated by starting the run with much higher voltage in the capacitors than the motor needs, but the aircraft-launching catapult on the USS Gerald R. Ford uses flywheels.
Wikipedia: Electromagnetic Aircraft Launch System - Energy storage subsystem
It is storing much more energy than the dragster would need, simply because the vehicle being launched is so much more massive.
 

·
Registered
'69 VW Bug
Joined
·
7 Posts
About 2kWh is probably enough, but is it possible?
Scroll down in this link and check out the specs on this race car. 1.6 million watts, 2000 amps & 800 volts (!!)

 

·
Registered
Joined
·
103 Posts
Scroll down in this link and check out the specs on this race car. 16 million watts, 2000 amps & 800 volts (!!)

I think you missed a decimal... 1.6 million watts... And while cool, 2000 amps and 800 volts and 1.6MW isn't really that extreme...but it is cool all packed into a dragster. Just in comparison though...the 10,000Hp number above for a typical top fuel dragster/funny car is about 7.5MW

Just FYI...the company I work for is currently building a 5MW 2000V 4000A battery test system for a earth moving equipment company... It's huge...
 

·
Registered
Joined
·
24 Posts
Discussion Starter · #9 ·
Yeah, it's almost an order of magnitude off, so with the better starting torque of electric motor maybe about half of the necessary power to compete with top fuel. About a third of what's necessary to win? But its pure guesswork from me, and we know it's nowhere close to that level right now.
 

·
Registered
Joined
·
1,765 Posts
Getting enough traction to sink the electric motor torque will be a huge deal. Even 1,000 hp gassers take time to develop that power, albeit in milliseconds, electric is full torque as fast as the semiconductors switch to on.
 

·
Registered
Joined
·
1,765 Posts
With electric, you can make the torque/speed curve anything you want. Which, in a way, is cheating.
Not cheating, gassers do have a variable function aka gas pedal, but pretty much everyone uses it as an on off switch. It IS kinda hard to precisely feather at launch. The only cheating aspect would be electronic control with a feedback loop, but that could be done on a gasser also, although much slower.
 

·
Administrator
Joined
·
6,443 Posts
We can buy off the shelf batteries with a C Factor of over 120 - That means that they deliver all of their stored energy in 30 seconds

A quick google finds batteries with a Pulse discharge of over 150

We want 10,000 Hp (guess) - 7.5 Megawatts - divide that by the 150C and we get 50 kWh - about the same size and weight as a Tesla battery

So the power supply should not be a problem
Cables and the like are not a huge problem as we are only thinking of a few seconds
 
1 - 17 of 17 Posts
Top