For Woopy: Explanation for why you lose 1/2 energy in a capacitor

[DreamThinkBuild]

Hi All,

I've seen this self charging that IB is referring to in ultracaps. Take two 3000F ultracaps and short each one individually down to about 5mv each(10mv total). Place in series and leave them for an hour and re-measure, it usually ends up with a +50mv gain or around 60mv total(~30mv each cap). Did the same experiment with six 3000F caps in series short until 1.6mv each cap, place in series at around 10mv leave an hour and the voltage is up around 300mv or a gain of around +48 to +50mv per cap. If you look at the datasheet for the caps it has a ESR of ".29milliohms" which might factor into this self charging.

Link to datasheet
http://www.maxwell.com/products/ultracapacitors/docs/datasheet_k2_series_1015370.pdf

I'm wondering how far you can take this self charge effect before it breaks down. Is it better to stack x amount of capacitors in series to reduce the capacitance, increase the charge rate but also increase the ESR which will cause it to have diminishing returns. Or would it better to put them in parallel which will decrease the ESR but at the expense of increasing the capacitance, slowing the charge rate. Hmmm... something to test.

[TinselKoala]

Charge in series, discharge in parallel.

[Magluvin]

Charge in series, discharge in parallel.

Hey TK

Ive heard this before. A few times actually.

Here is something I found interesting.

The pic below shows a circuit that has a source, 5v and when you close the switch to the left, hold till the cap is at 5v then release.

Now, to the right, we have 2 options. Insert the wire or the cap into the empty space.

With the wire, when we close the switch to the right, the caps end up at 2.5v each. ;]

But, now here is the strange part.

With the 3rd cap in place, we charge the first cap from the source to 5v, then discharge that into the 2 caps in series. We end up with 3.3v in the first cap and 1.67 in each of the series caps to the right.  Got it? ;]  Now for the trick...

We remove the 3rd cap from the circuit(still holds 1.67v) and insert the wire once again.
The cap on the left has 3.3v and the one to the right has 1.67v.  When we hit the discharge switch once again, we end up with 2.5v in each. 

And we are left with the 3rd cap with 1.67v.

Now how did we end up with 2.5v in each, just like when we didnt have the 3rd cap in the first example?

Mind boggling.      So why did we not lose as much in the second example as we did in the first, considering we still have a charge in the 3rd cap when all is said and done? ;]

Does this have something to do with your post that I just quoted? ;]

Mags

[Magluvin]

Actually, I would like MH to answer why this occurs first, even though Im itching to hear from TK on this.

But I want to see if MH's reasoning adds up here, considering its his thread. 

Mags

[MileHigh]

Magluvin:

Ever since I told you that your one-magnet no-bearing spinner was never going to work and your friend's clip was a fake you have gone ape-shit on me.  You have looked for opportunities to give me a hard time and you get argumentative to the point where most of what you say makes no sense and it's intentionally said just to add fuel to the fire.

The question that you posed to me that Poynt answered was a rigged question you intentionally made up to be as difficult as possible to start the same ridiculousness all over again.  You had no interest in getting the answer to that question, it was just an attempt to engage me in a fight.

So before I even discuss this, the question for you is this:

Is this over and are you going to stop this behaviour from now on or are you going to continue looking for opportunities to have "big fights" and throw insults at me and wig out?

So what's it going to be from this point onwards?

MileHigh