# 1000 HP dragbike with Ultracapacitors



## kennybobby (Aug 10, 2012)

Calculatus eliminatus:
[edited]
[The acceleration for a 6 second 1/4 mile is 73.33 ft/sec^2, or about 2.27 g., from x=.5A t^2]

Take [their advertised] 1000 Hp over 6 seconds to determine the energy (or work over 1/4 mile) to determine that the [force on the accelerated mass] is 2500 lbs.

[1000 hp x 550 x 6s = 3,300,000 lb-ft, or 1,243 Whr.]

[Divide the 2500 lb force by the acceleration to get the mass = 34.1 and the bike weight is ~1100 lbs.]

Equate the kinetic energy, [1243 Whr] to the capacitor energy, 1/2 CV^2, using 3p = 6000F and 6000/210s = 28.6 F for C, it looks like they are assuming a voltage drop of only 9.4 V in the pack during the 6 second burn.


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## dcb (Dec 5, 2009)

also they have stated they want a sub 7 second bike (1/4 mile), comparable to the rocket. The rocket has a 14.kwh pack that makes about 1 megawatt for 7 seconds or thereabouts, and weighs 250 pounds. Basic physics would mandate that replacing the batteries with capacitors (and any necessary converters) and expecting the same performance would require that the energy output at that power level divided by the weight of the energy source (batteries vs caps and converters), needs to be equal.

I recon the caps alone weigh 541 pounds, and 1000hp is %25 less than 1MW. So already the energy source is over twice as heavy and less powerful than the current NEDRA leaders packs, and 28F really sounds like it is gonna come up short, but I haven't dug into the farads required much (seemed pointless given all the other red flags).

F=M*A

edit, I'll see if I can do an ltspice simulation of 28F @600v putting out 1000hp (even though it needs to put out more than 2MW for 7 seconds to be competitive on a density basis)


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## kennybobby (Aug 10, 2012)

just trying to run back-of-the-envelope numbers to see where/if any assumptions run off the tracks...

so they need a motor that turns 22,000 RPM and makes 1000 HP, so 238 ft-lbs of torque at 22k using 1255 Amps from a 600V pack.

1255 Amps/3p is about 420 Amps per cell over 6 seconds is 2520 A-s or 2520 Coulombs. Each 2000F cell holds 5400 Coulombs at 2.7V, so theoretically there is enough charge. Another way to look is the entire pack, 28F x 600V, holds 17,160 Coul and a 6-second burn of 1255 Amps is about 7,600 Coul.

Now here is where the problem surfaces, when the cells give up their charge the voltage drops. From a best case 2.85V x 2100F = 5985 C full less the 2520C burn leaves 3465 C. Now what is the capacitance of the cells? If 2000F, then the voltage will be 1.73 per cell, or a sag/drop of 1.11 V per cell. Over 210 cells, the pack will sag 234 Volts, which is a big difference to the 9.4 V sag used above to determine the capacitance required for the pack. This is a big deal breaker, plus can an inverter be made to tolerate this much sag and still drive the motor with the required power to make the run?

i think this should be tested with just one cell to prove whether or not it sags under 420 Amps for 6 seconds (and how hot it gets).


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## dcb (Dec 5, 2009)

ok, got it sorted, 28F @ 600v is *just* enough to make 1000hp for about 7 seconds on paper, but it looks like they are making some terribly naive assumptions about being able to convert a 3 volt source at 300,000 amps at the end of the race (plus extra weight and conversions and that they are 254,000 watts short of the rocket).

edit: so it starts at 600v @ 1250a, and at 6 seconds it is at 3750 amps at 200v, and then it falls off a cliff, surely before the race is over.


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## dcb (Dec 5, 2009)

there is also an increased risk of reversing a cap with no margins and over a 3+x voltage drop over a string of 210 caps @ thousands of amps.

edit: apparently that isn't catastrophic, possibly some capacitance loss. http://www.cooperindustries.com/con...pacitors/BUS_Elx_App_Notes_App_Guidelines.pdf


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## Karter2 (Nov 17, 2011)

Just a couple of points..
Did they clearly statr the pack configuration of 3p, 210s ? Or is that a guess ?
On their facebook page they stated 640 caps in the pack ?..just a estimate ?
How sure are you they are not using the 3000F caps ?

Im not being critical here, just trying to understand why yesterday you were suggesting it would need 22,000 of the 3000F caps to do this, but now it looks like they are a lot closer with <1000 caps ??


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## dcb (Dec 5, 2009)

yah kenny threw out the 3600F figure in the other thread, but the simulation (rough approximation) and his research (digging through blogs instead of a scientific or engineering style organization of testing and data by the folks making the claims) have indicated that it is off, but 28F at 600V is still quite a bit short, if you were to take the existing NEDRA leader and replace the battery with 28F ultracaps and a boost converter made of unobtanium.

edit: I don't think it matters if they are 3000F, assuming they are proportionally heavier. ultras have better power density, but it takes energy to do a 7 second 1/4 mile.


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## Karter2 (Nov 17, 2011)

Even avoiding the calculations, i dont understand how they dont see the simple fact of the pack weight is a big hint that something is wrong with the basic concept.


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## dcb (Dec 5, 2009)

more swags on the rocket bike:
http://www.nitrousexpress.com/oldwebdocs/hpcalculators.htm

if you put in 2000 lbs, and 1340 flywheel hp(battery hp?), you get a 7 second 1/4 mile. So the rocket bike is probably less than 2000 pounds w/rider, that 13 inch GE motor though... So the target is somewhere around the 1MW:2000lbs ratio (sustained for 7 seconds), which doesn't *quite* jibe with the Calculatus in post 2 (746kw @ 2600 lbs = 6 second 1/4 mile). There's a lot of drag at 200mph though, so I dunno how the calculator works.

edit: here is all that page does, I don't see drag factored in, ah well, expect more nasty guesses 


```
document.input.et.value=Math.pow((document.input.weight.value
    /(document.input.hp.value*.854)), (1/3))*5.825;
```


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## kennybobby (Aug 10, 2012)

Karter2 said:


> Just a couple of points..
> Did they clearly statr the pack configuration of 3p, 210s ? Or is that a guess ?
> On their facebook page they stated 640 caps in the pack ?..just a estimate ?
> How sure are you they are not using the 3000F caps ?
> ...


# of cap cells was from reading the blogs, and then:
i just counted the 3p modules as shown in their diagram above, and
i counted the number of boxes in their mock-up picture, 8 top row, 16 middle and 18 bottom. Each box holds 15 cells. Both methods gave 630.

i didn't look at the facebook, so unaware of 640.

Cap size 2000 vs 3000:
This was determined both by weight and length.
A ruler was shown in the mockup photo on the boxes, ~3 boxes per 12" ruler, so about 4" length per cell (the 2000F cell is 108.1mm),
The caption under the shipping pallet indicated 250 kg, the 2000F cell weighs .39 kg, the 3000F cell weighs .51 kg. 640 cells x .39 = 249 kg. Maybe they got 10 extra to use for prototype and spares.

i think yesterday we were using standard EE math for series and parallel strings of capacitors to get to the 3600F, which was calculated by equating the kinetic energy of a 2500lb bike at 200 mph with the Capacitor energy with a 50V sag--this was before parsing thru all the blog pages trying to find tech details. 

After finding the hive drawing and photo with the 3p connecting plates, etc. it was possible to determine the actual capacitance and voltage of a 3p210s pack made using the 2000F cells. This configuration yields a total capacitance of 28F at 600V, and could only work if the pack voltage only sagged ~9 Volts. Feel free to double check and challenge my numbers, i don't want to make a mistake in the basic data that affects the calculations and predictions.


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## Karter2 (Nov 17, 2011)

No, thats ok Kenny, thanks for the clarification.
I am not too familiar with ultracap powerbanks so i just wondered why the big discrepancy between what we thought would be required conpared to what they are doing.
It still seems as if they are way off in their design thoery, which is even more surprising when you look at who they are working with.


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## kennybobby (Aug 10, 2012)

i'm puzzled by it also, hence the investigation--do they know something that we don't know?

It's almost as if they are using the caps as battery cells with no consideration for the reduction due to stacking in series...


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## dcb (Dec 5, 2009)

more comparative data points for drag bikes (roughly speaking):
http://www.knfilters.com/news/news.aspx?id=2461

1030 lbs (rider?)
1000 hp
2 speed
< 5.8 second 1/4 mile @ 245mph
37 pounds of nitromethane per run (mix?)
which is maybe 3.5kwh equivalent, but we know they ICEs aren't real efficient, giant wall of flame from disassociated hydrogen from water in exhaust. (5.765 seconds at 227.10 MPH here https://www.youtube.com/watch?v=npNkwVw-V5I)

note, I learned there is some funny business too, some (all?) top fuel races are only 1000 feet instead of 1320 feet, so WTF.
https://en.wikipedia.org/wiki/Top_Fuel

<sigh> perhaps not top fuel dragbikes though. http://www.cycledrag.com/top-fuel-motorcycle-1000-drag-racing-when-is-now


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## Frank (Dec 6, 2008)

I'm on a tablet so research is hard, but a number of years ago a group of students raced an EV1 (I think) in a 1/4 mile drag race. They pushed it to the line to converge energy.

Also, without following numbers here, don't caps decrease dramatically in voltage as they yield energy? Result would be massive sag, no?


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## Frank (Dec 6, 2008)

http://universe.byu.edu/2004/05/11/students-race-ultracapacitor-for-first-time/

http://electrifyingtimes.com/maxwell_EV1.html

I'm sure there's more out there on the byu project.


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## dcb (Dec 5, 2009)

Frank said:


> Also, without following numbers here, don't caps decrease dramatically in voltage as they yield energy?


Yup, I put a constant power graph in post 5., granted races aren't really constant power, but they aren't constant efficiency either, so it is a first order approximation.




Frank said:


> I'm sure there's more out there on the byu project.


they changed everything though, i.e. cut the weight in half by removing who know what and the EV1 has no lithium performance figures to compare to. I've been looking at other drag bikes because they should be similar in weight and aerodynamic drag and have some performance numbers to compare to.


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## zaxxon (Jul 11, 2009)

This simulation shows if one had a controller that could operate with an input range from 600 to 300 volts and supplied 2000 amps at 300 volts to the motor, then one would expect to get around 800 HP for 4 seconds using a 28F capacitor charged to 600 volts. (Note: This is for a linear controller. Result should be better with a switching controller)


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## zaxxon (Jul 11, 2009)

With a switching type buck converter, this simulation shows one could expect to get around 800 HP for 6.3 seconds using a 28F capacitor charged to 600 volts.


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## dcb (Dec 5, 2009)

ltspice is fun, but you might be over complicating it a bit  the controller design isn't relevant per-se, indeed changing everything around will invalidate the comparison between caps and batts (excepting for possible power conditioning of the cap output to suit motor/controller requirements).

600V 28F 800HP(596800W) discharge (ideal components)= 300V @ 6.3 seconds, check.


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## zaxxon (Jul 11, 2009)

Agree, and each shows what is possible.


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## Karter2 (Nov 17, 2011)

Another tech article on the BYU ultracap EV1..
http://www.altenergymag.com/content.php?issue_number=04.04.01&article=dragster


> ?...
> With the decision made to use ultra capacitors in the race car, design and construction of the storage pack was begun. A preliminary estimate of the energy needs for the race, combined with the maximum voltage rating of the motor and controller, indicated that the car would need a storage pack consisting of 160 capacitors where each capacitor was rated at 2700 farads and 2.5 volts.
> 
> The capacitors were connected in series using copper bars for conductors. They were mounted in six sets of twenty-five plus two sets of five. This allowed the use of the original, "T"-shaped battery storage box which came with the EV1.
> ...


Race weight was 1801 lbs...1/4 mile was 15.94 Using a 400v, 400amp modified EMS controller.
So , max 160kW at the start line , and nothing left at the finish line !


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## dcb (Dec 5, 2009)

re: ev1
it sounds like about stock 1/4 mile performance after drastic weight reduction and cutting the range from ~100 miles to 1/4 mile...

https://avt.inl.gov/sites/default/files/pdf/fsev/genmot.pdf
MAXIMUM SPEED @ 50% SOC
At 1/4 Mile: 78.9 mph
At 1 Mile: 80.4 mph

a couple more data points (and variants)
https://en.wikipedia.org/wiki/General_Motors_EV1

They say it is "electronically limited" to 80mph, but I wonder if it is really BEMF limited, which would give you a KV approximation, i.e. the supercap version was still above ~300v at the end of 1/4 mile.

And 2.5v * 160 = 400v, and 2700F * 160 in series = 17F. So fiddling a bit with the simulation I get an average of 37KW (50HP) discharge, ignoring losses. Given that the byu car only gained 8mph in the last 1/8 mile, it was probably current limited by BEMF.

Note, I don't necessarily agree with the BYU conclusion (especially since it is from the lead age, it would have been closer to 100mph with an even lighter 400v lithium pack), though I imagine the PI probably felt like they had to say something encouraging for their capacitor sponsor or something. Also it looks like they just took an inverter and IGBTs (https://www.mrodrives.com/pdfs/e8001-03v.pdf) for a controller.

edit, looking at that manual, 300VDC bus volts is the lowest undervoltage detection setting for the 460v unit, and they mentioned getting undervoltage warnings at the end of the race, so that is probably how it went down.


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## major (Apr 4, 2008)

*BYU EV1 Drag racer*

I did the controller modifications on the EV1 power module for BYU. All the power electronics stayed OEM. It just involved the installation of an Yaskawa G5 control card and other bits. GM removed all the control electronics to disable the car prior to the donation. The resulting DC bus range was 400 to 170V. OEM adverstised power was 100 kW. After the mods I think we exceeded that but don't recall the number.

major


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## dcb (Dec 5, 2009)

Hi Major, hokey smokes, you've been at this a while! I recall you mentioning using a regular inverter in a car, but didn't put it together.

So what do you think in 2016? a lot of folks are speculating about future capacitor improvements, meanwhile the NEDRA folks cut hundreds of pounds off a lithium pack and get under 7 seconds.

despite the improved cycle life, do you see supercaps competing in drag racing (without some handicapping system)?

edit: here's a breadcrumb trail of Major's ultracap experience https://www.google.com/webhp?source...TF-8#q=major ultracap site:diyelectriccar.com


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## dcb (Dec 5, 2009)

found an online version with pictures (sorry if it is pirated...) 


http://pdf.directindustry.com/pdf/m...capacitor-power-drag-racecar/16729-47991.html

you can see they hit the knee 3 seconds into the run (or it is a controller artifact) and its down to nearly 300v already, making ~116kw at the capacitor bank. And they are at 1/8 mile at ~ 10 seconds, where distance/time goes nearly linear (speed goes fairly constant) at about 50kw pack power. Finally down to about 22kw at 1/4 mile. ev1 takes maybe 17kw to hold 77 mph, less if you cut out 1000 lbs.









nice to see some actual data.


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## Karter2 (Nov 17, 2011)

So i guess we have to see how far off the mark the "Fast Charge" system is.
Sounds like they wont make the 6 sec target, but should we start a book to guess what time they get after say, the 3 rd full timed run ? 
..I will take 9 secs .


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## Frank (Dec 6, 2008)

I'm not sure what advantage the caps would really have over modern LiPo's, other than the cool factor that is.


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## Karter2 (Nov 17, 2011)

The Caps are no advantage,.
Infact a definite disadvantage, in power , size , and weight.
...That is the big mystery .


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## dcb (Dec 5, 2009)

Karter2 said:


> That is the big mystery .


Not really, I mean if it looks like a scam and smells like a scam...

There are so many things they have pushed out to the web that are misleading or flat out wrong, and nothing demonstrating ANY scientific rigor, and they hide behind the "kids in STEM" angle.


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## Mini-mayhem (Apr 27, 2015)

it should be a fast bike with those capacitors


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## Duncan (Dec 8, 2008)

Why do you say that? - they are heavier with much less energy than batteries


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## Mini-mayhem (Apr 27, 2015)

The capacitors can deliver the power, lipos struggle to provide 2000A


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## dcb (Dec 5, 2009)

Mini-mayhem said:


> The capacitors can deliver the power, lipos struggle to provide 2000A


big difference between power and energy, a race of length > 0 requires energy (power * time), and lipos don't appear to be struggling at making power while having much greater energy density. I'm not sure it matters how much >0, but it looks like in this instance the caps would be much heavier for less power and much less energy.

heavy bad.


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## Frank (Dec 6, 2008)

Mini-mayhem said:


> The capacitors can deliver the power, lipos struggle to provide 2000A


I can assure you that modern LiPo's have no problem at all delivering current!


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## Karter2 (Nov 17, 2011)

Mini-mayhem said:


> The capacitors can deliver the power, lipos struggle to provide 2000A


 For power you need amps, and volts 
Lipo can deliver the 2000amps 
Capacitors cannot maintain the voltage


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