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.
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.
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 ...