Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by Nictron » Mon, 14 May 2018, 14:05

Thanks All for the information.

It does seem that they’ve developed some hybrid LTO/Capacitor solution that allows for longer lifetime and cycles. They have not provided me with any evidence to proove cycle life except for a reference from two of our big telecoms that have procured and tested them extensively and they are continuing with the rollout.

At the pricepoint this looks like better value than other quoted GEL and Lithion-Ion options I’ve recieved. 48x 100Ah GEL in 48V configuration is more expensive than 3x 3.55kWh Sirius modules.

Is it possible that they can extend the battery life by leveraging capacitor capabilities in a hybrid config? If I get 5000-10000 cycles at this price I’ll be happy with the value?

Much appreciyed,

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by jonescg » Mon, 14 May 2018, 14:20

If they cost twice as much as an LFP battery of equivalent capacity, you might as well buy a LFP battery of twice the size and get 4 x the cycle life (of an LFP battery half the size).

(Sorry about the editing - hit the wrong button...)
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by TCryptos » Mon, 14 May 2018, 14:38

They have not provided me with any evidence ..
All of the evidence provided to date indicates that the individual storage devices are LTO cells. We've seen zero evidence that any supercapacitors are present.

LTO cells seem a reasonable technology, but you should note carefully @weber's post above regarding cycle life and temperature.

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by weber » Mon, 14 May 2018, 15:28

Nictron wrote:
Mon, 14 May 2018, 14:05
It does seem that they’ve developed some hybrid LTO/Capacitor solution that allows for longer lifetime and cycles.
No. There's no evidence of that whatsoever, and considerable evidence that they are simply LTO batteries.
They have not provided me with any evidence to proove cycle life except for a reference from two of our big telecoms that have procured and tested them extensively and they are continuing with the rollout.
Exactly what form does that reference take? Can you post it?
...
Is it possible that they can extend the battery life by leveraging capacitor capabilities in a hybrid config?
No. The module is limited to a 2C (half hour) charge and discharge rate by its control electronics and its warranty. At those rates, parallel supercapacitors would have no effect whatsoever. And there simply isn't enough room in the case to fit any significant amount of supercapacitors in addition to the LTOs required to explain the storage capacity.
If I get 5000-10000 cycles at this price I’ll be happy with the value?
When I gave typical lifetimes for LTOs above, those were for manufacturers with some kind of honesty and decency, who were prepared to put their name on their devices. Who knows what floor-sweepings you'd be getting in these no-name LTOs that don't even admit they are LTOs.

And please consider the message you'd be sending to these lying bastards if you reward them by buying their product.
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by Nictron » Mon, 14 May 2018, 21:22

All good advise thanks. I’ll look into the LFP batteries suggested by @jonescg

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by Nictron » Mon, 14 May 2018, 23:24

jonescg wrote:
Mon, 14 May 2018, 14:20
If they cost twice as much as an LFP battery of equivalent capacity, you might as well buy a LFP battery of twice the size and get 4 x the cycle life (of an LFP battery half the size).

(Sorry about the editing - hit the wrong button...)
What should I be paying before taxes per kWh capacity for an LFP battery (LifePo4)?

Pricing here in SA seems in line with the Sirius units?

https://www.sustainable.co.za/solar-pow ... turer=1839

Thank you,

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by jonescg » Tue, 15 May 2018, 07:25

The going rate for LFP cells in Western Australia seems to be about AUD$580/kWh. Excluding BMS that is.
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by TCryptos » Wed, 16 May 2018, 12:32


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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by jonescg » Wed, 16 May 2018, 13:01

A rather diplomatically written article...
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by rhills » Wed, 16 May 2018, 13:10

Hi Chris,
jonescg wrote:
Wed, 16 May 2018, 13:01
A rather diplomatically written article...
That's one way of putting it I guess.

If you only read the first paragraph or two and you're easily influenced by these things, you'd rush out and buy one. However, if you read through to the end, and you'd followed this thread, you'd see a pattern of scepticism emerging...
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by Nictron » Thu, 17 May 2018, 22:44

Yup still sceptical. Early adoption is very risky in this regard.

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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by weber » Fri, 18 May 2018, 12:37

How to tell a Capacitor from a Battery

A capacitor is a cylindrical water tower. A battery is a dam up in the hills.


"What has he been smoking?" I hear you ask. Don't worry. I'll explain. :)

I see a lot of people saying that we won't be sure whether Kilowatt Labs' Sirius devices are supercapacitors or batteries until we have "independent tests". I'm all for more tests, but what more trustworthy data could you have, than data that shows the exact opposite of what the tester dearly hoped it would show?

I suspect that people who are still waiting for independent tests may be people who don't have the electrical training to be able to tell whether the data shows a capacitor or a battery, and that's perfectly understandable. If that's you, I suspect you might be just as happy if some authority that you trust, looked at the existing data and told you what it shows. Maybe, for whatever reason, you don't trust me, or the other engineers that have posted the same conclusion, or the dozens of other engineers reading this thread who have not disputed it. So I'm going to try to turn you into your own trusted authority on the matter. It's not really that hard to understand.

The water analogy

The time-tested way of understanding electricity is via the water analogy, where a wire is like a pipe and a quantity of electric charge is like a volume of water. Let's make one "coulomb" correspond to one cubic metre (1000 litres) of water. Like all analogies it has its limitations, but we won't be going anywhere near them in understanding the difference between capacitors and batteries. The analogy is nearly perfect for this purpose.

Electrical "current" is just what it sounds like—a rate of flow. One amp of electrical current is one coulomb of charge per second, so that's like one cubic metre of water per second going through a pipe. We could call a flow rate of one cubic metre per second a "water-amp".

Electrical voltage is like water pressure. Thanks to gravity, water pressure increases proportional to height. Specifically the height of the water surface above the ground level where we're measuring the pressure. So we could say that one volt is like one metre in height. However we're dealing with only 2.7 volts here, so I'm going to make one volt correspond to 10 metres in height, to make for more realistic water reservoirs.

The term "ground" has the same meaning in both domains, as the reference point for measurements of pressure.

A power supply is like a pump.

Your mission

In one of Paul Wilson's videos:
The electrical storage device is charged from empty using a constant current of 3 amps from a power supply. We see the voltage increasing with time. The test is stopped when the voltage reaches 2.7 volts. It takes about 20 minutes (1200 seconds).

We can translate that into water terms as:
The water reservoir is filled from empty using a constant flow rate of 3 cubic metres per second from a pump. We see the height of the water increasing with time. The test is stopped when it reaches 27 metres. It takes about 20 minutes (1200 seconds).

Imagine that your city council has paid for a water tower, because you've been told that water towers have magical properties compared to dams. But the company that built it won't let anyone see it. Your mission, should you choose to accept it, is to figure out whether the reservoir is a water tower or a raised dam, based only on a graph showing how the water height (as measured by a pressure gauge at the pump) varies with time.

How would you expect the water height to change with time if this was a cylindrical water tower standing on the ground beside the pump?

How would you expect the water height to change with time if this was a dam up in the hills, with a pipe running up to its lowest point?

Lets say its lowest point is 21 metres above the pump. Of course the area of the dam reservoir is much greater than the area of the base of the water-tower. Let's say that you have reason to suspect that the sides of the dam reservoir are vertical from 27 metres height down to 25 metres height and then they slope inward to the pipe opening at 21 metres.

capacitor battery water analogy.png
capacitor battery water analogy.png (2.82 KiB) Viewed 142 times

What would the graph of water-height versus time look like in each case, given a constant flow-rate and assuming they both have the same volume and both fill to 27 metres in 20 minutes?

A capacitor is a cocktail glass. A battery is a champagne coupe.



To be continued ...
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Re: Arvio 3.5kWh drop-in-battery-replacement supercapacitor on sale

Post by weber » Today, 12:15

I assume you've figured out that, given a constant flow rate from the pump, the height of the water in the tower will increase at a constant rate. So the graph will be a straight line, like this.

Water tower.png
Water tower.png (5.59 KiB) Viewed 69 times

The rate at which the water level rises (and so the steepness of the line on the graph) depends on the flow rate and the horizontal area of the tower. A skinny tower would fill sooner and so would have a steeper line on the graph.

The raised dam is a little more complicated. But we can think of the pipe as being a very skinny tower. The pipe will fill very quickly and so there will be a very steep line on the graph going up to 21 metres. Above 25 metres, the reservoir has a constant area too, so that will be a straight line, but a very gently sloping one, due to the large area. And in between these two straight sections, the graph will gradually go from steep to gentle. It will have a "knee", like this:

Raised dam.png
Raised dam.png (6.37 KiB) Viewed 69 times

So you can see it's like chalk and cheese.

But why should you believe me when I say, in this voltage-equals-water-height analogy, that a capacitor is like a water tower and a battery is like a dam in the hills? I encourage you to do your own google searches, looking for authoritative sources. But to save you the trouble, here's confirmation for the capacitor analogy, from no less than the Department of Electrical Engineering at the University of Pennsylvania. It also shows the straight-line graph.

Finding confirmation for the battery analogy is more difficult. Most uses of the water analogy don't treat batteries in any detail and simply say they are like a pump. If that was the case, they would never run out of charge! But you can readily find that the voltage versus time curve for batteries under constant-current charge look very much like the raised-dam graph above, and nothing like the water-tower/capacitor graph.

However, I'm not only claiming that the Sirius devices are batteries. I'm claiming they are a very specific type of battery—a lithium titanate battery. So let's look at some voltage curves for those. These curves come from an EETimes magazine article.

Image

Now let's look at the graph from Paul Wilson's constant-current charge test of a Sirius device. Note that the legend below tells us the blue curve is the voltage curve. We're interested in the constant-current part, which lasts until 1170 seconds. After that the current was turned down. You can right-click and chose "View image" to enlarge it. Or you can see it in the original video.



I rest my case. Any questions?
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