Super Capacitors to extend range......
There are some very smart people that way in on "V". I am very interested to see what you think of this.
Why can't super capacitors like the ones sold my maxwell Technologies be used to increase the range of an electric Scooter.
You can buy these cap banks up to 56 Farad values at 15 volts. You could use these capbanks combined with a DC-DC converter to change the voltage from say 15 volts to 48, 60 or 72 volts.
You would charge the capacitors before you leave so you would be carrying more energy with you. As your batteries decrease in value from say 66.5 for a 60 volts system the DC-DC converter could be tuned to say 63 volts. When the voltage dips to 63 volts the batteries and the Capbank now would be supplying power to the controller.
Also, caps are more efficent at storing energy than battiers which could be good for any on board solar applications that people may have on their scooters.
Why won't this work?
Because of energy density. Even the best supercaps available right now don't even come close to LEAD, let alone lithium.
I won't get into specifics again, but think of it this way: A mere 1Ah = 3600F. That little 56F supercap you listed would power my relatively small motor for approximately 1.5 seconds.
True, they are much more efficient than batteries when it comes to charging and aren't affected at all by the dreaded Peukert effect (only internal resistance), which is why EEStor's claims (how long's it been now?) look so good. You'd be set if you MATCH the energy density of lithiums, let alone DOUBLE it. Not to mention the fact that supercapacitors should have cycle lives in the millions.
Supercaps are good for acting as a buffer between the regen system and the batteries. Supercaps can be charged at very high current rates - so, the spikes in high charge coming out of a regen motor can be stored in supercap and then used as soon as you transfer from brake back to throttle.
Of course we're still waiting for EEStor to wow the world with their high energy density supercap...
It's my understanding (I could be wrong) but there is only a certain amount of space for energy storage, and lead/acid is still the most cost-effective medium for range.
I am very interested in integrating super-caps into the entire EV/battery/controller interface because they hold several specific benefits.
Lead/acid batteries should never be drained below 50%, or plate erosion during charging will significantly degrade battery life (very expensive to replace). Though super-caps don't hold a lot of energy per volume, they can cycle many thousands of times (don't need to be replaced).
Re-gen is not very effective because although chemical batteries can dischage very fast, they cannot absorb a charge very fast (I realize silicone batts are better than standard type lead/acid).
The benefit of adding a super-cap is:
Lead/acid battery life will be extended because initial accelleration and absorbing more of the available re-gen will be handled easily by a super-cap.
For an E-Scoot I envision five of the Green-Saver 12-volt batteries for 60 volts, and a super-cap about the size of one of the batteries.
Indeed, capacitors are better at absorbing a charge quickly for regen braking. But, remember, though, that when discharged, the capacitors voltage needs to be boosted with something. Capacitors' voltages are directly proportional to the amount of energy left in them. In other words, their discharge curve is a straight line at an angle. So, you have to add the cost of a high power DC/DC converter to the capacitor, otherwise only the top few volts of the cap are going to do anything.
Honestly, though, if you can afford a supercap the size of a 35Ah GreenSaver, then I don't thing you need to be using lead at all ;).
Alas, LinkOfHyrule is right. I did a quick calculation and the 10AH 36V 8# Li battery that takes me 15 miles round trip to work produces 1,296,000 Joules of energy. And my controller is fed voltage between 38V down to about 32 at the end, a decrease of 16%(360WH) A 56F capacitor has this much energy in it at 15 volts, Energy=1/2*C*v^2 or 1/2 of 56*(15^2) or 6300 joules. Dropping down to 16% less would be 12.63 volts the remaining energy is 1/2 of 56*(12.63^2) or 4468 Joules. Total, recoverable energy out of the super capacitor if used in my application is 6300-4468=1832 Joules. It will take 707 times the energy of this one 56F 15V capacitor. In order to fit 707 of them into the space and weight of my present pack which is about 120 cubic inches and weighs 8 pounds, your 56F 15V capacitor would weigh 8 pounds (3632 gm) divided by 707 or 5 grams. It would occupy 120/707 or 0.17 cu-in, this is about the size of an AAAA cell. This is probably two or three orders of magnitude smaller than the actual 15V 56F super cap. If these things cost a dollar apiece then it would be about what I paid for my present pack. But here I see the rebuttal "We can just get a handy dandy inverter to boost up the voltage. Think about what this inverter will be asked to do. 40 amps output is no teeny inverter, add to that you are asking for it to deliver this with an input source that can be high, let's say 36 volts, and yet also work while the input voltage goes down, to say oh 2 volts? Same thing for the regen issue, batteries can't take the amps? how about lugging around a 150 amp inverter for that occasional panic stop. Also same voltage range problem, dump 150 amps into a 150F capacitor for example. it will bring it's voltage up from 12v to 15v generating 1/2*150(15^2-12^2)=6075 joules or 1.68 watt hours, about 0.5% of capacity. Need to boost the voltage to get efficient use of the capacitor's ability. Another problem is what capacitors do when voltage limits are exceeded. I'm sure all have seen an exploding capacitor, and those were tiny capacitors by comparison.
So go out there and solve these problems. I am going to be so happy when all of the above rant is irrelevant. I am tired of wet chemistry, smelly H2S and finicky BMS and chargers. But this is kicks, I'm havin a ball evolving from smelly hydrocarbons, dinosaur sludge and global warfare. All we can do is......
I've seen the Mini. Very nice. The capacitors do about what I expected: crazy discharge rates for accelleration and presumably a place for regen braking to go.
"To the left you see a pair of MAXWELL pulse discharge capacitors, rated at 7.5kV, 36uF (1kJ) each"
o_O You're going to need a pretty specialized converter to have that 7,500V usable!
Good for rail driver/wire exploder/coin shrinker, though...
Hopefully the title will draw a few enthusiasts that know a lot about capacitors.
A while back I read a delightful book called "Draw the lightning down". It covered the history of electrical experimentation, and was filled with very interesting stories.
Capacitors were a fun toy a long time before chemical batteries. Amber (petrified tree sap) could be rubbed with wool and a static charge could be played with. The amber (and later sulfur) were dissolved and re-cast in balls or discs that were spun while being rubbed with wool/fur. A Leyden Jar is an easily and cheaply built capacitor, and is charged by the static generator.
Benjamin Franklin not only made useful discoveries, he was very good at constucting repeatable experiments to discern and explain the characteristics of electrical phenomena.
The jar was made from thin glass and the outside bottom half was coated with a metal foil. It was filled with water and a rubber stopper was put in the top with a metal rod that passed through the stopper to the water. While the outer foil was touched to a metal drain pipe (literally to "ground") The spinning generator was touched to the rod by a wire.
Once the jar was charged, the water could be poured out (it was only a conductor). A negative charge on one side of the glass was electro-magnetically held there by the positive charge on the other side. You could re-fill it with water and discharge it weeks later.
If the water, plug, and rod were left in, you could shock someone by having them touch the rod and foil, which would allow the two sides to equalize.
When looking at large supercaps, it appears the voltage can be tailored. It appears there are layers of conductive foil separated by insulative layers, then rolled up to make them as compact as possible. Is there a series/parallel arrangement to the insides to get a certain voltage?, perhaps the type and thickness of the insulative layer?
Simple capacitors are easy to make (certainly low capacity, though) , but I'm just curious if anyone knows what the insides of a brick size of capacitor is like concerning the materials and configuration?
Li-ion’s with super-caps
more Li-ion’s with super-caps
capacitors in hand tools
Chinese E-Bike with capacitor instead of battery
Thanks for all the links spinningmagnets'
As you pointed out, the capacitor came along before the battery, I guess that's so. And it took all these years for capacitors to finally take off. And Batteries have come a long way too. Right now the battery is king but can probably get some help from capacitors. Look at the name of this thread. Capacitors to extend range... At the moment the job of capacitors is to make life easier for batteries by smoothing out the bumps. Well that is exactly what batteries do for the IC engine in a hybrid car isn't it? But I don't really think there is enough energy storage in capacitors to make a big dent in the range just from that, at least not til EEstor comes through. There will be incremental gains due to less strain on the battery though, remember Peukert.
There is hope for capacitors I think. Yesterday I said that buck boost DC/DC converters were not here yet. Well I looked around and they aren't that far off. I found one that could convert 4 to 36 volts in to .8 to 10 volts out and supposedly up to 20 amps, probably peak. But hey, that's getting there.
Then I was reminded of Manzanita Micro's amazing PFC line of EV battery chargers which can pump gobs of amps (up to 50 actually) into big EV Lead from 220VAC. Rich if you're out there, When will we be seeing a PFC 150 that can take in DC from Capacitors at maybe 1500VDC and put out any DC voltage you want at hundreds of amps and then be reversed to fill up those caps instantaneously. I'm quite sure with enough smart people working on it, it will happen.
All the wonderful links and posts found here and the internet in general catalyzes the process.
I'm just blue because I don't really have the money or spare time to persue these experiments. I am already awash in stuff I tried that became obsolete.
"A Leyden Jar is an easily and cheaply built capacitor, and is charged by the static generator"
I can't believe I didn't make that connection before!
I'm gonna make a big capacitor out of a roll of plastic wrap and aluminum foil (just for the hell of it), but I've been to lazy to go to the store :P.
A123 Systems is selling some of their RC Car packs with an included DC-DC converter that raises the voltage slightly and keeps it constant. I think this is so two of their 3.3v nominal cells in series could match the 7.2v nominal that RC cars need, but it looks like it can also raise it to 10.8v. And it handles very high power. Its kind of pricey, but really innovative.
Exercise GREAT caution when making a "home-brew" capacitor.
For a short while (in the book I referenced) it became trendy to make a large Leyden Jar and to shock animals as a demonstration. All in the name of science, but the practice was quickly decried on grounds of cruelty, especially since the animals often died.
Benjamin Franklin was delighted at the demonstration where a large jar killed a chicken, then a smaller jar re-started its heart. This was just before the book "Frankenstein" (M. Shelley) and was considered cutting edge science. I was very suprised at references to defib in the 1700's...a drowning victim was defib'd, causing a raging discussion on the morality of bringing the dead back to life.
As long as we're on the subject...
To "batiere" is French for something along the lines of "beat", same place we get the legal term "battery". The French were early adopters of newer advances in mobile cannon, and the French artillery called a group of cannon a battery, because they beat down their enemy forts.
When storing cannon nose-down in the armory to prevent humidity pooling and rust, the ball at the back of each cannon (that was used to adjust the elevation) was the highest part. They were packed close together to save space.
Benjamin Franklin made many Leyden Jars out of the standard "round shoulder" medicine bottle, and the top of the central conducting rod was often capped with a brass ball.
Ben would charge up a tray packed with jars, that he could use over the course of several days one by one. He noticed that they looked like a cannon "Battery" that was in storage, and the term stuck, even though they were actually capacitors.
The invention of the chemical battery was closely tied to experimentation with the "torpedo" fish that could shock its prey or its enemies. Its body was a chemical battery that charged an internal capacitor.
Don't know how accurate these stories are, but, as Mark Twain (may have) said:
"Never let the truth get in the way of a good story"
Order that book from your local library, you'll enjoy it.
"Exercise GREAT caution when making a 'home-brew' capacitor."
Trust me on this one: I'm well aware of what a capacitor can do. If you've ever seen a wire explode or a coin compressed by sheer inductive force, you make SURE you handle those caps like your life depends on it; because if you're not careful, it just might.
Besides, I don't have anything on me to charge it up with, anyway. 'Cept maybe a camera flash...
A fun page on homemade capacitors
Since I have seen e-bikes and hand tools that use only capacitors (short range, but instant re-charge. never need to replace caps) there must be a way to regulate the current coming out of the caps.
Have any of the resident electrical gurus seen the schematics of cap-tools?
I have never seen anything use only capacitors. Where?
Grandpa Chas S.
capacitors in hand tools (only one of many sites)
Chinese E-Bike with capacitor instead of battery
how to make a better capacitor “shake-charge” flashlight
As an armchair engineer with clean fingernails, I "think" a capacitors easy absorbtion of electricity would not cause regen resistance the way a motor in regen mode would. As you've indicated, when it's charging a chemical battery, it can actually be used as a brake (more effective in heavier vehicles). That is, until the cap is full, then the regen is trying to pump energy into the battery.
Just a guess, I'm hoping someone with more EE education will fiddle with this and post the optimum configuration.
Thanks for the links they were interesting.
In a nut shell the article is saying the power density is far too low for the ultra capacitors to be anything more then a help to batteries. There is still a long way to go.
I am sure that whitout using supercap as buffer in EV isn't possible to make a EV as a mass dealing.
but the supercap can also be a very good performance enprover in a hybrid veichle, acting as a KERS;
by have a carefully to place It in a freewheel driveshaft!
Handling a power peak from a regenerative breaking in this very efficient way, means extend the range of battery
at the same way, you also handling a launch assist power peak call.
It result an very long extension in a BATTERY LIFE!!
BE SURE, WHITOUT THIS TECH, THERE IS'T FUTURE FOR EV!
Waiting a zerofilo-bus that recharge a supercap every bus stop in the town!
I'm chasing down these puppies... Super-Cap + LiFePO4 hybrid battery...
You can actually get these hybrids here in the states
Here is a link to a retailer who has them available = http://www.electriccarpartscompany.com/Hybrid-Super-Capacitor-Batteries_c_63.html
The specs you will see that will jump out are the 5000 cycle @ 80% DOD, The low weight, and the amount of juice these guys can withstand which make them suitable for Electric drag racing applications if you have yourself a light ride!
To my knowledge nobody here in the states has performed a 5000 cycle test run not tested them on the strip as of yet. There are a few people that have stepped up to say they will test them soon but until then they are unproven.
There are also domestic options Ioxus makes a hybrid cell similar but with even better cell characteristics they can be purchased as well. Here is the link = http://www.mouser.com/ioxus/
There has been a successful EV dragster that holds an NEDRA record at the moment which ran completely off a Maxwell ultracapacitor bank! The car was built by BYU students. Here is a link to check out and learn about how they pulled it off = http://www.altenergymag.com/emagazine.php?issue_number=04.04.01&article=dragster
Now there has been much research done on this and the results are positive using an Ultracap in conjunction with a battery. The ultracap can help extend battery life by leveling out the peak loads. There is a lead acid battery that has been developed that adds an ultracap in it to extend the life and reduce weight similar to what they have done in the lithium variants it is called the ultrabattery! They integrate the ultracap on the neg terminal of the battery to achieve better peak leveling.
The (ERT)Electric Reverse Trike I am building will employ a hybrid system so soon I should be able to have some good notes on it for you guys. I hope the links were helpful :-)
Take care gang,
Great info! I've got a couple of spare Vectrix vx-1, that run fine, but the batteries are going bad. I'd like to be able to capture more of the regen braking power than the 17% (+/-) claimed.
I'm extremely interested in your reverse trike project. I've got one going myself. My brother (an engineer from the Viking cars team in Bellingham WA) and I build one "way back when" we were in college at Western Wa Uni. It was a very impressive car in it's time.
I'll PM you on that note.
Gosh, maybe I should consider Ultrabatteries (lead-acid), and a cheap solution for the moment... I wonder if the charging profile of LA can work based on the LFP profile. In my previous experiments LA batteries tend to charge OK at just about any other battery's profile.
I would have to disagree with you on this one as I do not believe that EV are in the hands of the Ultracap. However the new Graphene ultracaps that has 20 times the current energy capacity levels sure would help push the electric cars along much quicker :-) When they decide if they decide to manufacturer them they would be a game changer for sure I believe. There is also the Zinc Air we keep hearing about and is currently being used in bus fleets for testing seem promising however trying to get them to adopt this technology and retrofit the necessary support structure will take a long time to adapt I am sure if ever. The switch from the ICE and fossil fuels is inevitable and Electric technology is really beginning to gain momentum. The key is with the battery technology and its affordability. I think for more widespread adoption the battery needs to have a better performance than our lead acid work horse and the price point needs to be around $100-125 per Kwh. If we were able to get a battery that weighs roughly half of lead acid, can be discharged regularly to 80% levels, can be cycled 500 times or greater, and the cost is around $100-125 per Kwh than we would see many more electric vehicles on our streets :-) The time is soon approaching yet it seems so far when we are stuck at $500 per Kwh for Lithium variants or even worse for lead acid when you factor in replacement packs over the course of a 12 year span! Its not easy being green but somebody has to do it :-)
Take care Sangali,
ya you can PM me anytime and that is funny you brought up the Viking project I was just reading one of my books this evening all about the cars :-) It is one of those oldie but goody books LOL! The book is called the New Electric Vehicles A clean and Quiet Revolution. It is amazing what you can learn from the old books! So ya we will have to share notes I am more than happy to share my knowledge and experiences when ever I can. The more Successful EV we get on the roads the sooner the better :-)
Catch up with you soon,
... and on a related note: I played around with Zinc-Air batteries used for ocean shipping buoys. These are relatively high discharge rate and high capacity units. Basically Zinc-Air just can't deliver the juice unless you really bank them up -- which is OK for large vehicles like busses and trolleys. I did a lot of experimenting with Zinc-Air medical batteries in 9V radio battery form factor, and also with some custom ones used to recharge cell phones and run consumer camcorders out in the field. I used electric helicopters and banks of 12v auto lightbulbs to test with. No configuration would suffice. However, Lithium-Air, and Aluminum-Air look pretty promising.
I've been checking into Graphene super caps, I've got the stuff coming from China to make the super caps (electrolyte and graphite-oxide), I'm going to try the LightScribe method. I think Graphene is the most promising technology on the horizon. Too bad for Envia & GM... I'm betting that by the time their batteries hit the market, far better products will be right on their heels, less expensive and just as good/better using Graphene.
Not sure if this was discussed yet...
Pulse Width Modulation works both ways.
0% throttle means 0% "pathway" from battery to motor.
50% throttle means 50% "pathway" from battery to motor.
100% throttle means 100% "pathway" from battery to motor.
Regen occurs when motor speed exceeds "apparent" voltage as seen through the eyes of PWM.
What this means is that when you rapidly close the throttle the "pathway" gets closed off in the reverse direction and the regen current gets wasted by being trapped on the motor side of the controller.
Where Supercaps make sense is to provide a buffer "aside" the controller so that when excess energy builds up on the motor side during regen it can have a place to go. When you open the throttle again the first thing you do is open the Supercaps in order to empty them.
As it stands now regen is wasted as you drop below 50% throttle. (technically 50% "duty cycle")
So there is an authentic usefulness for Supercaps, but they are to solve a very narrowly focused problem.