[Karter2]

But the basics remain..
There is no known capacitor device that can give this capacity , in this size , or at this weight...let alone cost.
ALL the data and evidence still confirms that this is using LTO cells..
...just as those new "supercapacitor rechargeable" AA cells are also !
Its all on the AEVA forum

 

[weber]

The energy stored in a capacitor is not linear with voltage as it (sort of) is with batteries.

Energy = Capacitance * Voltage * Voltage / 2

So at double the voltage you have 4x as much energy. At 4x the voltage you have 16x as much energy.

It does actually make sense that the voltage skyrockets immediately under very little current flow, and that by the time you drain it even to half voltage, most of the energy is long gone.

This would only be relevant if the charge tests used constant power. They don't. Some are constant voltage (where the device's internal resistance limits the current), others are constant current. With constant current, voltage increases linearly with time for a capacitor.

But even if it was relevant: When you transpose the above equation to give the voltage as a function of the energy, you get: Voltage = sqrt(2 x Energy). Sure, that starts off steeper than it ends, but it is a very smooth and rounded sort of curve. The curves for this device have a very sharp knee in them at around 1.8 to 2.0 volts.

 

[MattsAwesomeStuff]

With constant current, voltage increases linearly with time for a capacitor.

I don't think that's true.

As you add energy into the capacitor, voltage increases as per the formula.

In any case, was just nitpicking a point Duncan made.

It's important when something is bullshit, that the reasons you debunk it aren't bullshit too. This thing is bullshit enough that it is plenty sufficient to debunk it using a dozen valid arguments, so it's important to make sure those are accurate. Duncan was on the right track but, off on one attribute.

I say this as someone who occasionally picks up bits of context in threads like this and finds out years later it was wrong, or years later come across threads like this where no one corrected it and then "learns" something untrue.

Evidence is clear they're LTOs, nothing to see here.

 

[Duncan]

Evidence is clear they're LTOs, nothing to see here.

You are probably right but I'm still struggling with why a company would try and sell something that was not what they say it was

A one off sale? - sure con men are everywhere

But a mass produced article where they would need to sell thousands just to cover the initial costs?

 

[weber]

I don't think that's true.

As you add energy into the capacitor, voltage increases as per the formula.

Yes. But constant current doesn't correspond to constant energy per time, it corresponds to constant charge per time. And, for a capacitor, voltage is charge divided by capacitance and energy is charge times voltage. So constant current means energy is going up as the square of time. And since voltage goes up as the square root of energy, voltage goes up linearly with time.

It's important when something is bullshit, that the reasons you debunk it aren't bullshit too.

Yes. Absolutely. So please, don't take my word for it. Look this up elsewhere, to understand where you're going wrong.

Evidence is clear they're LTOs, nothing to see here.

Agreed.

 

[MattsAwesomeStuff]

Hopefully not a hijack, not sure this thread has much more use in it, after its thorough debunking...

Yes. But constant current doesn't correspond to constant energy per time, it corresponds to constant charge per time. And, for a capacitor, voltage is charge divided by capacitance and energy is charge times voltage. So constant current means energy is going up as the square of time. And since voltage goes up as the square root of energy, voltage goes up linearly with time.

Hrm, I'm half-following you here. (I'm sure it's a fine explanation, but I have only a beginner's grasp of it). I get that energy and current are different, and that voltage starting low means energy going in starts lower, I'm just not sure the two cancel out entirely, one is squared, one seems linear to me.

But let me rephrase what you're claiming...

If I take a constant-current power supply, set it to some low current with a max voltage of whatever my capacitor is, and pick a capacitor that is large enough that it charging is watchable on a human-timescale...

Suppose I pick a 50v capacitor. And I measure and it takes, oh, 5 minutes to charge at whatever rate I picked. You're saying that at 1 minute it was at 10v, 2 minutes it was at 20v, 3 minutes it was at 30v, 4 minutes it was at 40v along the way?

I'll have to try that on some suitably-sized capacitor some time.

 

[weber]

Yes. That's exactly what I'm saying.

 

[brian_]

... So the 3.55kWh pack would actually be a 7 kWh pack that they were only using 3.55 kWh

But again, the distributor (the manufacturer is nowhere to be seen in this discussions) has repeatedly claimed that they are using all of the energy in the capacitors, not just partially discharging them.

 

[Karter2]

Arvio keep shooting themselves in the (reputation) foot over on the AEVA forum.
http://forums.aeva.asn.au/viewtopic.php?f=17&t=5486&start=200
Thankfully, weber is doing a great job of hosing down the BS. !

 

[MattsAwesomeStuff]

Thankfully, weber is doing a great job of hosing down the BS. !

Weber just slayin' their claims left and right.

'We're still waiting for you to explain why, when you remove the Kilowatt Labs sticker from your claimed USB-chargeable AA-sized "graphene supercapacitor", it says "LTO" and "battery"? And why the words "graphene" and "capacitor" are nowhere to be found?'

Merciless

 

[Duncan]

Just bumping this thread as they have started selling these here in NZ - the 3.55 kWh unit is about $4K so I don't think I'm going to buy one just to pull it apart

But any more news from Australia where they are a year ahead of us

 

[somecallmetim]

I've been curious about using a supercapacitor for energy storage for some time. I don't think the value proposition is to replace a battery for the same purpose, but perhaps in a similar location in the drive train, with a different function.


A supercapacitor charges and discharges very easily. Charge is stored as charge, rather than requiring chemical conversion to store energy and chemical conversion to release energy.

The contrast with a battery is that a battery must be large - not just to provide range, but also to allow maximum discharge current. How many "C"s are you willing to push your battery to in order to accelerate? If you keep the discharge per battery low, you need a larger capacity battery to source a given amount of current. That adds significant weight, and significant cost.


A supercap in a series hybrid would just function to provide power spikes at acceleration / deceleration, and keep the motor at peak efficiency.



I'm more interested in using supercapacitors as temporary energy storage, between a generator (or alternator with appropriate converter) and my electric traction motor. If I can supply the large current needed for acceleration and accept the large current generated with braking...that is the benefit.


This would need to be paired with an ICE or microturbine or free piston generator or... that would run near optimum efficiency to keep the supercapacitors at a programmed charge level.


I think that Ariel is working with Delta Motorsports on this sort of idea, and a couple of Chinese companies are as well (techrules comes to mind, but I think there is another that I can't recall at the moment).


Hypothetical (until I pull the switch )...


A tube frame car that weights 1700 lbs with low drag. Current versions use an ICE with a 160 HP engine and a 4-5 speed. The engine and transmission weigh about 205 kg (450 pounds). From my rough estimates, I could get a sufficient synchronous motor and gear reducer for 75 kg. Supercapacitor would weigh (much less than batteries) about 180 kg for 500V. I need a 20-30 kW generator. I could go wankel, microturbine, or freepiston...all of which are in the 15-20 kg range.



All told, on paper it looks to be about 75 kg heavier than the ICE version, with plenty of acceleration, optimum efficiency of the ICE, and no battery issues. Since an electric motor can be mounted transversely with gear reducer dumping power out on a parallel axis to the motor rotation, very low losses occur between motor and wheels.


Any thoughts on this sort of application?


Cheers...