# Ultra Caps .. Super Caps

Discussion in 'General Electronics Discussion' started by AprilSteel, Mar 30, 2017.

1. ### AprilSteel

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9
Feb 2, 2017
I started a thread "Capacitor Protection Boards- How do they work?" at this link
So I have got an idea of whats going on with them now . I'm using them to safely charge up a bank of 6 Ultra caps of 2.7 Volts and 300 Farads each Giving about 16.0 Volts when fully charged .

I have found that these caps hold a charge for quite different and varying amounts of time . It seems also to depend where in the string of capacitors each sits as to what voltage it will hold and for how long .

They are connected in series and the first being negative connection out and the last being the positive connection out . The protection boards are wired one end of the board to the negative ,the other to Positive and then a wire to the joining link between each capacitor .

So I am interested to know if there is a reason for the outside ends of the capacitor series chain to lose voltage quickly and for the insides of the chain (C4 & C3 below)to hold the most voltage for the longest time . I can charge the whole bank up safely at about 1 amp through the protection boards , get it to 16.0 and all led lights are on ,disconnect the protection board and then within a day the end caps can be under 1 volt and the middle still at 2.5 Volts.

I can find no references to this in the material I have found on capacitor chains. I have attached some material on the boards and the circuit.

Last edited: Mar 30, 2017
2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Let's assume that the 200F cap discharges from 2.7V to 1V in 24 hours and that the leakage current is constant.

I = c dv/dt
= 200 x 1.7 / 86440
= Approx 4mA

I presume you've swapped the caps around to check is not the capacitors.

If not, I'd remove the carrots and read the resistance with a multimeter. I'd the resistance around 400 ohms? That's really low, maybe something is damaged.

3. ### kenny Boss

1
0
Mar 30, 2017
hey guys ...any body .... I need help on something ...

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
You need to ask a question. But not in someone else's thread

5. ### AprilSteel

111
9
Feb 2, 2017
Its 300F so 300 x 1.7/86440= .0059 0r 6mA.
I went to uni and studied physics and electrical engineering for 2 years and never understood the dv/dt thing properly. But OK change of voltage over time.
I have not swapped them but have a second bank made up which demonstrates the same characteristics.
If I could get carrots out of them I would grow them and avoid the soil . Arn't these smart phones really smart.
I have not checked the resistance . Never have on a cap but I will try that this morning .

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
No, check the resistance of the board where the cap connects, not the cap!

Also, try charging up the caps and disconnecting them. See if any discharge faster than the others over a period of 24 hours or so.

7. ### AprilSteel

111
9
Feb 2, 2017
Ok Ill check the resistance of the board.
I thought that was wierd but was willing to try. I was studying this https://en.wikipedia.org/wiki/Equivalent_series_resistance
Some caps discharging faster than the others is exactly what i have asked about and exactly what is happening on both of my banks . Thats the point of the thread . Would there be a reason for this when caps are connected in series

Last edited: Mar 30, 2017
8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
That's what we're trying to find out:

1) Do some caps discharge faster than others when NOT connected to the board?
2) Is there some unexplained low resistance across some of the capacitor connections?

For each of the places where the capacitors connect, check the resistance with the probes both ways, first with the red probe where the +ve of the cap goes, then with the black probe there. Id the caps are not numbered, number then 1 to 6 from the one closest to negative to the one closest to +ve of the string.

Make a nice neat table of results so we don't get anything confused.

There is no good reason why some caps should discharge faster than others, however remember that capacitors are not generally viewed as long term power storage.

9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Oh, and post some pictures of your actual board

10. ### AprilSteel

111
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Feb 2, 2017
OK steve thanks . Pics done . I reminded myself that they are 500F caps too not 300

11. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
How's the "beautiful one day, perfect the next" weather around the great barrier reef at the moment?

12. ### AprilSteel

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Feb 2, 2017
Cyclone went down south of me through Airley Beach Proserpine and I did not feel a breath of wind nor a drop of rain . Incredible really for the size of it . They are suffering down south though. The reef is pristine blue today

13. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Wow, you must be pretty far north. I have friends in Mission Beach who got plenty of rain. (I think they got theirs days before it crossed the coast though)

I've been through a cyclone close to that size. It's not an awful lot of fun (and I was in a house built like a concrete bunker)

14. ### AprilSteel

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Feb 2, 2017
Steve I am about 3 hours north by road of Mission and a short helicopter ride east. Lizard Island mostly but spend time on the Atherton Tablelands and Cooktown -Just so you know.

My friend is working on this project
https://www.sciencedaily.com/releases/2017/03/170331120317.htm
I am just trying to establish a basic knowledge of Supercaps to hold a conversation without being left out.

15. ### davennModerator

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Sep 5, 2009
that's a nice area

16. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Capacitors and batteries both have some of their critical properties determined by surface area. Fractal surfaces will benefit both.

Both battery and capacitor technologies (I think) will be unimaginably different if some of this research can find its way to market.