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How long until supercapacitors overtake batteries in EVs?

10 years? 15? Any insights please?

Graphene supercapacitors could have to 64 Wh/kg, at which point they are a viable solution if not close to.
Graphene Supercapacitors Ready for Electric Vehicle Energy Storage, Say Korean Engineers | MIT Technology Review

Also supercapacitors in cars is not something new at the moment, such as the Toyota TS040 hybrid and Chinese electrical buses.

And slightly of topic, if 5 - 10 years is the relevant timeframe does this start to effect the economics of the gigafactory?

Thanks,
Daniel
 

rabar10

Model 3 >> Focus Electric
Moderator
Dec 3, 2010
1,455
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Indianapolis, IN
Secondary headline from that article:
Conventional batteries take so long to charge that they cannot efficiently store braking energy. Graphene supercapacitors store almost as much but charge in just 16 seconds.
I challenge the notion that efficiently storing regenerative braking energy is the limiting factor in "conventional battery" EVs.

Supercapacitors could be used in tandem with higher-spefic-energy and lower-specific-power battery chemistries, but that adds complexity and power conversion losses, as opposed to developing/using a single battery chemistry that provides a sufficient balance of both. Also, supercaps are chasing a moving target as battery chemistries continue to advance.
 

ItsNotAboutTheMoney

Well-Known Member
Jul 12, 2012
11,995
10,309
Maine
Secondary headline from that article:

I challenge the notion that efficiently storing regenerative braking energy is the limiting factor in "conventional battery" EVs.

Supercapacitors could be used in tandem with higher-spefic-energy and lower-specific-power battery chemistries, but that adds complexity and power conversion losses, as opposed to developing/using a single battery chemistry that provides a sufficient balance of both. Also, supercaps are chasing a moving target as battery chemistries continue to advance.

Even if a supercapacitor can handle super high C rates, you have to get the charge to them. Power electronics (which are falling in cost along with batteries) are quickly becoming a key cost barrier. JB Straubel, in response to the last question Q&A at the end of his storage keynote talked about them (power electronics that can stand automotive use) falling to around $100/kW in the near future. Would anyone but a racing team really put in thousands of dollars of electronics just for high regen?
 
As I understand it, supercapacitors, like lithium-air batteries, are not suitable for moderate-to-heavy loads over extended periods. Lithium-ion batteries are much more suitable for that. Tesla actually has a patent for a system that uses a lithium-air battery in combination with a lithium-ion battery pack. The concept is that the lithium-air battery, after being flash-charged, is used to trickle-charge the lithium-ion pack while driving.
 

ggr

Expert in Dunning-Kruger Effect!
Moderator
Mar 24, 2011
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30,086
San Diego, CA
As I understand it, supercapacitors, like lithium-air batteries, are not suitable for moderate-to-heavy loads over extended periods. Lithium-ion batteries are much more suitable for that. Tesla actually has a patent for a system that uses a lithium-air battery in combination with a lithium-ion battery pack. The concept is that the lithium-air battery, after being flash-charged, is used to trickle-charge the lithium-ion pack while driving.

Regeneration rate in the Teslas is limited by software, to ensure that the car remains safe and controllable. Regen acts only on the rear wheels, so unless you like, and have practiced, handbrake turns, you really don't want it much stronger than it is. The battery is perfectly capable of taking more.
 
Regeneration rate in the Teslas is limited by software, to ensure that the car remains safe and controllable. Regen acts only on the rear wheels, so unless you like, and have practiced, handbrake turns, you really don't want it much stronger than it is. The battery is perfectly capable of taking more.

I think your reply might have been intended for the previous post, not mine.
 
Secondary headline from that article:

I challenge the notion that efficiently storing regenerative braking energy is the limiting factor in "conventional battery" EVs.

Supercapacitors could be used in tandem with higher-spefic-energy and lower-specific-power battery chemistries, but that adds complexity and power conversion losses, as opposed to developing/using a single battery chemistry that provides a sufficient balance of both. Also, supercaps are chasing a moving target as battery chemistries continue to advance.

Totally agree.
You can panic stop any car from any speed with the brakes much faster than that car can accelerate. It is possible that this can generate more energy than batteries/charging system can absorb in that time.
However that is not a scenario that matters to anyone outside of a racetrack.
As long as the batteries can absorb the energy from descending a mountain pass, or rolling to the typical traffic stop, then no significant energy is wasted.
 
if you look at the demise of LiFePO4 vs the success of LiCoO2 based cathodes you could say that energy density is a very important (if not the most important) roadblock to be bypassed in the trek towards cheap EVs. LiFePO4 has around 2/3 the capacity of LiCoO2, similar voltage but is able to operate at rates 10 times higher than LiCoO2. As a result, if the rate of charge is what limits the development of EVs right now, then LiFePO4 should have won the market. It is however clear that it is energy density which drives the EV market. That additional 1/3 in capacity keeps the LiCoO2 as the de facto commercial cathode for rechargeable Li-ion batteries since its first application by Sony in the early 90s.

Based on these current events, i dont see any trend suggesting capacitors (tiny energy density with very fast rates) could overcome batteries (moderate energy densities with moderate rates).
 
Graphene supercapacitors could have to 64 Wh/kg, at which point they are a viable solution if not close to.

How is 64 Wh/kg anywhere close to a viable solution? To put things into perspective, 85kWh worth of these supercaps would weigh 1328kg (2928lb) alone. That's almost as much as my entire 05 Subaru Legacy weighs. And that's not even taking into account how much volume this monster power pack would take (I can't imagine carbon supercaps have particular great Wh/L compaired to li-ion batteries either).

Maybe sporty hybrids with formula-one style KERS might be able to use them but for any sort of plug in vehicle, they're practically useless.
 
Last edited:

WarpedOne

Supreme Premier
Supporting Member
Aug 17, 2006
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8,303
Slovenia, Europe
SuperCaps at 60Wh/kg could be usefull in 'non-plug-in' hybrids that use batteries with only a few kWh. Because of very high cycling those few kWh batteries must have much higher max capacity but newer use all of it - only its middle range to prolong lifetime.
Because of low capacity, they have low power.

A hybird car with say 2kWh of supercaps could use all o those 2kWh energy from 50kg of supercaps, delivering many tens of kW for some seconds. 100kW for 10s is only cca 300Wh of energy used. No battery of few kWh can output a 100kW (50C!) of power and survive to tell the tell. 50C for supercap is nothing.

In a pure EVe, there is no place for SuperCaps. You want stronger regen? Use a bigger battery. More power? Use a bigger battery.
 

WarpedOne

Supreme Premier
Supporting Member
Aug 17, 2006
4,472
8,303
Slovenia, Europe
Just for perspective ...
Skeleton Technologies
announced ultracaps with highest energy density that I could find - over 10Wh/kg.

Their SkelCap SCHE3500 has 3500F at 2,85V, weighs 0,39kg and "consumes" 0,281 L of space.

100 of those would weigh ~40kg, consume ~30L of space and store a bit under 400 Wh of energy.
Connected in series they would be at 285V max with max current of ~3000A. That is over 800 kW of burst power for 1s.

400Wh may sound small but it is not. A 1500kg (3000pound) car going 100km/h (60mph) has ~170Wh of kinetic energy.
Imagine what those 170Wh do to a car that smashes into a concrete wall.

Such 40kg UltraCap pack could be used for "miliHybrids" - ICE cars with electro-assist to reduce emissions during acceleration, enable regen braking. Current hybrids have ~5times bigger batteries but much of that capacity is never used due to "battery conservaition".

Their biggest advantage over batteries is life time: 1M cycles and 10 years for 70%NOM capacity.
And operating temperature between -40C and 60C with no heating or cooling necessary.

DataSheet

Unfortunately, no word on their pricing...
A quote from 2010:
A 3000 Farad ultracapacitor has an average selling price of $40, and Maxwell has sold millions of units over the years
100 x 40 = 4000 USD for ultracaps only. Yikes!
 
It won't happen until they repeal the laws of physics.

A capacitor makes a good filtering device because it can store charge on the plates, but it is not a good energy storage device. It's energy is .5 * C * V^2, and the voltage sags quickly as the charge is depleted to supply current. This voltage sag makes it impossible to power an EV running an electric motor.

When empty they look like a short-circuit to DC current, and look like an open-circuit when full. To AC they pass current like a variable resistance whose value varies depending upon frequency.
 
With a future generation of supercapacitors made available within the next 5-10 years, it's hoped that it will be possible to replace lithium-ion batteries. Scientists and engineers are working right now on the following supercapacitor goals:

-Maintaining the current lifespan of supercapacitors at greater than 25 years
-Storage capabilities per unit volume near or exceeding lithium-ion batteries
-Faster charging characteristics when compared with lithium-ion batteries

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

It won't happen until they repeal the laws of physics.

A capacitor makes a good filtering device because it can store charge on the plates, but it is not a good energy storage device. It's energy is .5 * C * V^2, and the voltage sags quickly as the charge is depleted to supply current. This voltage sag makes it impossible to power an EV running an electric motor.

When empty they look like a short-circuit to DC current, and look like an open-circuit when full. To AC they pass current like a variable resistance whose value varies depending upon frequency.
 

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