# Ultra Capacitors over Batteries for Motorcycle?



## pathrunner (Aug 30, 2016)

So, I have a 1981 Yamaha Maxim that hasn't worked for years. I was originally going to make one of my two cars electric, but after some discussion with my wife, we decided to start with the motorcycle. 

I was reading up and came across someone who had used ultra capacitors for his scooter and I saw many advantages for it as well as some disadvantages.

First, I know I need a resistor setup because capacitors, like excited teenagers, blow their loads all at once. I have looked up a few plans for them and have an idea which I want to use.

The next disadvantage is of course that capacitors don't hold as much as batteries. However, I work literally 3 miles from my house and would only be using my bike to commute to work and back. 

The advantages for me seem pretty substantial. First, the charge time would be extremely quick. I could literally be ready for a quick drive in the time it takes to fill a tank with gas. Second, there is a multi charging station at work that people use for electric cars, bicycles, and scooters. So I would only need a small bank as well.

Best of all, because the bank would literally be the size of an actual brick, I could literally put the brick in my backpack and using a keyed connecter, would basically eliminate a theft risk.
Thoughts?


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## Duncan (Dec 8, 2008)

I think you need to redo your calculations!

(1) - recharge time is limited by the power of the charger Nothing to do with the batteries

(2) UltraCaps are only OK for about 2v - so you need to put lots in series
BUT capacitors in series are like resisters in parallel - the capacitance goes down

So say 100v and 2 Farad capacitors - if you put 50 - 2 Farad capacitors in series then your capacitance is 2/50 = 0.04 Farads
To get back to the 2 Farads you would need 50 strings of 50 capacitors

Then you have the problem that you need to go down to zero volts to get the energy out of a capacitor 
With a battery the energy is from ~ 3.6v to 3.1v (depending on the chemistry)


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## Karter2 (Nov 17, 2011)

Yes, you need to research ultracaps a lot more !..
But in the meantime, for that 3 mile commute, sell the Maxim, and buy an Ebike or convert an existing pedal bike to electric. It will be much cheaper and healthier.
A "brick" sized pack of lithium cells will get you there and back several times between charges.....and probably quicker than riding the Maxim if you have any traffic to deal with.


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## Evilsizer (Jan 25, 2010)

at 3 miles, wouldnt it just be better to get a E-bike or ebike-kit?
i mean even with lead batteries
http://www.ebikekit.com/electric-bi...or-w-sla-sealed-lead-acid-battery-10-16-mile/
they are sub 1k and get you up to 20mph with 10-16miles range.
or get the lith setup little over 1k and same speed higher range.
http://www.ebikekit.com/electric-bi...w-36v-li-ion-lithium-ion-battery-12-26-miles/

also have kits for 28mph as well, didnt look at range. one of the first links i found through google, i was tring to find some other kits that are worth the money. i cant seem to remember the name so i settled for that site.


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## Duncan (Dec 8, 2008)

At 3 miles why bother with the "E" a simple push bike would be ideal - or one of those little scooters - or even walk


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## Karter2 (Nov 17, 2011)

Building/converting an Ebike would give you some valuble experience and learning of the basics of EV systems, motors, controllers, batteries, chargers, etc , with minimal financial risk , yet would also result in a very useful transport tool at the end.


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## pathrunner (Aug 30, 2016)

The distance isn't the reason to do it at all. It's the experience of the whole thing. I've been looking at it and I am pretty sure I can fit enough ultras into the gas tank of this thing to get even more distance out of it and mod it for the charger.


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## Evilsizer (Jan 25, 2010)

pathrunner said:


> The distance isn't the reason to do it at all. It's the experience of the whole thing. I've been looking at it and I am pretty sure I can fit enough ultras into the gas tank of this thing to get even more distance out of it and mod it for the charger.


you are going to need alot of super-caps to get any kind of range. there is a reason that even with super-caps they are not used for powering hybrids or ebikes. let me see if i can find the video from a while back... i could not find the eletric go kart video a watched a few years ago. they connected a super-cap bank or boosts cap's from maxell in a system. that as they braked it would charge, they would then hit a button that would then in parallel with the battery system dump all that stored energy into the motor for "turbo boost". with as many caps as they had on the kart, they only had about 2-3secs of "boost" to accelerate.

a video that might help, since there is a comment in there worth reading from darkshadowX5 to another commenter.
https://www.youtube.com/watch?v=brw6sC8D2_w

in the end, do to you want to do with super caps your going to need more money then going with lipo or even smaller agm batteries. then the size for a super cap bank, its going to be larger then even lead battery.


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## Kevin Sharpe (Jul 4, 2011)

Here's one application for ultra caps...

http://fast-charge.org


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## dcb (Dec 5, 2009)

Kevin Sharpe said:


> Here's one application for ultra caps...


Meh, remains to be seen, but it still doesn't seem to add up on paper as an advantage. I mean this is a huge pile of caps, and they're gonna take a hit with the voltage dropping so quickly (you need high voltage the most at the end of the race, but these will drop linearly), which is what people have been saying here...










granted it will charge quickly, but that isn't how they measure a drag race.


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## WolfTronix (Feb 8, 2016)

E = 1/2 C*V^2

Note, that the above equation assumes that you discharge the capacitor from your highest voltage to 0V...

If your controller cuts out at say 120V, and you charge your caps to 180V, the 'V' term is actually only 60V, (180V-120V).

With out a bi-directional buck-boost converter, you can't utilize the full stored energy of the capacitor.

The same problems happens when you put supper caps in parallel with a battery pack, (you do get a slight performance increase, but that is due to lowering the ESR of the pack)... 

The voltage of the caps ends up tracking the voltage of the battery pack, so you never utilize all the stored energy of the super caps.

you really do need active electronics between the super caps and the motor controller / battery pack.

Also, those large Maxwell Boost cap modules can be found used in "hybrid" passenger buses (along with a bi-directional buck-boost converter).


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## pathrunner (Aug 30, 2016)

I have a buck booster right now. It's part of the controller board with the resisters. The rest, something I have to keep in mind for sure. Luckily I married an electrician and she builds boards. 

I'm not sure if this is going to end up being worth the effort, but it is going to be fun to try to take on. I'm also looking at using my 3D printer for some frame and decorative parts.


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## Kevin Sharpe (Jul 4, 2011)

dcb said:


> Meh, remains to be seen


Phil Edwards previous bike holds the UK electric standing start quarter-mile record (set in 2011 with a best time of 14.124 seconds) and his new bike has attracted a lot of sponsorship... I'm going to wait and see whether his ultra caps can deliver 6 seconds and 200 MPH before dismissing the technology


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## dcb (Dec 5, 2009)

Kevin Sharpe said:


> Phil Edwards previous bike holds the UK electric standing start quarter-mile record (set in 2011 with a best time of 14.124 seconds)


that is laughable, a brammo can beat it.




Kevin Sharpe said:


> and his new bike has attracted a lot of sponsorship...


As an engineering type, the site really smells, it says it wants to inspire engineers, but it really just wants money. It is downright insulting to be so presumptuous to think that a BS concept like ultracap dragbikes would be anything other than a scam, leave engineering out of it. You might as well sell overunity.




Kevin Sharpe said:


> I'm going to wait and see whether his ultra caps can deliver 6 seconds and 200 MPH before dismissing the technology


There is nothing to dismiss since nothing was ever proven, only a crapton of hype and misinformation. You might be waiting a loooong time.


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## pathrunner (Aug 30, 2016)

Well, given that capacitors love to drop their load as fast as possible, I don't think it is outside of the realms of possibility to use them for short runs of extreme speed.


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## Kevin Sharpe (Jul 4, 2011)

dcb said:


> that is laughable, a brammo can beat it.


Not in 2011... Phil's record is real world and documented, not some armchair pipe dream.



dcb said:


> As an engineering type, the site really smells, it says it wants to inspire engineers, but it really just wants money. It is downright insulting to be so presumptuous to think that a BS concept like ultracap dragbikes would be anything other than a scam, leave engineering out of it. You might as well sell overunity.


Not much of an "engineering type" if you're closed to other possibilities... Personally I'm happy for people to try anything they believe in and I support Phil's attempt to do just that! 



dcb said:


> There is nothing to dismiss since nothing was ever proven, only a crapton of hype and misinformation. You might be waiting a loooong time.


Let's wait and see shall we?


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## dcb (Dec 5, 2009)

Kevin Sharpe said:


> Let's wait and see shall we?


LOL, you first have to get the energy density down to about a megawatt for 7 seconds at 250 lbs, or you shouldn't use the word "engineer".

edit: I think this is why I'm associating this with overunity, those folks don't know the difference between voltage and power, and the ultracapacitor crowd don't know the difference between power and energy it seems.


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## kennybobby (Aug 10, 2012)

Back of the envelope calculations:

It would take 1000 HP (746kW) to send 2500 lbs down a 1/4 mile track in 6 seconds reaching 200 mph.

Equate the kinetic energy at 200 mph with the energy in the capacitor supply assuming a 50 V drop (sag).

So it would require only ~3600 F of capacitance assuming a 50 V drop. This would be ~1.25 kWh of energy per run.

By comparison, a Tesla P90D pack voltage sags about 80 V during a 0-60mph acceleration run in ~3.2 seconds.

The voltage drops from 400 to about 320 while pulling 1300 to 1500 Amps peak during these sort of runs.


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## dcb (Dec 5, 2009)

fwiw, I was basing 250lbs and 1MW on the lawless pack, 
http://www.diyelectriccar.com/forums/showthread.php?p=301151 14.5kwh. 


but with 2.7v capacitors, getting to 400v at 3600F would take roughly 148 capacitors at 533000F in series... (or 22,000 3600F capacitors....)


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## kennybobby (Aug 10, 2012)

Ioxus makes a 2.7V 3000F capacitor cell such as shown in the picture above.

http://www.ioxus.com/english/products/cells/

It has a peak current of 2700 Amps for 1 second, weighs 510 gms, or a little over 1 lb each. And we need 22,000 of them.

So unless there is some magical electrickery that we don't know about, then a 400V, 3000F pack would weigh about 11 tons! There must be something that we're missing...


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## Karter2 (Nov 17, 2011)

The maths has been revisited many times here and on other projects/sites with the same conclusion....ultracaps just are not practical for normal traction pack use.
...so how does a project like that drag bike, with some apparently experienced technical support groups, get so far into a design without questioning the physics of what they need.


> ..... with 2.7v capacitors, getting to 400v at 3600F would take roughly 148 capacitors at 533000F in series... (or 22,000 3600F capacitors....)


...yet they say they are using only 640 of those caps ??
Either the maths is wrong, or they are fooling themselves ?
Has anyone on Twitter questioned them about this ? ( i dont use Twtr !)
..or is this another case of " The Emperors new clothes".


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## Evilsizer (Jan 25, 2010)

well something doesnt seem right with that quote you just posted.


> .. with 2.7v capacitors, getting to 400v at 3600F would take roughly 148 capacitors at 533000F in series... (or 22,000 3600F capacitors....)


to reach the voltage you need 148 caps in series, then due to series wiring you lose Farads. you go from 3600F/148caps=24.324F per string of 148caps in series for 400v+/- a few volts. then if these are connected to a controller then you have a smaller range of of voltage. 

would it then be a side effect of the way the voltage on caps drop that even if the cap bank was directly connected to the motor via a relay. that it would then slow down towards the end of the track? since voltage = rpm, it would effectively be like braking with out touching the brake pedal.

i dunno just me but if EV racing in cars, use boost caps for a quicker way to accelerate. even in bikes if you could find a way to do a small pack to 1-2secs boost, could make all the difference. 

what does the future hold for super-caps, who knows? i mean with them still working on carbon-nano tubes. reading some of the papers about how good they are at electrical conductivity. could we then increase energy storage of caps by using carbon-nano tubes layered on the copper windings in the cap. more over we could use the same approach with carbon-nano tubes on batteries. as much as it would be nice to think we could just add a few layers of carbon nano tubes to current batteries and caps. im sure chemistry in both caps and batteries would need to be tweaked. this is well beyond what i can do but wonder if someone or group is working on this right now. as i havent read anything about any testing on what im thinking about.


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## dcb (Dec 5, 2009)

Evilsizer said:


> well something doesnt seem right with that quote you just posted.


I didn't come up with the 3600F figure, but otherwise we are saying the same thing, 148*148 = 22,000, 3600/148=24.32.

The other thing is that acceleration is absolutely not an issue AT ALL, the number one problem is range (even possibly for 1/4 mile), and ultracaps just murder it completely.


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## pathrunner (Aug 30, 2016)

Kevin Sharpe said:


> Here's one application for ultra caps...
> 
> http://fast-charge.org


Well, my Buick literally exploded, so I turned around and bought a Nissan Leaf. I'm still gonna look at converting my wife's VW New Beetle.


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## Kevin Sharpe (Jul 4, 2011)

"Rather than working with conventional lithium-ion batteries, Fisker is turning to graphene supercapacitors."

http://uk.businessinsider.com/henri...tionary-battery-tech-for-electric-car-2016-10


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## dcb (Dec 5, 2009)

yah, they will be pulling a delorean soon, running cocaine or something to try to make their numbers. They didn't solve sh!t, couldn't even manage A123 batteries right, yet 400 mile range on their special ultracaps, LOL!


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## dcb (Dec 5, 2009)

fyi, did look into it more, they say it is comparable to lead on energy density (factor of 2?) but the lithium comparisons are based on a 0.0005ah cell which is mostly packaging I'm sure. Plus I don't see a weight comparison. Not really enough info to support their 400 mile claims. And the fact that they present lithium ion as drastically worse than lead should be a big red flag.

http://www.pnas.org/content/112/14/4233.full.pdf

note logarithmic scale (things are farther apart than they appear)


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## Sunking (Aug 10, 2009)

This reminds me of the movie Dumb and Dumber.


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## Kevin Sharpe (Jul 4, 2011)

"Augmented Optics reveals new material that can charge a car as quickly as filling up with fuel, and it could make batteries redundant"

http://www.diyelectriccar.com/forums/showthread.php?t=179706


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## dcb (Dec 5, 2009)

what information did you see in that article that you found investment worthy (in either time or money) specifically as it relates to electric vehicles? Especially the DIY variety?


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## Kevin Sharpe (Jul 4, 2011)

dcb said:


> what information did you see in that article that you found investment worthy (in either time or money) specifically as it relates to electric vehicles?


Elon Musk - “If I were to make a prediction, I’d think there’s a good chance that it is not batteries, but super-capacitors.” 



dcb said:


> Especially the DIY variety?


Many people are using components from OEM cars in their DIY conversions (Tesla and Nissan drivetrains and batteries for example) and I see no reason why we can't use OEM super capacitors in the future.


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## dcb (Dec 5, 2009)

Kevin Sharpe said:


> Elon Musk - “If I were to make a prediction, I’d think there’s a good chance that it is not batteries, but super-capacitors.”


he hasn't repeated that since 2011, and is actually betting on batteries these days, if you haven't noticed.

edit, and that is incredibly sad reasoning...


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## Hollie Maea (Dec 9, 2009)

If you really need to charge in 2 minutes (you don't), then make your battery ten times bigger than you need and just charge up the 10% SOC you need in 2 minutes. It will weigh the same and cost the same as a Cap bank that matches the 10% you need. And it will deliver its power at relatively consistent voltage.

If you can somehow manage a 4 minute charge time, then just make your battery 5 times bigger and use 20% of its SOC. You'll be half the weight and cost of Caps!

Capacitors as a traction energy storage system make the most sense for people who think that discharge time (and its converse, C rate) is an actual direct measurement of performance. In the real world, running out of charge in 10 seconds isn't actually a "feature".


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## Duncan (Dec 8, 2008)

Hi guys
I agree entirely about the present generation of Supercaps - too heavy too expensive
and the charge rate is a red herring

But the newspaper article talked about a 1000 fold improvement!

Batteries are going to get better - but maybe twice as good is going to be the limit

What are the physical limits for supercaps? could we be talking about something 1000 times better?


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