# Ultracapacitor based power system



## dcb (Dec 5, 2009)

V6imp said:


> If it works out too expensive, ends up too large a setup and proves unable to give the required power time without falling back into the first 2 points, it won't happen.





V6imp said:


> Any ideas?


You said nothing about what the budget, performance or space requirements are. So yes, I have ideas.


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## V6imp (May 20, 2015)

Hi, thanks for responding, basically, as cheap as possible but I suppose upto £2000 being realistic. Power, I'd like to 150ft lbs + of torque but more the better and it's to fit in the front of a Hillman Imp but it's a spaceframe car so packaging shouldn't be too much of a problem. I've got plenty of engineering gear handy so building bespoke parts isn't a problem either. Not really looking at buying the latest gear off the shelf, more into making as much myself with reliable components on top. 
Many thanks, Mik.


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## Hollie Maea (Dec 9, 2009)

You would probably be better off using batteries. A pack that was oversized to accommodate the power needs would probably still be cheaper and lighter than caps. And loads easier to work with.


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## nimblemotors (Oct 1, 2010)

LiPo Batteries would be cheaper and lighter, but they would not last very long.
Supercaps have about 1 million cycle life. Lipo maybe 200. A123 M1 cells are the best choice for power and cycle life, afaik.

I have a set of supercaps that can put out 950hp...for 2 seconds,
and it can do it over and over and over again.
Look at F1 cars, a flywheel might be a better choice, but isn't cheap either.

You can't beat Nitrous Oxide for short-term power increases for an ICE.


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## dcb (Dec 5, 2009)

each 1000 farad of 2.7v ultracap can deliver basically 1 watt hour. 
746 watts in 1 hp. How much hp do you want for how long?

if you want 300hp for 10 seconds,
1 watt/hour= 360watt/10 seconds
300hp*746=224kw
224kw/360=622k farad worth of 2.7v cells.

3k farad cells are maybe $50 (not including any balancing/management, or a motor or a controller or??? balancing a pack in 10 seconds with 300hp is going to be serious $$$).

622k/3k * $50 = ~$10k, just for the caps themselves, pushed to the limit. Add a safety factor in there of %25, so $12,500. And another %15 for losses, so probably $15k.

This is an expensive hobby


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## Hollie Maea (Dec 9, 2009)

dcb said:


> each 1000 farad of 2.7v ultracap can deliver basically 1 watt hour.


Only if you drain them down to 0 Volts. Which has its own challenges...now you need some kind of boost/buck converter to give you a reasonably steady voltage output.


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## dcb (Dec 5, 2009)

yup, didn't want to get too wordy, file under ??? probably safe to say another %25 added to the cost of cells to keep the pack voltage at a reasonable level for boosting. And whatever a 300hp boost converter costs (or use a low voltage motor with a high voltage controller if they both can handle it)...


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## Hollie Maea (Dec 9, 2009)

nimblemotors said:


> LiPo Batteries would be cheaper and lighter, but they would not last very long.


Like I said, oversize the pack...use 30C cells and make it 4 times as big as you need so that you can do your 30 seconds, discharging at 30C but only a quarter of a cycle. Stay away from the edges of the SOC and the cycle life goes way up. Like I said, you are still going to be way lighter and cheaper with an oversized pack.

When it wears out, replace it with the money you didn't spend on ultracaps.

Or hell, use Lithium Titanate to get your cycle life up. They are the heaviest and most expensive of Lithium chemistries, but still way better than Ultracaps.

Ultracaps sound great, but they never pencil out.


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## dcb (Dec 5, 2009)

even with a battery pack that can handle the discharge rate @ voltage...


V6imp said:


> I suppose upto £2000 being realistic.


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## nimblemotors (Oct 1, 2010)

If the pack is now 4 times bigger, it will be 4 times heavier, and 4 times as much cost still only last 4 times as long, 200 * 4 = 800 cycles, ok, I'll give you 10,000 cycles, it better be 100 times cheapeer $20k in caps, you won't do $200 in batteries. 

Fact is these cars don't need to last long, as someone spends a lot, shows off a little, makes a video, then the car is mothballed or dismantled or a garage queen. How many miles get put on a Koeseennngiingnngngnneeon



Hollie Maea said:


> Like I said, oversize the pack...use 30C cells and make it 4 times as big as you need so that you can do your 30 seconds, discharging at 30C but only a quarter of a cycle. Stay away from the edges of the SOC and the cycle life goes way up.  Like I said, you are still going to be way lighter and cheaper with an oversized pack.
> 
> When it wears out, replace it with the money you didn't spend on ultracaps.
> 
> ...


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## Hollie Maea (Dec 9, 2009)

nimblemotors said:


> If the pack is now 4 times bigger, it will be 4 times heavier, and 4 times as much cost


Four times bigger and more expensive than what? Remember, we are comparing to ultracaps.

Let's see. Maxwell has a "high energy" cap for sale. It's rated at 2.85V and 3400F. Let's pretend for a minute that we can use its energy down to zero volts (we can't, but let's be generous). That means we get a whopping 3.8 Watt hours out of it. It weights 520 grams, so the energy density is 7.3 Watt-hours per Kilogram.

A123 cells, just to grab a random example, have an energy density of 130 Watt-hours per Kilogram. So you could oversize your pack almost 20 times before it gets as heavy as your ultracaps. At that point, you aren't really even doing cycles--only using 5% of your SOC. And since the battery is so oversized, it's not even getting warm. They'll last forever.

Let's see, you can buy those caps for $70 a pop. That's $18,400 per kWh. You can buy a lot of batteries for that...


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## Tomdb (Jan 28, 2013)

What kind of racing will you be doing with this car? Or is it just a road car?
Dependent on the kind of racing you can determine the cycles you will be running, thus make the choice between "caps" or "batteries" a more informed one.

2000 pounds for both the motor and energy storage and other components?

200Nm, where in the drivetrain? At the wheels at a differential?

Also speed rang you want to operate at, this will determine the gearing and eventually the motor choice.

What kind of weight penalties can you live with, remember this will involve sourcing uprights with cv joints and shafts to match. Most likely a weight penalty of at least a kilo or 15-20 to start off. So if you say that a 100kg weight penalty is acceptable, with a proper budget this is do able.


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## V6imp (May 20, 2015)

Looks like the caps idea is a non starter then. What I'm looking for is a usable boost in power which is switchable, reusable and more practical than building a full race engine as it's a road/sprint car. The easy option would just to supercharge it but it's been done and I'd like to explore different options. 
Weight is also important as if the overall package is too heavy then my power to weight ratio will drop below the non assisted setup. On the plus side, with batteries, I can run for longer periods of time under full power and with near permanent 4WD.


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## Karter2 (Nov 17, 2011)

It sounds like you are building a track car ( space frame Imp ?) ..
..Hillclimb maybe ?
Either way , I guess you are more concerned with weight, power, and cost, rather than niceties like cycle life or reliability !..
So, cheap, light, powerful RC Nano tech LiPo (as used by many EV Drag racers), would be the obvious choice.
If you only want 150ftlb for 30 secs, you don't actually need much battery.....2kWhr would probably do it
200v ,10Ahr of 90c LiPo
But even with those, I'm afraid your budget will have to multiply several fold !
Oh , and forget the regen, that will force you into AC drive systems that will multiply the costs further


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## Tomdb (Jan 28, 2013)

If you want a proven battery pack technology look at this site
http://www.ampahaulic.com/

For a motor, you would have to decide to go with one motor and diff or two separate motors. 

I would personaly go for one of the EMRAX motors
http://www.enstroj.si/Electric-products/emrax-268.html

However, these start around 5000 euro with out controller so are quite pricy. However the power to weight ratio is insane.


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## V6imp (May 20, 2015)

Well, the technology is there I guess, but it's spiralling way out of any useful budget. As I first posted, it's only a paper exercise at present just to look at the viability of the project. By the looks of it, I'd be better going for a switchable mechanical 4WD system. The cost of everything would far exceed the cost of even a sequential Sadev gearbox, similar to what was found in a Metro 6R4 or RS200. Guess for now, I need to bow my head in defeat. 

The car is a spaceframe due to the floor being rotten and with the intended V6 layout, it was just easier and more practical to start from scratch with the chassis. The original car was only 875cc with the engine in the rear. (Hillman Imp Californian coupe ) 
We've got a few spaceframes on the go, the Imp, a Ford Sierra and a Ford Escort estate with a couple of restorations too. Had really hoped that the electric idea would pan out but hey ho, if you don't dream, then we'd still be living in caves 

Many thanks to you all for your input, greatly appreciated. I'm not done with electric though, but I'll start thinking of a new EV design with battery only power. 
Hmmmmm, now what could I put it in


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## Karter2 (Nov 17, 2011)

Are you building a track/strip or street car ?
That Imp with a Warp motor hung the back and a few kWhrs of LiPo might just make a hot 1/4 mile EV. ,
( learned to drive in an Imp !......first car I wrote off was an Imp !! )


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## V6imp (May 20, 2015)

It's primarily a road car with the occasional strip/track action. It's already got enough power planned with the 3ltr V6 but power is addictive and the idea of a 4WD system just takes up so much space inside the cockpit hence the idea of a small separate power unit up front. 
When the build begins in earnest, I'll post a link for those interested in the build. 
Thanks again to all those who provided the time and info on my theoretical whim 
Mik


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## Sunking (Aug 10, 2009)

LiPo should work and likely the better solution. If you buy from HobbyKing cyycle life would be an issue, but if you buy quality LiPo packs cycle life should be up around 500 to 750 cycles. Not sure if that is enough but pretty closely matches Chi-Com LFP cells cycle life. 

LiPo would be less expensive, lighter in weight, and take up less space. I think the drag racers use LiPo because th eenergy density is high, and C-Rates on Lipo is extremely high up to 100C continuous if you can afford it. 50C is common.


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## mizlplix (May 1, 2011)

Everyone is ignoring the real Cap problem, super, ultra or not....self discharge rate....high.

Charge an ultra cap and any Lithium battery. Wait a month and test. A real eye opener.

miz


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