# super capacitors

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Joined: 02/22/2009
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Hi everybody

It cost 5400\$( http://ca.mouser.com/Passive-Components/Capacitors/Supercapacitors/_/N-5x76s/?Ns=Pricing|1 )
And here are caracteristics:

Do you think it would be interesting for electric motorcycle conversion or not ? if yes, why nobody has tries to do so ?
Because cost of course but probably not The real reason, no ?

Thanks for giving me your opinion

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Joined: 10/23/2008
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Re: super capacitors

Ultracapacitors are great, I used 10 x (2.7v 3000Farad Maxwels) on my solar bike, with thin flexi powerfilm panels charging the caps up.

I get about 10mins maximum ride time from my Utracap string that cost >\$400- Does that answer your question?
(And Takes a day of sun to recharge!)

And sadly capacitors drain with the voltage reducing down to zero, unlike batteries that keep a fairly constant voltage thro discharge.

Still its an area to keep an eye on for the future. If someone can come up with a 50v 10000Farad Capacitor then ...;o)

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Joined: 02/22/2009
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Re: super capacitors

OK

So, if I understand correctly, the problem with super capacitors is that they are ... capacitors ! ;-) they decrease voltage during discharge so speed will decrease too. That's this ?

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Joined: 10/23/2008
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Re: super capacitors

Yes the exponential decay of voltage is an issue.

There is a way round this, if you have a special controller.
Put simply say you have a 24v motor, then if you use a 60v capacitor string, the controller pulses its MOSFETS at a increasing frequency as the voltage from the string decays - giving a steady 24v

With the drop from 60v down to 24 you actually get about 90% of the energy out (because the energy stored is proportional to v squared)

Now there is no controller I know of thats built for this right now. The only way I can think of doing it is using a standard 60v pulsing controller with a variable throttle, but making sure the throttle isnt twisted very far when the string is at full voltage, but then having the throttle on full twist when the string becomes empty.

The great thing about Ultracaps is nearly infinite cycle life, and fast charging and discharging capability - so they do have some strong attributes!

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Joined: 02/22/2009
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Re: super capacitors

With LiFePo4 the problem is that we need BMS (and, with classic BMS we lost much power during charge)
One solution for ultracaps would be to choose high voltage ultracaps, for example 110V capable, to charge directly from power point and this would be converted on the bike into a lower value with anothers caps on output (calculated for 5 mn motor run ?). The advantage would be immediate charge and possibility to select between speed (voltage) and distance (amp).

My english is poor and perhaps it's not clear

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Joined: 10/23/2008
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Re: super capacitors

Ummm not really, the following reasons

1) Mains electricity is AC (not DC)
2) They dont make high voltage UltraCaps yet - They are all about 2.7volts (and ones that are 5.4v are made out of 2 x 2.7v etc)
3) You can buy high voltage capacitors but they only store small (microFarads) energy
4) I would never use high voltage capacitors in the >100v range, very dangerous
5) I dont think the problem with BMS systems is any lost energy from the charge source - the problem is they can be complex. Even strings of capacitors need to be balanced (although that can be done Passively with resistors and diodes)

The day someone makes a medium voltage Ultracap will be great. if just a single capacitor could store 60volts then that wouldn't need balancing. Thing is have a look around - you will be lucky to find even a 1Farrad capacitor that can store 60volts!

p.s. your English is clear, no worries. What is your native language?

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Joined: 02/22/2009
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Re: super capacitors

colin9876 wrote:

Ummm not really, the following reasons

1) Mains electricity is AC (not DC)
2) They dont make high voltage UltraCaps yet - They are all about 2.7volts (and ones that are 5.4v are made out of 2 x 2.7v etc)
3) You can buy high voltage capacitors but they only store small (microFarads) energy
4) I would never use high voltage capacitors in the >100v range, very dangerous
5) I dont think the problem with BMS systems is any lost energy from the charge source - the problem is they can be complex. Even strings of capacitors need to be balanced (although that can be done Passively with resistors and diodes)

The day someone makes a medium voltage Ultracap will be great. if just a single capacitor could store 60volts then that wouldn't need balancing. Thing is have a look around - you will be lucky to find even a 1Farrad capacitor that can store 60volts!

p.s. your English is clear, no worries. What is your native language?

1) of course main electricity is AC ;-) but it's not difficult/heavy to change this, don't you think so ?
2/3) I saw now there is no high voltage ultracap, but tomorrow ?
4) my idear was just to charge immediatly without a monstruous charger and, after, to convert this to a lower voltage. And, also, be abble to transform again the same voltage in an other one so you can use voltage or current. This just an idear...
5) OK: I was speaking about classic BMS, not capactive. This because I build BMS kit from "TPPACKS" and I had often problems with heat. So I bought a (built) capacitive BMS . That's works except ... it consumes when motorcycle is off and it's better disconnect BMS during winter ( see my blog http:\\www.motoelectrique.unblog.fr ). And no possibilty to increase voltage (it would be interesting to set in 72V instead of 48 but, if so, I will have to change again BMS). I was thinking it would be better with "classic batteries" like capacitors (if capacitors direct high voltage of course)

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Joined: 10/23/2008
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Points: 289
Re: super capacitors

Hiya,
I was trying to guess what country you are from, and from your blog I see your native language is French? Une Belle Langue.
Aixam make those electric Mega Vans in France dont they? Ive always wanted to get one of those!

Yes you are right that AC can be rectified to DC but thats really what chargers do. You seem to think they are 'inefficient monsters' (haha) but really chargers are around 80% efficient. When they drop the voltage you get most of the energy conserved by having bigger current so not that much is wasted.

Anyway I hope you are right that higer voltage Ultracapacitors come soon!

A Bientot mon ami !

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Joined: 08/03/2010
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Re: super capacitors

The short answer is that Capacitors can't deliver the total quantity of energy that other batteries can. What makes the Capacitor great is it's ability to charge and discharge almost instantly... but Capacitors are actually heavier than lead acid batteries based on energy.

The fact that batteries absorb and release energy relatively slowly is actually a good thing.

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Joined: 11/15/2010
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Points: 27
Re: super capacitors

Supercapacitor research was a very good thing in the old lead days , Lead battery suffer a lot if you ask high current , they invented the supercapacitor for shaving off the spike and allow the lead battery to work at constant current ... but now all this is past .. they invented Lithium battery that can deliver high current without capacity reduction.

If you have an old Lead EV adding a bank of supercapacitor can be a nice MLU (Middle Life Update) to extend the live of your battery pack and have a little bump in performance. Investing 300-400\$ in supercapacitor can give you a little more boost without the weight of extra battery.

But if your budget is more than 2000\$ is better to consider Lithium battery as partial or total replacement for the old lead pack.

If you are talking about a new vehicle there is no option , Lithium. Capacitors are almost surpassed even in the power density by the last Lipo , not talking about Energy Density and Price ,Lithium have a lot more energy and are a lot cheaper.

About recharging ; today the limiting factor is the infrastructure, not the battery , modern Lifepo4 or Lipo can charge at 1C , a typical car have about 20-30 Kw/h battery , recharging this battery in less than 1 hour is something that infrastructure cannot hold , so supercapacitor are useless also in this field ,

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Joined: 10/19/2011
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Re: super capacitors

It makes me very tangled. Only tried to know is reasonable.

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