Captret - Capacitor and Electret

[NickZ]

   All:
   I'm still trying to figure which caps work best, also.  The capacitor  that seams to show the strongest effect (for me) is a 82 uf 400 volt. If I had more of them, like 4 to 6 or them, I'm sure the leds would light much brighter. In anycase the brightness is totally dependent on the voltage. Providing less than about 15 volts will not give any usable or   adequate brightness from the leds. If I don't connect any leds bulbs to the Captret, the caps will sustain their charge, or even raise in voltage by 1/2 a volt or so, but not much higher than that. Even after days. I've never seen any more than about one volt higher than whatever it started with.  But, an interesting effect is to add more voltage while the device is operating, (wall outlet etz...) then after a short while (a minute) disconnect the extra voltage, and the Captret's leds will retain their brighter appereance for a while, somewhat like the Joule Ringer effect, but for a longer duration than expected.
  I have some 9 volt batteries that still have almost all their original charge after 9 days use as part one of my Captrets (8-9 v).  But, I have not had much luck with connecting one battery to the next one by plugging them into each other. So, I think that it may not be the best way to add more batteries or voltage to the device, as the batteries discharge unevenly,  one compared to the other battery plugged into it, for some reason.  Anyways, I'm still at it...
 

[exnihiloest]

Just a remark. We can't speak about "self-charging" if the voltage doesn't not exceed at least 2v, because in this case we are below the redox potentials which can be provided by ordinary chemical reactions at the electrode/electrolyte interface.

I tested some "modern" capacitors yesterday, there was less than 1v. Thus it is not conclusive, conventional phenomena can be involved.
I have also old capacitors dating the 60's or 70's, in the range 400v, 200 µF. It will be my next step this evening.

[hartiberlin]

Hi All,
please see this edited picture.

In my experiments I did not need the connection with the
red cross, then the captret just works as a normal series resistor
for the LED.
As the alucase of the cap is internally only connected via the electrolyte
to the cathode foil, I wonder, if the cap is not chemically
decomposing this way, if you run a DC current from the ALucase to the negative
cathode foil or at least if it will change the capacitance of the capacitor over time ?

We really have to analyse what is going on internally chemically.

Regards, Stefan.

[hartiberlin]

Well, to explain it further,
what I painted as internal resistance is of course the resistance
of the alucase via the electrolyte to the negative pole
of the capacitor.
So it is mainly the electrolyte that is this internal resistance.

If you look closely you see, that the negative pole of the
capacitor gets a positive potential via the LED from the battery.

So if you measure across the negative pole of the cap to its alucase,
it has a positive voltage.

Now does this positive voltage decompose the electrolyte
or the aluminiumoxid layer inside the cap ?

This is the big question....

Regards, Stefan.

[NickZ]

   All:
   I have noticed that several (but not all) of the capacitors that I have used in the Captrets are bulging and leaking after using them in the captret system.  I think that the higher the voltage used (20 volts), the more damage is done to the caps.  Reminds me of the regular AA batteries and how they leak if charged.  The caps are not made to be used for this purpose, but there may be some types of caps that can possibly hold up better than others. All of the caps I used were of higher voltage ratings than the voltage applied to them, but they were also used caps from old pc power supplies, and such.  Maybe using the right caps for this purpose would work much better.  There is an effect going on, but I don't think that it very usable on a long term basis. The caps bulge and leak, and the Captret still is discharging the battery if more than one led is used.  If no led is used the caps maintain there voltage without dropping, but hardly raising in charge, either.  The led is the thief of the joules. With just one led bulb the system can maintain its charge without dropping by more than a volt, or so. 
  The only thing that I've learned from this is that most of my transistors, caps and almost all my leds have burned out or fried.

   I don't understand the Red X in your diagram, Harti.  Does that mean to not use the positive rail of the cap?  Thanks for the helping hand, as we are working hard at this, but maybe getting nowhere.
  It would be great to figure out how to make this work without any damage to the components, and still have some usable light.
                                                                                           NZ