cap dump schematic questions

[Cmor]

Hi Gary,

Do you recall - once the correction was made to the sch. - if the 555 version ever performed well for other experimenters?

I'm getting ahead of myself, but just as you did, I want to build another SG, as the one I’ve made doesn’t have matched transistors and resistors, and I didn’t true the bike wheel with a spoke wrench - all of which will limit what it can do. When I get that one made I'll also switch to a comparator.

Thanks for the advice to use enough FET’s to handle the total capacitance I’ll be dumping. I get a rough idea of the number of FET's to add just reading what you did, but how do you calculate how many FET’s to use in relation to the capacitance?

I’d prefer to just run the SG and charge batteries directly from it (assuming that’s what generator mode means) but I want to start a business restoring dead vehicle batteries so I'll need to condition them with a cap dump.

On a bit of a tangent, I saw a post once saying that if one connected multiple batteries on the output side (apparently in series) that those after the first battery would be conditioned by it and thus would work as run batteries/batteries that would accept hot current later. Is that correct?

[Cmor]

Forgot to add, thanks for the photos!

[Gary Hammond]

Hi Cmor,

Hi Gary,
Do you recall - once the correction was made to the sch. - if the 555 version ever performed well for other experimenters?

Sorry, I don't recall. A search of old posts might answer that, or maybe someone else remembers.

how do you calculate how many FET’s to use in relation to the capacitance?

I just go by what John Bedini did. He used 4 "matched" FETs to dump 60,000 uf of 80 volt capacitors. So that would be one FET for each 15,000 uf. Each dump is well over 100 amps at that capacitance level. If I hold a magnet next to the leads from the cap dump to the charge battery on mine, each discharge pulse will strongly pull the magnet in my hand!

On a bit of a tangent, I saw a post once saying that if one connected multiple batteries on the output side (apparently in series) that those after the first battery would be conditioned by it and thus would work as run batteries/batteries that would accept hot current later. Is that correct?

Sorry, I've never heard that one and never tried it myself.

[Cmor]

Number of FET's

Hi Gary,

I just go by what John Bedini did. He used 4 "matched" FETs to dump 60,000 uf of 80 volt capacitors. So that would be one FET for each 15,000 uf.

Since I'll have (4) 18,000 uF caps, it seems like I should put in 4-5 (unmatched - my only option for now) FET's. Do you know if there's an advantage/disadvantage to having 5 instead of 4?

[Gary Hammond]

Hi Cmor,

The idea is to divide the discharge current up as evenly as possible (hence matched) and stay well within the current and voltage ratings of the FETs. The discharge is pretty rapid, so whichever FETs trigger first will carry the bulk of the current. Four might work and five might be better. I placed mine in European style terminal strips so I can replace them easily in case some of them blow.

[Cmor]

Thanks Gary. That's what I needed to know. I'll go with 5.
Given that they won't be matched there will be one that triggers first and conducts the bulk of the current. I imagine it will thus be more likely to burn out. At least now I'll know why.

You mean you attach them to one of these?

If so, do you attach them with the screws rather than solder?

[John_Koorn]

I just go by what John Bedini did. He used 4 "matched" FETs to dump 60,000 uf of 80 volt capacitors. So that would be one FET for each 15,000 uf. Each dump is well over 100 amps at that capacitance level. If I hold a magnet next to the leads from the cap dump to the charge battery on mine, each discharge pulse will strongly pull the magnet in my hand!

Slight correction - JB used 5 matched FETs in the Bedini Large Comparator... so about 12,000uF per FET



Picture taken from http://www.teslagenx.com/research/tx...egory=research

John K.

[Gary Hammond]

Hi Cmor,

Thanks Gary. That's what I needed to know. I'll go with 5.
Given that they won't be matched there will be one that triggers first and conducts the bulk of the current. I imagine it will thus be more likely to burn out. At least now I'll know why.

You mean you attach them to one of these?
[ATTACH=CONFIG]7087[/ATTACH]
If so, do you attach them with the screws rather than solder?

Maybe you'd better go with six FETs. (72000/12000 = 6) Sorry about my miscounting. My bad. I didn't look at the picture again before posting , and was just speaking from faulty memory.

Yes, those are the kind of terminal strips I used on my last cap dump with the comparator. And yes, I attached the FETs with screws so they would be easy to replace.

The FETs were soldered into my first (555 based) cap dump as you can see in the photo album I linked to earlier. Replacing them was not easy!

[Cmor]

Hi John,

I'm not ready to build my "next" cap dump, since I haven't even built the first one, but...planning ahead for when I do, does TeslagenX sell matched Mosfet's in addition to the matched BJT's?

[Cmor]

Hi Gary,

That it a great tip. I'll do that too. As for specifics, to get good contact, did you wrap the Mosfet legs around the screws before screwing them in?

[Faraday88]

Hi John,

I'm not ready to build my "next" cap dump, since I haven't even built the first one, but...planning ahead for when I do, does TeslagenX sell matched Mosfet's in addition to the matched BJT's?

.... and how is it matched? in the case of the Transistors it is the Hfe or 'Beta' of the transistor that is matched
what parameter of the MOSFET is needed to be matched?
Rgds,
Faraday88.

[Cmor]

Faraday88,

I don't know the answer to the details you're asking, but I think the "matching" is in terms of when they turn on, so they all turn on at once.

[Cmor]

Gary,

I mentioned a couple posts ago that I'd read something saying if several batteries were hooked up (I said in series, which was an error) that those after the first battery would be conditioned, just like in a cap dump. You hadn't heard about it, so I wanted to post the comment to see if you or anyone else has more feedback.
I don't remember where I copied it from (though maybe from an instructable), but here it is.

OK, why CAN we swap batteries that have been capacitor dump charged, but not diode direct charged? Because the capacitor has REGAUGED the energy and we can use the battery as primary immediately. Well, the batteries being charged in line AFTER the first secondary battery, in parallel on the back end, have the energy REGAUGED BY THE FIRST SECONDARY BATTERY that is hooked up to the output of the unit. It is just like getting the energy through a capacitor! Batteries are just really slow capacitors, after all. The only battery that CANNOT be swapped to primary is the first battery in line on the output side that is directly hooked to the radiant output.

[Michael Luton]

Cmor we are used to thinking in absolutes and rules, but I would like to run some ideas to you that are a bit more abstract. If I confuse the issue for you, just ignore me. Gary feel free to correct or override anything I write here.

1st a battery is not just a slow capacitor. A capacitor stores its charge in a dielectric field and a battery is a electrical charge – chemical reaction – storage – chemical reaction – electrical source device. They can sometimes be interchanged as a source but internally there are fundamental differences in the way they act.

The difference in the two charging methods are the sources. A coil stores energy in its magnetic field and on discharge has to make up the dielectric portion from the environment. A capacitor stores it's charge in a dielectric field and on discharge has to make up the magnetic portion from the environment. These two methods create a different quality in the electricity produced (which I do not fully understand) and effect the chemical phase of the battery charging slightly differently. This difference is why the batteries have problems with being switched.

The regauging that Beardon refers to means to me changing a reference point. In my opinion this is not a matter of regauging, but an issue of the energy being actually converted to something a slightly different form. Tesla said he could convert electrical energy at will, this may be a small part of what he was referring to.

All that being said I believe there is still too much not understood of all the effects that can be generated in a circuit. I think of Tesla's hairpin circuit and how if you add a capacitor you can sometimes add more loads after it. So if you you have some batteries you are willing to risk and the time to do a long term trial of your premise, I would say go ahead with the understanding that there is a lot more involved than your original statement indicated. Just let us know of your findings.

Michael

[Gary Hammond]

Hi Cmor,

Hi Gary,

That it a great tip. I'll do that too. As for specifics, to get good contact, did you wrap the Mosfet legs around the screws before screwing them in?

No, there is no way to do that. That's not how they are made.

The wire and/or mosfet leg just slips inside a sleeve. Then a recessed screw forces a lug down on top of it. The leads are securely held between the lug and the wall of the sleeve. The sleeve goes all the way through the plastic mounting strip and has a screw clamp on each end of each sleeve. The circuit wire goes in one end and the FET leg goes in the other end of a common sleeve.