Ultracapacitors: how to?

[Dui ni shuo de dui]

Hello everyone,

I've seached a little bit on this forum and did not managed to find any interesting information regarding ultracapacitors yet, so I've decided to create this topic, which hopefully will help me among with other interested people to gather as many information as possible on this technology.

I currently own an electric "big scooter", with 72V 50Ah lithium battery, 2000W QS motor and 72V 150A Sabvoton controller, and, while this setup is quite nice already, I would like to improve it a little bit, maybe by adding some ultracaps.

The idea is the following:
Currently, under big load like a full throttle acceleration, I can see the voltage going down from approximately 78 V to 70-71V. I assume that this is due to the internal resistance of the battery cells themselves that may not be able to provide sufficient current, probably because of a low C rating. The voltage goes up and remains stable while the scooter is speeding up.

I assume that, if I can find a way to buffer some electric power in between the controller and the battery, It should prevent this voltage drop, thus increasing performance and battery reliability.

The idea I have in mind is to use High charge/discharge rate components, and the ultracaps seems very appropriate to do this. Basically, I suppose I should place some ultracapacitors somewhere in between the battery and the controller, but I feel like it should not be just that simple.

For instance, after the ultracaps are being discharged, they may try to draw current from where it's available, ie: the battery. Since their charge rate is very high, they will ask the battery for too much current so I guess that there should be something for limiting this supply.

Anyway, I do not have any clear idea on how these things should be properly integrated. Would someone in this forum be kind enough to explain it to me? Any documentation, schema, picture, tutorial or whatever would be very much appreciated

 

[Punx0r]

I would try the search here for "ultra capacitors" to get the long explanation of why they have no purpose in a small EV. Maybe in the future when the energy density is 100 or 1000 times better

In short, the required capacitor pack bank will be so large, heavy and expensive you would be desperate to just buy a better battery instead. If you want to do the sums, imagine a capacitor bank in parallel with your battery and charged to battery voltage (78V) during high-throttle usage, energy is drawn from the capacitor bank as well as the battery, the energy in the cap. bank must be sufficient to keep the voltage >71V.

Even then, do you actually have a problem with your bike? Is the current draw on the battery known to in excess of its C-rating? Is it getting hot? Is the reduction in voltage (sag) causing an intolerable loss in top speed?

 

[major]

https://endless-sphere.com/forums/viewtopic.php?f=6&t=7511&p=124137&hilit=Ultracapacitor#p124137

Good research on the subject by a friend.

 

[Hillhater]

This was posted on another thread by the beastie .
http://youtu.be/8TkwoHgkuR0
You may find it interesting/amusing/scary !
I cannot decide if the guy is a wind up or a genius ?
Check out some of his other vids also

Oh , and Dui, if you are getting 8volts sag at under 3C discharge,... You should be looking at a better battery.
Or maybe, try a hybrid pack with some strong 65+C Lipo in parallel to stiffen up the discharge.
It will be a lot less bulky, expensive, complex,...than trying UC's !

 

[999zip999]

72v 50 ah battery ? A little more info on the battery. What is your amp draw ?

 

[Dui ni shuo de dui]

I would try the search here for "ultra capacitors" to get the long explanation of why they have no purpose in a small EV. Maybe in the future when the energy density is 100 or 1000 times better

In short, the required capacitor pack bank will be so large, heavy and expensive you would be desperate to just buy a better battery instead. If you want to do the sums, imagine a capacitor bank in parallel with your battery and charged to battery voltage (78V) during high-throttle usage, energy is drawn from the capacitor bank as well as the battery, the energy in the cap. bank must be sufficient to keep the voltage >71V.

Even then, do you actually have a problem with your bike? Is the current draw on the battery known to in excess of its C-rating? Is it getting hot? Is the reduction in voltage (sag) causing an intolerable loss in top speed?Good research on the subject by a friend.

Sorry for my late reply guys, quite busy days...

Actually, I've already searched on the forum before asking this question, but didn't find something that quite matches my idea. Most of the time, it seems like people just wish to replace entirely their battery with ultracaps, or wish to use the ultracaps for the full acceleration cycle, which, in my opinion, makes no sense at all.

Basically, in my opinion, the ultracaps should be used maybe 2, maximum 3 seconds during a full throttle acceleration, then usually the battery is able to keep up because while the motor revs up, it doesn't need much current intensity anymore, but higher voltage instead, which the battery is generally able to supply without much of a difficulty.

I don't have any particular problem with my bike, it works perfectly fine and has plenty of power, I just like to make experiences and see if I can build things even better. Building this machine has been a great experience and the result is awesome, so I feel like I just don't want to stop here

Oh , and Dui, if you are getting 8volts sag at under 3C discharge,... You should be looking at a better battery..

Well, given the cost of my current battery and the fact that I had to custom design it to make it fit the chassis, I dont' really want to invest in a new one
Besides, it is very hard to find reliable batteries with high C rating here, chances are that you may win the national lottery before you get your hands on a good one

Or maybe, try a hybrid pack with some strong 65+C Lipo in parallel to stiffen up the discharge.
It will be a lot less bulky, expensive, complex,...than trying UC's !.

That's probably a good alternative too. I would still like to try it with the supercaps because it has the advantage of very efficient energy harvesting during deceleration, but I'll keep this idea in mind too. Good suggestion.

72v 50 ah battery ? A little more info on the battery. What is your amp draw ?.

It's a LiFePo4 battery, 72V 50Ah, divided into two modules to fit in the battery. I have not made it myself but I found a factory here in China which made it according to my designs, so it would fit my scooter without having to modify the machine too much while keeping the mass center low. The amp draw should be around 150-180 amps continuous, the BMS is supposed to handle this, the manufacturer had to do it specially for me (thats what they told me at least).

I don't have much information about the cells themselves sice I never opened the battery yet.


What I think I would need first is a way to determine how much capacitance I would need to make this. I quite suck at math, so I don't really know how I'm supposed to calculate how much Farad I would need to achieve this.
Here are the hypothesis I have in mind:
Operating voltage at 80-72V
Current draw, between 150-180amps, (not sure if I should use the continuous rating here or the phase rating)
Time during the capacitors should be used: 2-3 seconds

Does anyone know how to calculate this? If possible could you give me an example of formula I can use so I can make my own calculations later using other hypothesis?

Thanks a lot to anyone who can help me!

 

[liveforphysics]

It's pretty easy to get a pack that handles more regen power than your tire can offer in traction.

 

[Dui ni shuo de dui]

It's pretty easy to get a pack that handles more regen power than your tire can offer in traction.

Fair point, you're absolutely right.
As said before, I would still want to give a shot to the ultracaps, just to see if it could work anyway, for my own curiosity (I know, I'm quite annoying )
Maybe I'll start another thread to discuss about the second lithium pack in parrallel, as it seems to be an interesting option too and I don't really want this thread to change direction.

So again, if anyone has a clue about the math who can help to determine how to dimension the caps bank, it would be really appreciated

 

[TheBeastie]

I have long held an interest in ultracap hybrid lithium battery setup as high discharge or high charge (regen etc) kills the total cycles of the typical ebike battery pack as shown in these tests and as examined in the threads discussion.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=73883
https://endless-sphere.com/forums/viewtopic.php?f=14&t=76048

And also because of just purely geeky interest in what a truly epic mega farad capacitor could do as future energy storage as it has somewhat limitless c-rate and cycles as pure capacitor design at its best is merely just storing/holding electrons instead of having chemical reactions to release energy.

I like this guys videos as he tends to show what is possible even with modest ultra capacitors available today..
https://www.youtube.com/watch?v=TdqskMl_rzI&feature=youtu.be

More here https://endless-sphere.com/forums/viewtopic.php?f=1&t=58684&start=100#p1152411

As for any real world work in ultracap on battery setups I haven't done any...
Only real work I have done was putting an xls style spreadsheet together a few years ago now on googledocs which anyone should be able to view and copy which has a breakdown of the farads,cost,total weight etc that would be caused by grouping a bunch of Maxwell Ultracapacitors together..
https://docs.google.com/spreadsheets/d/1sLe0sqyq33GyAzIIoaE8JWZOhbOO28GxlnNDwWlad3w/edit?usp=sharing
The data in the above spreadsheet might not be perfect as it was done to just get a rough idea of what to expect if I ever decided to create it..

 

[Deafcat]

seems to me, if you want off the shelf ultracaps they are going to take up a ton of space for the power you need.

time to build your own ultracaps

 

[TheBeastie]

I have read some of this stuff in articles on the web over the years but its been nicely stuck in one place on the wikipedia site in terms of using supercapcitors in EVs and racing cars etc.

https://en.wikipedia.org/wiki/Supercapacitor#Transport
https://en.wikipedia.org/wiki/Toyota_TS030_Hybrid

 

[Hillhater]

Toyota dropped the ultracaps after only 2 seasons and changed to Li battery tech instead.

 

[TheBeastie]

Toyota dropped the ultracaps after only 2 seasons and changed to Li battery tech instead.

If you want to cherry pick crap and fill this thread with unhelpful garbage because you don't like the idea of ever being wrong etc on top of going against the OPs original goals then fine, at least I will quote from wikipedia.

https://en.wikipedia.org/wiki/Supercapacitor#Transport
Quote "The supercapacitor and flywheel components, whose rapid charge-discharge capabilities help in both braking and acceleration, made the Audi and Toyota hybrids the fastest cars in the race. In the 2012 Le Mans race the two competing TS030s, one of which was in the lead for part of the race, both retired for reasons unrelated to the supercapacitors."

 

[Punx0r]

Err, so those teams are still using supercaps? Otherwise I don't get what your objection or point is...

 

[Hillhater]

Toyota dropped the ultracaps after only 2 seasons and changed to Li battery tech instead.

If you want to cherry pick crap and fill this thread with unhelpful garbage because you don't like the idea of ever being wrong etc on top of going against the OPs original goals then fine, at least I will quote from wikipedia.

https://en.wikipedia.org/wiki/Supercapacitor#Transport
Quote "The supercapacitor and flywheel components, whose rapid charge-discharge capabilities help in both braking and acceleration, made the Audi and Toyota hybrids the fastest cars in the race. In the 2012 Le Mans race the two competing TS030s, one of which was in the lead for part of the race, both retired for reasons unrelated to the supercapacitors."

Trying to give the OP the full picture, rather than the limited view of Wiki...
Reliability was never the reason for Toyota to switch to Lipo..

.....TMG technical director Pascal Vasselon has previously explained .......
......Toyota will retain the twin-axle kinetic energy-retrieval systems of its existing TS040 HYBRID but move to battery storage to allow it to move into the highest subclass of hybrid power that allows for eight megajoules to be deployed over the Le Mans lap.
"We feel we have to be in the 8MJ class; you can do that with a super-capacitor, but there is a downside on weight," explained Leupen.

 

[e-beach]

There are plenty of farad coulomb volt amp calculations out there....but little actual experience in super cap testing regarding e-bikes.

If you really want to know, as of this writing, for under $15.00 USA you can get enough 1F super caps and wire them together for a distance test. How far can you go on 1 Farad? Will it be enough to get you moving? Only a test will tell you.

 

[TheBeastie]

Err, so those teams are still using supercaps? Otherwise I don't get what your objection or point is...

Trying to give the OP the full picture, rather than the limited view of Wiki...
Reliability was never the reason for Toyota to switch to Lipo..

The thread is titled "Ultracapacitors, how to" and not "Ultracapacitors, why I shouldn't", the OPs first post is purely about wanting to overcome the challenges imposed by using super-capacitors and is not about posting pointless crap that everyone knows about why they have down sides, your empty points has been posted many times before, I just don't see why it has to be done again and again on this thread as like the others.
Yes ultracapacitors are a hard thing to do and is not cost practical, this is all about the geeky interest and challenge, if everything was about being the most cost practical the Bugatti Veyron and other luxury super vehicles etc would have not been made but sure enough they were..

Your posts are of trolling behavior, I pretty much believe you're behaving like trolls, and are pretty much post directly against the OPs clearly outlined topic of discussion. On a lot of other forums out there they would of been deleted as 'pointless/off topic'.

 

[Hillhater]

The OP seemed to be asking for as much info as possible, so no point in hiding the facts !
He might prefer to find a better solution to his problem.
But, im sure he did not expect a pathetic gripe over details in his thread either !

I've seached a little bit on this forum and did not managed to find any interesting information regarding ultracapacitors yet, so I've decided to create this topic, which hopefully will help me among with other interested people to gather as many information as possible on this technology.

 

[Dui ni shuo de dui]

I don't really want to start a big Internet fight, but I pretty much agree with what TheBeastie stated.

What I want is to find out how to do it, I'm pretty much aware of the issues/downsides of using capacitors and why this doesn't fit a high capacity application. But first, this is not for high capacity use, the only purpose of it would be to generate brief power burst during only a few seconds of the acceleration phase, and second I'm quite curious about how this could be achieved, even if I don't get the results I expect. That's what some people call experience, trying stuffs and learn from them even if they fail and even if you knew they would fail bbefore even starting.

Putting a lot of capacitors in serie/parrallel is not a problem for me, what puzzles me is how to manage them. I don't really know yet how I can command those capacitors to release their power automatically at the right time, neither how can I charge them during deceleration and/or during low load phases. My knowledge of this part is a bit limited so if anyone has any idea or suggestion I can try, it would be welcomed.

At first, I have one question. lets say I have a bunch of condensors wired up in series to reach 80Volts. Condensers are 3 Farad. How much capacity does this represents in terms of Ah? Is there any formula that can determines this easily?

(I've red your post @ e-beach and it's a good suggestion to just make tests, but if I can at least calculate the very basics I could then select appropriate components and make a more relevant test, comparing the theory with whatever I get in the end. It sure doesn't cost that much but I'n no billionnaire so I cannot afford to waste money on condensers I'll only use once for testing purpose)

 

[amberwolf]

I don't really know yet how I can command those capacitors to release their power automatically at the right time, neither how can I charge them during deceleration and/or during low load phases.

wire parallel to battery then no n eed to do anytghing, is all automatic

otherwise need voltage converters, diodes, etc,. to pump engery back adn forth

Condensers are 3 Farad. How much capacity does this represents in terms of Ah? Is there any formula that can determines this easily?

dunno forumula but convert to joules tehn ah ithink.

http://www.justjoules.org/conversions.html

 

[Punx0r]

80V / 2.5V (per capacitor) = 32 caps.

If they are 3 Farads each, then the capacitance of the series string will be 3/32 = 0.09375 Farads.

Total stored energy of the 32S string will be 1/2 CV^2 = 0.5*0.09375*80*80 = 300 joules. A joules is one watt-second, so 300/3600 = 0.083 watt-hours. At an average voltage of 40V that's 0.0021 amp-hours.

But it gets worse... Your bike is limited to operating between 80V and 70V, so:

0.5*0.09375*70*70 = 230J

Total available stored energy will be 300-230 = 70 joules = 70 watt-seconds

Your bike will have a power boost of 70 watts for up to one second! Consider that compared to what those capacitors cost to buy, and the space and weight on your bike...

 

[flippy]

the problem is not even space, it's balancing. supercaps needs balancing just like the battery pack. balancing a 32S capacitor pack brings a whole new set of problems to the table.


i woud recommend getting a (small) shovel worth of nice nichi/chemicon low ESR capacitors at the correct voltage and build a single parralel pack with it in order to buffer the first heavy pulses needed to get the accelecration going.

that is WAY simpler, cheaper and more effetive the messing with supercaps.

 

[TheBeastie]

At first, I have one question. lets say I have a bunch of condensors wired up in series to reach 80Volts. Condensers are 3 Farad. How much capacity does this represents in terms of Ah? Is there any formula that can determines this easily?

LOL 3 farad? Why not expect to power your bike on 3 AA batteries?
The caps I was refering to are 350 farad.. over 100 times bigger.. And I consider these the entry level size.. The main reason its not a common setup is because if you bothered to refer to my capacitor spreadsheet you could have an extra whole battery pack for the same cost as a capacitor booster setup.. If it could be done for just a few dollars it would be very common setup.
Did you look at my spreadsheet? The maths are inside that.. just click on the cells to see the math inside.. its all common capacitor math..
https://docs.google.com/spreadsheets/d/1sLe0sqyq33GyAzIIoaE8JWZOhbOO28GxlnNDwWlad3w/edit
I have posted this URL above so many times but not a tiny bit of it seems to be utilized, can it anyone see it?

 

[Dui ni shuo de dui]

80V / 2.5V (per capacitor) = 32 caps.

If they are 3 Farads each, then the capacitance of the series string will be 3/32 = 0.09375 Farads.

Total stored energy of the 32S string will be 1/2 CV^2 = 0.5*0.09375*80*80 = 300 joules. A joules is one watt-second, so 300/3600 = 0.083 watt-hours. At an average voltage of 40V that's 0.0021 amp-hours.

But it gets worse... Your bike is limited to operating between 80V and 70V, so:

0.5*0.09375*70*70 = 230J

Total available stored energy will be 300-230 = 70 joules = 70 watt-seconds

Your bike will have a power boost of 70 watts for up to one second! Consider that compared to what those capacitors cost to buy, and the space and weight on your bike...

Big thanks to you Punx0r, that is exactly the kind of things I was looking for.
Too bad that the capacitance diminishes while putting condensers in series, I haven't thought of that.
Nevertheless, it doesn't seems too bad in the end, I think it might be possible to do something if I can put my hands on better capacitors.

Thanks again for your great help!

 

[Dui ni shuo de dui]

At first, I have one question. lets say I have a bunch of condensors wired up in series to reach 80Volts. Condensers are 3 Farad. How much capacity does this represents in terms of Ah? Is there any formula that can determines this easily?

LOL 3 farad? Why not expect to power your bike on 3 AA batteries?
The caps I was refering to are 350 farad.. over 100 times bigger.. And I consider these the entry level size.. The main reason its not a common setup is because if you bothered to refer to my capacitor spreadsheet you could have an extra whole battery pack for the same cost as a capacitor booster setup.. If it could be done for just a few dollars it would be very common setup.
Did you look at my spreadsheet? The maths are inside that.. just click on the cells to see the math inside.. its all common capacitor math..
https://docs.google.com/spreadsheets/d/1sLe0sqyq33GyAzIIoaE8JWZOhbOO28GxlnNDwWlad3w/edit
I have posted this URL above so many times but not a tiny bit of it seems to be utilized, can it anyone see it?

Hi The Beastie,

I just said 3 farads as hypothesis to have some formulas, the figure itself was irrelevant, I could have said 0.25 or 4567 F it didn't really matter to me since I'm not at a point where I've already purchased anything

I've seen your spreadsheet before but I do not remember it had the Watt per 3 seconds line at the time, which was exactly the kind of thing I was interested to know. I'm not sure it even had the watt line (and I wouldn't know what to do with it at this time since I didn't knew that Watts were actually meaning Watts per second). Maybe I should see an eye doctor, I don't know... XD . Anyway, it seems to be perfect for me to do some calculation, so thank you very much for this great help