# Which type of capacitor charges the fastest?

#### Sandul Henry

Joined Dec 2, 2018
24
Say one has a electrolytic, film, tantalum, and ceramic capacitor, each at 10 µf. When plugged into 1.5v source, which one will charge the fastest and why? This is for a hypothesis, so don't drag in ERS's, please.

#### crutschow

Joined Mar 14, 2008
32,026
The main difference between them as far as rate of charging is ESR, so if you "don't drag in ESR's", they will essentially charge at the same rate.

#### ericgibbs

Joined Jan 29, 2010
17,410
hi SH,
A simple dual LTS plot of the 3 types, with their ESR as LTS specified and their ESR=0
What is the hypothesis supposed to demonstrate.?
E

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Joined Mar 10, 2018
4,057
Parasitics control this, leakage, soakage (affects measurement), inductance, ESR, V vs C effective,
current state of water level in the Aswan damn.........

Regards, Dana.

#### Sandul Henry

Joined Dec 2, 2018
24
hi SH,
A simple dual LTS plot of the 3 types, with their ESR as LTS specified and their ESR=0
What is the hypothesis supposed to demonstrate.?
E
Well, my question is "What type of capacitor charges the fastest?" And because it is a Sci Fair experiment, I need a hypothesis formulated before I start testing.

#### ebp

Joined Feb 8, 2018
2,332
What would your null hypothesis be?

What information have you found that might falsify your null hypothesis?

#### Sandul Henry

Joined Dec 2, 2018
24
What would your null hypothesis be?

What information have you found that might falsify your null hypothesis?
I don't have a null hypothesis, because there is no claim. Therefore, the null hypothesis would be whatever capacitor people agree will charge the fastest. An alternative hypothesis would be if any other capacitor turns out to charge the fastest.

#### ebp

Joined Feb 8, 2018
2,332
What would the general null hypothesis be in anything at all like what you want to investigate? What would it be for say something like how the color of tires on a car influence the maximum speed of the car?

#### Sandul Henry

Joined Dec 2, 2018
24
What would the general null hypothesis be in anything at all like what you want to investigate? What would it be for say something like how the color of tires on a car influence the maximum speed of the car?
Well, I suppose the null hypothesis will be an if/then. It would appear like so (NOTE: this is an example, not the actual hypothesis) "If these types of capacitors are plugged into a 1.5v source, then the tantalum capacitor would reach maximum charge in the shortest amount of time.)

#### wayneh

Joined Sep 9, 2010
17,261
Well, I suppose the null hypothesis will be an if/then. It would appear like so (NOTE: this is an example, not the actual hypothesis) "If these types of capacitors are plugged into a 1.5v source, then the tantalum capacitor would reach maximum charge in the shortest amount of time.)
I would say the general null hypothesis is that they're all the same. You need data to prove otherwise and reject the null hypothesis. If you collect enough such data, you'll find that there are differences that are statistically unlikely to result from random error in the measurements. Additional data might support an additional hypothesis, that ESR is an important factor correlated to charging time.

#### WBahn

Joined Mar 31, 2012
28,465
I don't have a null hypothesis, because there is no claim. Therefore, the null hypothesis would be whatever capacitor people agree will charge the fastest. An alternative hypothesis would be if any other capacitor turns out to charge the fastest.
Are you trying to explore capacitors, or people's thoughts regarding capacitors? I would imagine you could do a decent Science Fair project on either topic, but if you are trying to explore capacitors, then what people do or don't agree to has zero relevance unless you think (or are trying to test the claim) that capacitors are aware of what people believe about them.

#### Sandul Henry

Joined Dec 2, 2018
24
I would say the general null hypothesis is that they're all the same. You need data to prove otherwise and reject the null hypothesis. If you collect enough such data, you'll find that there are differences that are statistically unlikely to result from random error in the measurements. Additional data might support an additional hypothesis, that ESR is an important factor correlated to charging time.
I suppose your right, because that is technically a valid hypothesis. Therefore, do you think that my hypothesis should be (in a if/then/because format) : If these capacitors are plugged into a 1.5 volt power source, then the time it takes to charge the capacitors to the maximum voltage should be the same across all of them., because they all have the same capacitance (47 µf) and I do not exceed the voltage rating.

#### MrAl

Joined Jun 17, 2014
10,054
Hello,

We can talk about this without *keeping* ESR in the equation, but we still must consider that in order to figure out the right answer, then later sort of cancel it out so it is no longer a part of the solution. This will happen because the answer would be in the form of voltage vs time which does not (any longer) include ESR.

Since we know for a FACT that the lower the ESR the faster a cap charges when subject to an ideal voltage source forcing function in the form of a unit step, we can look at all the cap types and find out which one has the lowest ESR possible. We can then claim that is the one that will charge the fastest, and that does not need to include ESR anymore it just needs to state the capacitor type.

So what you are looking for really is the type of cap that today has the lowest ESR possible, and that is your answer.

#### wayneh

Joined Sep 9, 2010
17,261
Are you planning on actually collecting data? I think it will be difficult to see the charging time with enough precision to tell one from another. You’d need a good oscilloscope and even then I’m not sure what you’ll see unless you add some resistance to slow things down. But then you’re not so much looking at the capacitor as the resistor.

Using a high frequency AC signal might be a better technique for showing differences.

#### Sandul Henry

Joined Dec 2, 2018
24
Hello,

We can talk about this without *keeping* ESR in the equation, but we still must consider that in order to figure out the right answer, then later sort of cancel it out so it is no longer a part of the solution. This will happen because the answer would be in the form of voltage vs time which does not (any longer) include ESR.

Since we know for a FACT that the lower the ESR the faster a cap charges when subject to an ideal voltage source forcing function in the form of a unit step, we can look at all the cap types and find out which one has the lowest ESR possible. We can then claim that is the one that will charge the fastest, and that does not need to include ESR anymore it just needs to state the capacitor type.

So what you are looking for really is the type of cap that today has the lowest ESR possible, and that is your answer.
So, just to clarify, looking for the the cap that could reach the max faster, is the same as looking for the one with the lowest ESR?

#### Sandul Henry

Joined Dec 2, 2018
24
Are you planning on actually collecting data? I think it will be difficult to see the charging time with enough precision to tell one from another. You’d need a good oscilloscope and even then I’m not sure what you’ll see unless you add some resistance to slow things down. But then you’re not so much looking at the capacitor as the resistor.

Using a high frequency AC signal might be a better technique for showing differences.
Yes, I am collecting data. The said data is the time it takes to charge the capacitor, from under 1.5v, to 1.5v (Of course, as caps cannot reach 100%, I just call it at 1.49v)

#### wayneh

Joined Sep 9, 2010
17,261
So, just to clarify, looking for the the cap that could reach the max faster, is the same as looking for the one with the lowest ESR?
Yes. If charge time doesn’t correlate very strongly with ESR, you’d have to question your instruments.

#### ebp

Joined Feb 8, 2018
2,332
Things to consider:

What are the equation for the charging time of a capacitor if there is resistance in the circuit?
If there is resistance in the circuit, what does a plot of the voltage on the capacitor versus time look like?
Does the shape of the curve suggest anything about what voltage you might use for your time measurement point in terms of how consistent you can be if you have to evaluate when the charging has reach some fraction of "completion?'
Where would there be resistance in the circuit? Will it be consistent from one test to another?
How would you quantify that resistance?
How long does it take a capacitor to charge to a voltage equal to the supply voltage if the supply is "ideal"- can deliver infinite current?
Is your voltage source reasonably like and ideal source? (Can you put together a test circuit and actually record how the voltage on the capacitor changes to try to assess this? e.g. with a digital oscilloscope?)
How will you determine the actual value of the capacitor being tested? Do you know about component "tolerance?"

And the big one: Why is this matter of interest? Is it purely "academic" or is there some practical importance?

A warning: solid tantalum capacitors do not "like" being charged very rapidly with high current. They have a tendency to fail short-circuit. Some types actually have built in fuses to prevent major problems if the cap fails short-circuit.

#### SLK001

Joined Nov 29, 2011
1,548
The ceramic capacitor will charge the fastest (lowest ESR!). And @crutschow is correct, if you throw out ESR considerations, they all will charge at the mostly the same rate (there is dielectric absorbsion that has to be considered also).

#### MrChips

Joined Oct 2, 2009
28,471
And how are you going to measure the charge time?

The charge time is approximately = 6 x R x C seconds.

Since R is practically zero, the charge time is almost 0 seconds.
Even if we make R = 0.1 Ω, charge time = 6 x 0.1 x 10μs = 6μs
Do you have equipment to measure 6μs?