supercapacitors instead of batteries in electric cars

I think there is a lot of criticism because a stacked unit was described, and that stack may have been made to test the voltage rating of the separators.

I think the actual modules were only an inch or so square and 2230 or so were stacked, possibly all in series, specifically to test the density and the rating.

Production modules of 120 and 240 volts would be much more useful and marketable, plus maybe

12 volts and the new auto voltage of 42 volts.

Ultracapacitors will be improved, and they are already amazing.

Joe Fischer

AZ Nomad writes in article dated Fri, 13 Oct 2006

23:23:32 GMT:

dated Wed, 11 Oct 2006 20:20:54

-0400:

I'm talking about available power when not charging. For example, in an electric car, more power = better accelleration. With a radio transmitter, more power = longer range.

Supercapacitors provide better energy storage than capacitors and better power than batteries. That makes them a compromise. If it was the other way around, it would make them superior in every way and the traditional tech would be obsolete.

I know I wouldn't call something a "fuel cell" unless it held energy. If you like, you may read my use of that term as meaning fuel-cell-system-including-the-dang-fuel-storage-tank.

-- spud_demon -at- thundermaker.net The above may not (yet) represent the opinions of my employer.

dated Fri, 13 Oct 2006

23:23:32 GMT:

dated Wed, 11 Oct 2006 20:20:54

-0400:

Supercaps don't offer more power. Their internal resistance is terrible.

I don't know what terminology you are using, "ultracapacitors" have very little internal resistance, isn't that what allows them to be charged faster than batteries without harmful heating?

Joe Fischer

So you assert. Care to provide a citation of a cap capable of supplying 100 amps for 60 seconds and what its internal resistance is?

Did you just make those numbers up?

Their 300F part has an internal resistance of 6milliohm. .006 ohms is terrible compared to what?

Now, give it a rest...

tells about what he is doing, maybe you can convert the numbers to amps.

I have been seeing numbers like 4 watt hours per kilogram, and that can be compared to a car 12 volt battery of 50 amp hour.

The needed feature of the ultracapacitor is the high rate of charge without damage, not too much storage is needed, just enough to absorb the energy of braking, and some resistor circuitry to let the capacitors hold the DOD (Degree Of Discharge) of the batteries as small as possible to protect them.

The charge on the caps from braking down a hill could be allowed to bleed to the batteries over time so the energy will be available to climb the next hill.

Joe Fischer

... 100A for 60 seconds is 6000 coulombs = CV = 2.5C, so we need at least C = 6000/2.5 = 2400 F, ie 8 of these 300 F caps. They would store 1/2CV^2 = 7500 joules.

Discharging them at 100A would waste 60x12.5^2x0.006 = 56 joules, for a discharge efficiency of 100(7500-56)/7500 = 99%. Not bad, even when multiplied by some charge efficiency.

Nick

Joe, I have only recently become aware of this thread. Since I have been looking for answers to the problem of regenerative braking in a 144 Volt DC system, I have hit the brick wall for ways to harness it. I am ignorant to a controller that can adequately control a converted S10 pickup with regenerative braking while using an Advanced DC motor at 144 volts.

In the alt.energy.renewable group we have been discussing the subject within a thread named: Hybrid cars and how come they do that?

Using the supercapacitors as you suggest may be the key! Maybe a relay that kicks over to the "save" mode when you push the "save button, or when your brake light switch is engaged. I can see a pot attached to the brake pedal to variably dump the energy into the capacitor before it hits the brake light switch. The idea of trickling it back to the batteries really needs to be investigated.

I read the statistics about the 300 F capacitors, and one thing bothered me. Please forgive me if I propose a concept that is undoable because of my ignorance, but... The capacitors seem to be 2 volt. OK -- I can live with that, but (as I understand capacitor theory) if we put these in series to accept 144 volts, our capacitance will be divided by 72 (or .0416 Farad) - not a good deal. Another problem -- if the capacitor voltage doesn't exceed the battery voltage -- I believe that no charge will transfer. Will

The bad news is, there may not be one off the shelf, but the good news is, it can always be added later, the cost of motor and controller make the project expensive enough.

At least part of that thread was crossposted here.

I think they are common on newer EVs and hybrids.

The batteries should be able to handle some braking energy, I think the big danger is overheating with fast charge. Fifty years ago it was common to jump start a car and take it to the gas station for a $1 fast charge, but 30 minutes would not be fast compared to braking time.

I suspect that is part of what the circuitry may do, but only down hill charge, if the controller can sense that. It is something to study until production lowers the price and makes them available in quantity.

It varies, but modules will be available, when your ship comes, check the last item in the last chart at

48 volts and almost 8kw per kilogram punch, but less than 4 watt hours per kilogram storage per module.

I think you did the math wrong, the 48 volt module is supposed to be 165 Farads.

There has been a car profile supercap offered on ebay listed as 2900 farad, but it may be better to just use the manufacturer listing of watts and watt hours for power and storage.

Most braking can be started sooner and last longer, spreading out the charge over a longer period of time, but I don't know to what extent that will help the heat and fast charge problem.

That is why flywheels, compressed and hydraulics with a trapped air accumulator have been considered for regenerative braking.

I thought I saw a kit for an S10 that should have a user's manual, maybe not.

Have you seen

or (possibly not timely)

and up to 750,000 more;

Joe Fischer

300 farads / 72 = 4.167 Farads.

If the hybrid is setup right with IC equaling cruise HP.... then the high power is only for a few seconds as you accelerate from a stop. Now someone is going to say they need storage for a Pike Peak run... if not then battery is only needed to crank the IC. And the capacitors carry the surge to the electric motors during acceleration.

It might be added that folks have been using 338F electric motor starting capacitors. And they are not far off what you would pay for a Diehard on IC's. The starter only runs 5seconds before the engine hits and the alternator takes over. Actually see auto stores selling them things for a batteryless jump start kit.

50years after custom car and chopper builders first installed them things as battery eliminators.

If you cruise by a power substation many of those babies start out out at

1megF and run all the way to 100,000megF at 100,000volts for 7ft x8ft x 7ft oil filled capacitors.

And many of the standard industrial DC motor are 300V and 600V....not

148volt....never saw a printing press,locomotive,or drilling rig traction motor that wasn't 600V. Many of the machine tooling DC motors are 300V out to about 75hp.

Some of your ceramics used on radars and high freg. applications are water cooled.,but smaller than utility power capacitors.

Unbelievable. Are you confusing "meg" and "micro"? :-)

Nick

================================================== With 144V peak avail for accel, one might cruise at 72V or less... when you start to coast, is the unloaded back emf going to be 72V? If you start to pwm this into a cap bank, it will start charging towrad 72V, but presumably, the car will slow down before it gets charged up. A DC to DC converter could boost the captured low voltage on the cap up to a voltage that could be used for battery charging. Might be easier to use the regen to recharge the 12V accessory battery thats running the fan and lights and windshield wipers etc. I asked if you could use a 2.7V boostcap to catch the regen from a 12V motor on the sci.energy newsgroup. The experts over there went into orbit. They thought I was a doofus from Mars. I guess I just couldnt ask the question in a way they understood. Go read the thread for a hoot.