Supercapacitor News

And then the energy stored in supercapacitors could also be higher with respect to normal batteries. Maybe we could have a Model S 500 KWh?

Electric700 said:

There was an article I found from late last year about an interesting supercapacitor development. Imagine being able to charge your Model S, powered by supercapacitors, in just 16 seconds! And they could last 27 years or longer (10,000 cycles).

More here:
Charged EVs | Graphene supercapacitor packs basketball court-size surface area into one gram

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Do you realize that to charge 85 kWh in 16 s requires around 20 MW of power... Do you realize how big the connector and circuitry would have to be?

Electric700 said:

No, I was just rephrasing from the article. Very good observation.

If you kept the connector and circuitry size the same as it is now, do you think we're talking less than or more than 15 minutes to replenish an 85 kWh supercapacitor depleted to 10% (about 30 miles of range left), so just about 75 kWh is needed?

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Current is the limit. With current battery voltage (tops out just below 400V) the current connector can handle probably 135kW so 330A. So at that voltage at least 30 mins for 85kWh. If the voltage was much higher in the supercap then sure, but then the car would have to carry a heavy and ineffcient transformer OR they'd have to create a drive unit (motor+inverter) that operates at much higher voltage. Hard probably.

IMO capacitors are AC charged not DC charged. The charging circuitry would completely different with respect to that now in use on the Model S for Supercharging. With capacitors the higher the frequency of the input voltage would be the faster the capacitors would be charged.

Raffy.Roma said:

IMO capacitors are AC charged not DC charged. The charging circuitry would completely different with respect to that now in use on the Model S for Supercharging. With capacitors the higher the frequency of the input voltage would be the faster the capacitors would be charged.

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Eh.. No? http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html

The current charges are also DC, and could probably provide more current, but not safely given current li-ion tech.

Raffy.Roma said:

IMO capacitors are AC charged not DC charged. The charging circuitry would completely different with respect to that now in use on the Model S for Supercharging. With capacitors the higher the frequency of the input voltage would be the faster the capacitors would be charged.

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No a capacitor is just like a battery like that: DC in - DC out.

Doug_G said:

I suspect Raffy was confused because of the fact that capacitors conduct AC current but block DC current. But we're talking about small value capacitors used in applications such as filters, decoupling, DC blocking, etc. Capacitors can only store DC current.

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What about the giant capacitors that are used in substations and along power lines for voltage support?

You are right Doug. The fact is that in this case we are not speaking about normal capacitors but supercapacitors. Since according to the article mentioned by the OP such supercapacitors can be charged in 16 seconds I suspect that they are not charged as it is done in normal capacitors with DC current.

Raffy.Roma said:

You are right Doug. The fact is that in this case we are not speaking about normal capacitors but supercapacitors. Since according to the article mentioned by the OP such supercapacitors can be charged in 16 seconds I suspect that they are not charged as it is done in normal capacitors with DC current.

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The paper never ever said anything about an 85kWh capacitor (be it super or ultra or whatever you want to call it) being charged in 16 seconds. In their experiment they were able to charge it in just 16 seconds, but I'm sure these were tiny. Impressive none the less with such high energy density, but no where near real world application yet.

@Johan

Ok I am waiting for more details on supercapacitors. Because of the high energy density my bet is that supercapacitors will not be charged as normal capacitors.

I think supercapacitors need a little more time for the charge to be distributed around, that is why 16s is a noteworthy value. "Normal" capacitors charge and discharge in microseconds.

What about capacitors for flux?

LazMan said:

What about capacitors for flux?

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What are capacitors for flux?

Electric700 said:

More here:
Charged EVs | Graphene supercapacitor packs basketball court-size surface area into one gram

Click to expand...

Going to the arxiv.org research paper, I found this info:
http://arxiv.org/ftp/arxiv/papers/1311/1311.1548.pdf

The discharge capacitance and energy density values, 195 Fg-1 and 83.4 Whkg-1, are achieved at a current density of 2.5 Ag-1. The time required to discharge 64.18 Whkg-1 at 5 A/g is around 25 sec. At 7.5 Ag-1 current density, the cell can deliver a specific capacitance of about 137 Fg-1 and maintain 98 % of its initial value after 10,000 cycles, suggesting that the stable performance of supercapacitors at high current rates is suitable for fast charging-discharging applications.

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(Caveat: I haven't read it all and don't understand it all.)

Since the usable current density in an electric car would be much lower (unless the Supercapacitor pack is very small), the usable energy density appears to increase to 83 Wh/kg. That's about a third of the energy density Elon was recently mentioning for LithiumIon (~ 250 Wh/kg). So very high for a Supercapacitor. And perhaps good enough to be used to augment a Lithium-Ion battery for the acceleration/regeneration cycles.

Have to say I'm very suspicious of this claim: (unless "near future" is meant to include something like 5-10 years).

The supercapacitor energy storage devices with high specific capacitance and short charging time demonstrated here can be scaled up for manufacturing in the near future for electric vehicle applications.

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The text mentions that material cost should be low, but that doesn't necessarily mean that contemporary production cost for this very new technology would also be low. And I'd guess that in order to make sense, the Supercapacitor pack would need to have a certain size, which places a limit on the cost.

Yeah, so in my brief experimenting as a teenager, capacitors dump their charge instantly. Is it possible to meter out small amounts of current over time, as desired for a car application? How long would it hold that charge, without leaking?

What would elements would it take to control it?