Cap Dump Circuit

[BroMikey]

Negative Side Discharge

Looks like your thumpen the battery's pretty good with pos energy. I have not really studied battery's that much, maybe this is what they need.

It would be interesting to see how they would react to a pos and neg dump.

Hey Dave

This thread has been great. Much input has got my hopes back up again Gotta git ready for the let down

Now let's talk energy. I am dumping to the neg terminal and I can go to a 40 amp plus discharge of pos energy to the neg side.

Those large batteries never get even slightly warm. I ran down one of those big beauties last night to 12.2vdc and today the discharge that they are receiving has been excepted much more readily than ever before.

I am very excited about the way these batteries run and charge so well.

There is no heat on these 6 devices so i am thrilled about that.

You see the capacitor bank is the biggest that anyone has shown on the web for hitting a battery with and on top of that everyone thinks they know what I need to use for a circuit to discharge them.

I didn't know that is for sure and like Matt said I need to learn to calculate. Well I know how to calculate and end up doing some after getting into the ball park.

So far what I am learning "that I like the sound of" is using more capacitance to fire the gates of fets. I am looking around at the websites for stuff. Matt answered one of my questions super good.

Matt said one thing and I said another and it went like this.

I said I wanted to build a 12 device parallel dump with mosfets not knowing which way would be best.

Matt said "Basically" "If I read Matt right" he said that using many drivers is the best way to cut down on heat.

I wanted to fire 6 - 12 devices with a single driver. Of course we are not really just talking about this dump, because I want to employ these chips to drive an inverter? 2 stage?

Yeah thats right I think 2 stage "Cheers to Matt" that last post blew me away with the circuit with 3 coils one wound ccw and the other 2 cw?

Let me know if you build one after supper. I could do it with 2n2222 and a 2n3906 maybe or some small transistors.

I think the cap at the top represents the cap bank?

Anyway back to my dumping (Had to get all that off my mind first)

The battery I am slugging is over 1000ah with a tiny little pulse of energy.

The way I envision the process is like beating a dirty rug on a tree as the only way possible to get it the cleanest. You could sweep the rug with a broom or vacuum it but striking it with the entire weight of the rug impacting and flexing does wonders.

This is my weak description of how much more powerful a cap dump is in cleaning and charging plates at the same time over the process of trickle charging or magnetizing plate.

It is true that once pulse charging has been done and cycles has been accomplished that the battery does go up much faster and does not need so much force to get the job done charging. Less and less should be needed now to charge this completely desulfated battery.

Without the Horse Power batteries are not able to be recovered in a reasonable amount of time. I have through this process of testing going on 2 years, I know what it takes.

I have used small energizers, I have used large energizers ALL on a wide range of true deep cycle AGM converted ALUM.

Nothing and I repeat "NOTHING" can out do a good health punch coming from the proper size unit matched to battery.

Energizers lower resistance so a charge will be excepted and help to recover batteries then GENERATOR MODE will drive them right up.

All energizers MUST and I repeat MUST be hooked to a cap bank first before the battery if you want to keep your battery in one piece. High voltage spikes will destroy any battery if hooked directly to an inductive spiking coil.

Kiss it good bye. So what we learn in our practical application is that batteries WANT and NEED pos energy and POS energy is what comes out of capacitors.

Like Matt said that he wouldn't spend so much time on the dump as he would on how I could charge CAPACITORS, hummm now I see what he means with that last circuit post.

Get the 2x plus recovery to a cap and discharger it in the form that the battery wants "Positive pulse power"

Today the battery went from 12.2vdc to 13vdc in an hour or so. This is the fastest I have seen it charge

Mike

[BroMikey]

Battery size

Notation on Batteries. These batteries were 880ah on acid, their acid trip is over I have learned that upon converting to ALUM that a rating of 880ah will go to 1000ah easily and then after some cycling will increase in capacity.

Today marks the 4th or 5th discharge and recharge cycle for these 2 large 12vdc battery packs. When engaged at a moderate amp draw (say 35-45 amps) these batteries converted to ALUM drop to 12vdc and in an hour sit at 11.7vdc just about all night, well by morning the voltage reading might be 11.6vdc and sometimes 11.5vdc if I ran it harder the night before.

What I am attempting to do in these descriptions or observations is to give others an idea of what to expect out of battery voltage using Alum.

Generally the ACID battery sits 1 volt higher and is fully discharged at 12vdc.

My ALUM batteries work good a 10vdc with not much power drop off but unless you are up for war do not discharge you big battery past 10vdc as it will take seemingly forever to get it back to 15vdc.

With a powerful dump like I am using it is possible otherwise regular chargers would need to be employed at intervals of 12hrs on and 6hrs off using a constant current regulated supply for a long period of time to prevent internal heating and damage.

During long power failures from natural disasters lower powered devices such as radios, TV's, fans and lights could derive their energy from large ALUM battery banks running at lower voltages without hurting the battery.

So whatever power might be harvested from tiny windmills, water wheels or solar cells might charge the ALUM battery and effectively used which is nothing like an ACID battery that suddenly shows power and the next thing you know you are back pedaling again.

Acid batteries sulfate greatly under a lowered voltage condition and often are lost forever unless strenuous measures are taken with endless hours of hoping and praying it revives.

Take it to the dump Or a cap dump and blast it's door off and if it comes back to life drain the ACID and use some of that earth friendly pickle juice known as "AMMONIUM ALUMINUM SULFATE".

Okay now the reason for popping in today. My batteries are at the beginning of cycling using pulsed power and already are taking more energy than at the beginning. Like other batteries that I have worked on the acid would charge right up and the charges would not last long either however fair for acid.

With each cycle acid would get harder to charge but would go right up during a 12 hour period and be full soon after.

With ALUM you must be prepared to see longer and longer charge times as the battery grows in size.

My 100ah AGM 12vdc batteries cost $300 each and after boiling the juice out of these babies with conventional charges, in a few months they only gave me 50ah each. I have two.

So I converted to ALUM and now after conditioning the batteries by pulse charging and discharging for 2 weeks this way they now give me as high as 170ah from each battery. They take 3x as much energy to charge and give it back so my battery is back giving me good service.

I have 15-20 good 30ah AGM converted deep cycle batteries that "ALL" did the very same thing, giving me over 50 percent more power than rated at.

My scooters will take the children much much further with way less problems.

The point is that if you convert to ALUM be ready to wait long longer to get the batteries up to 15 plus volts DC.

Right now I pulse 1 of these batteries all night then all day and discharge it at varying rates for 12 hrs. Today my other battery is not quite full so I charge them both all day together so i will still be ready tonight for discharge.

Once in a while at this interval I stop the pulse charging because the voltages will not rise over a 6hr period for lack of ALUM plate forming especially if I have discharged the battery a little further than the last time.

Still I will not form the plates long, either I will pulse AND trickle charge or I will stop pulsing and run at a 10-12 amp input for one hour and revert back to pulse dumping.

There is no shame in using regular current at low levels to reform newly converted cells as both pulsed currents, continuous currents are compatible what a battery needs. It is part of a process that I have done 100's of times yet you will find no mention of this anywhere I can find on the web or any book.

Without DIRECT CURRENT charging there would be no batteries.

Be ready for WAR

Mike

[BroMikey]

Battery Voltage

Okay update on the big batteries. The voltage has been running all night at about 11.6vdc these are ALUM batteries 880ah now converted and 1000ah.

Now one of the batteries (As of last night) is discharging at around 11.9vdc so the conditioning is paying off.

That would mean that to get them back down to a voltage of 11.6vdc I would have to run power all night for two nights instead of one. The voltage drop for on night is about 2 points from say 11.8 to 11.6vdc before and now 12.1 to 11.9vdc.

Point in case: The batteries are growing in capacity.

Mike

[Dave45]

A Half Bridge Buck Boost Converter with high side N-type MOSFET

[BroMikey]

Why?

A Half Bridge Buck Boost Converter with high side N-type MOSFET

Why are you interested in the application of "buck boost" topology?

Is there some way of using this idea with coils to recover energy? Or what?

Mike

[BroMikey]

Progress report of Dump Circuit.

I am back with an update that my transistor blew up Remember I have six of them? I am running extreme power into of surging voltages and amp fluctuation plus 100 degree heat in the room.

No mercy, 100vdc input at 7-12 amp fluctuating on input side. 3 ohm resistor to run all of the power through to the cap bank.

Output side 35 amp pulses 3 times per second.

3 Days later one FET is shorted.

Fet temps were 125 degrees for 3 days.

Conclusion:

(1) Six Fets are not enough to handle this much power.

(2) Poor steering of gates produces heating

(3) Poor steering and not enough fets? BOTH?

When reconsidering I would have to say that each fet might be capable of 3 amps of surging high voltage. This fet is rated at 280 watt max burnout.

SO let us say that each fet rated max 280 watts is good for 200 watts all day long 365 days 24/7.

I have not put my thinking cap on much till things burnout.

I am passing 35 amp pulses using 6 parallel IRFP460 FETS.

This divided up evenly = 6 amps per FET and since each Fet is also passing voltage with it we must multiple 80vdc X 6 Amps = 480 watts in 250 mS. That is 480 watts EACH so X 6 =2800 watts.

So we can C that my poor little darlins are smoking da junctions cause I didn't do the math

Now like I said if I keep power levels down I can run for weeks on end with no heating and have done that but my huge battery won't charge up for days either.

12 Fets were my goal but I just had to try it with these used FETS Used FETS? Used? Yup Used. I accidentally bought these FETS one night half asleep and didn't notice that they were used until I went back and looked at the EBAY purchase order.

Some of you may have remembered a comment I made about broken base (gate) legs that I soldered back on. These were brittle and I couldn't figure it out.
I had never heard of such a thing as selling fets used for the same price as new ones.

I have the new one's now, but that really is not the point is it?

Now I know some of you are going to jump up and say that I should be running a 40-50 percent duty and this would put me right near the line on designing for watt handling.

I am thinking 3 amps each at 80 vdc is (240 watts) a max rating for my design not wanting to go all of the way to 280 watts and wanting even more ceiling. hum thinking.

12 Fets maxing out at 3 amps each is 12 X 3 = 36 amp pulses

So 12 fets will just barely do this job at Max input and output. So guess what? Gonna take away all of the excuses why it might be over heating by using the TL594 to driver TC4420 To two FETS each.

You can use a 555 timer and a 556 dual timer or why not use a 594 well a tl594 they call it. It's a more accurate chip for higher output levels and the reason you need more accuracy at elevated power levels is that every deviation causes more friction.

It is like trying to run the Gran Prix with a loose tie-rod end on the steering of your front wheel. At 30 miles an hour everything seems normal and at 70 MPH the front end won't shake that bad bad run it up to 250MPH and you got big trouble.

It is time to use the math now that I have burned up most of my used FETS.

My Fets collectively passed 35 amp pulses at 80 vdc for 2 days this is 35 X 80 = 2800 watts of power. These used FETS should handle 240 watts max so this is 3 amps each for six FETS is 18 amps collectively and is 18 X 80 = 1440 watts

So we should all be seeing that the fets are rated at 1440 watts max handing and I am running 2800 watts through them for only 2 days.

Mike

[Farmhand]

BroMikey, I think you are confusing power dissipation by the mosfet itself and
the current the mosfet can pass at 500 volts.

If we multiply 500 volts rated mosfet by 20 Amperes then that's 10,000 Watts.

The Maximum power dissipation I think is how much thermal power the mosfet
can "get rid of" without failing.

The most likely reason for those mosfets to fail would improper turning fully
"on" and holding "on" of the mosfets creating a high resistance in the switch
for some of the current or over "pulsed" current limits. If the mosfet has to try
to "get rid of" more than 250 Watts average then it'll struggle.

If the mosfet turns on quickly and the resistance of the mosfet is very low very
fast and stays very low resistance while the current flows then the mosfet
should not get that hot.

Another problem might be from stray inductace causing high voltage spikes
and ringing at over the voltage rating of the mosfet.

Basically 1 x 100 volt- 30 amp part like a IRF540N should be able to pulse a
battery with about 30 amps as long as the peak currents are not exceeded
and the breakdown voltage is not exceeded.

With some protection from high voltage spikes at the mosfet drain you should
be able to use even lower "on" resistance parts like the IRF1405.
Rated at 169 amps continuous current and 680 Amperes pulsed current. Just
one part with some precautions to protect it from any stray voltage spikes. Bingo.

Note the input capacitance of this part is quite large, and would still require
being driven well to achieve those ratings in operation.

330 Watts maximum power dissipation and 55 volts x 169 amperes is 9295 Watts
it can handle in switching. And it's a smaller TO220 part. Use a heat sink and
damp the spikes at the mosfet drain.

http://www.jaycar.com.au/products_uploaded/zt-2468.pdf

..

[BroMikey]

Thanks for speaking out.

BroMikey, I think you are confusing power dissipation by the mosfet itself and
the current the mosfet can pass at 500 volts.

If we multiply 500 volts rated mosfet by 20 Amperes then that's 10,000 Watts.

The Maximum power dissipation I think is how much thermal power the mosfet
can "get rid of" without failing.

The most likely reason for those mosfets to fail would improper turning fully
"on" and holding "on" of the mosfets creating a high resistance in the switch
for some of the current or over "pulsed" current limits. If the mosfet has to try
to "get rid of" more than 250 Watts average then it'll struggle.

If the mosfet turns on quickly and the resistance of the mosfet is very low very
fast and stays very low resistance while the current flows then the mosfet
should not get that hot.

Another problem might be from stray inductace causing high voltage spikes
and ringing at over the voltage rating of the mosfet.

Basically 1 x 100 volt- 30 amp part like a IRF540N should be able to pulse a
battery with about 30 amps as long as the peak currents are not exceeded
and the breakdown voltage is not exceeded.

With some protection from high voltage spikes at the mosfet drain you should
be able to use even lower "on" resistance parts like the IRF1405.
Rated at 169 amps continuous current and 680 Amperes pulsed current. Just
one part with some precautions to protect it from any stray voltage spikes. Bingo.

Note the input capacitance of this part is quite large, and would still require
being driven well to achieve those ratings in operation.

330 Watts maximum power dissipation and 55 volts x 169 amperes is 9295 Watts
it can handle in switching. And it's a smaller TO220 part. Use a heat sink and
damp the spikes at the mosfet drain.

http://www.jaycar.com.au/products_uploaded/zt-2468.pdf

..

Hello Farmhand

I want to thank you for pointing some of these basics out. Here is what you are saying. You just said I can take all of the 14awg copper leads on all 24 banks on my capacitors that twist up to measure the size of battery cables on your car and pass all of the current through a 16awg leg on a single transistor.

See the way I look at it? I have a 2awg collection of terminals minimum and you want me to pass all of that from emitter to collector using one part?

I am looking at this cap bank based on how the pathways offer resistance to the pulses.

Strictly common sense that if you have a single transistor that has a physical leg size of 16-14awg then it does not make good sense to try to pass the current through that part coming from a conductor the size of your finger.

I am not looking at this from a math prospective, just simple pathways.


Please explain your reasoning here.

Mike

[BroMikey]

Engineering Jargon

You see when Farmhand talks about a tiny part switching 160 amps it is a technical marvel but only applies to a micro second rating.

All of the graphs show that a device at 77 degrees can throw alot of amps for say 50-100 micro-seconds. And then if the process is repeated this is called the "repetitive" rating and drops. Then if the "TIME" goes beyond to say double 200 microseconds the amp handling goes way way down.

Switch mode power supplies work well with high frequency pass transformer and oscillations of the FET can do wonders.

In my case as the "TIME" is extended to 300 mili-seconds the Fet can no longer pass it's maximum value. A good way to understand what a cap dump needs in terms of power handling is to do this.

Take a large battery charger and charge a battery with it at a rate of 20 amps but do this through a MOSFET that is fully turned on. After several seconds the device will begin smoking.

I visualize my capacitor wires like channels of a river all coming together into one large canal. Now I want to break up my stream into small branches for redistribution.

The small branches are my FETS processing the flow coming from the canal.

In my case it looks like 12 FETs will be enough to absorb the flow of energy and then pass the power into another location. If my branches are not big enough then the pressure and force increases as the canal is much bigger and is over powering these pathways.

Water pressure and electrical pressures can resistance and damage.

Take John Bedini tesla tracker 5. John uses 24 16 amp rated devices to pass 200 amps. The max rate is 380 amps approx. Plus 200 amps is never reached during the machines operation.

John B Track 5 is using large wire and the way to figure is by common rules. A conductor can only pass so much and if each tiny leg of 24 devices adds up to a 200 amp wire size, you have just figured out how to size things.

I chaet, I watch and follow the best.

Mike

Mike

[BroMikey]

160 amp device

I am correcting my last post of 200 amps. The tracker 5 I am looking at is a 160 amp unit for driving raw wattage into batteries like sound amps do to speakers.

This tracker operation is a cool subject.

Look close in the video. John uses 16 amp PNP devices. There are 24 of them for a max amp handling of 380 amps but JOHN never runs them over half of that for MAX and MAX output is rarely ever reached with any good setup.

https://www.youtube.com/watch?v=y93IwhOGWB4

Am I getting through?

24 huge power transistor twice the mass of these FETS.

24 devices at 8 amps each oscillating at whatever frec adds up to 192 amp handling AT 38vdc.

So at 100vdc the same setup might only be good for 3 amps for each Transistor.

Does anyone know that a cap dump is not operating in microseconds>

This beasty is on for 300mS 3 times per second the rise is a few "uS" that is "MICROSECOND" so the dump is always on for the most part.

A dump should be rated the same way continuous power flow ratings are made like a contractor application.

It is off some but mostly always on and dumping. Off time is very few mS "MILISECONDS" during the length of 1000 miliseconds.

Am I reaching anyone?

Mike

[Farmhand]

No the rating for the IRFP460 is 20 amperes for continuous source to
drain current and 80 amperes for pulsed source to drain current, however we
can't expect to reach those values without at least passive cooling with heat
sinks or possibly with active cooling (fans). If not going over 100 volts applied
why the need for a 500 volt part ?

Mosfets can switch DC so that it flows continuously for however long is desired.
They have a continuous current rating.

IRFP460 pdf, IRFP460 description, IRFP460 datasheets, IRFP460 view ::: ALLDATASHEET :::

The current and voltage ratings are only related in that a higher voltage will
cause a higher current through a given resistance. So if you apply 500 volts
to a 5 Ohm load through an IRFP460 then the current rating will be exceeded.
All of them. A higher voltage part will not help deal with more current.

I found that once I could reliably switch the mosfets all the way on and all
the way off quickly then I could make the mosfets handle a lot more power
with less heating.

Have you got a gate drive wave form to look at ?


Cheers

[BroMikey]

No the rating for the IRFP460 is 20 amperes for continuous source to
drain current and 80 amperes for pulsed source to drain current, however we
can't expect to reach those values without at least passive cooling with heat
sinks or possibly with active cooling (fans). If not going over 100 volts applied
why the need for a 500 volt part ?


I found that once I could reliably switch the mosfets all the way on and all
the way off quickly then I could make the mosfets handle a lot more power
with less heating.

Have you got a gate drive wave form to look at ?


Cheers

Hello Farmhand

Thank you for reaffirming what I need to hear that like you said above, MOSFET HANDLING A LOT MORE POWER.

No I don't have the wave shape just yet it is coming. I am out in the burning sun working on AC units ETC.....................................

Last Night I did some calculations for a switchable 1,2 3, and 4 pulses per second. I am going with a 100uf cap and resistance is 4000, 6000, 8000 ohms if I remember right but been dragging my feet making sure I do things right cause i never tried this one before.

To answer your question as to why I went from a 200v device up to a 500 volt device is in the industrial applications handbook by I think ONSEMI.

The handbook says 200v and 250volt devices are good up to a max of 70 volts and that these 200v and 250volt devices are generally operated best in the 50 volt range.

I was looking around to try and understand why my 200volt fets were blowing at 70-80vdc and the handbook also said that for industrial designs 80vdc and above were more stable and performed longer using the next step up in device voltages being a 500vdc ceiling.

Also it was brought to my attention that a cap dump to battery often produces a reflected voltage surge of up to 3X the dumped voltage and did explain why unexpectedly even running at low power level these lower voltage parts failed.

Also I am using to large coils of wire in the form of 2 separate toroid's, one a variac and the other a 3kva size step down. As the caps are filled and dumped the coils surge right along with the process. Inductive surging can cause voltage fluctuation.

So with all of this in mind I decided to go with a higher voltage rating of 500vdc. It was a great move because now i can go for weeks or months running a 300-500 watt input where before those input levels would make short work of my devices.

I have come along way in the last month learning by burning FETS out.

The only way I could burn out this last set of 6 FET's and I was trying to. Was to max out my supply at 100vdc using a surging amp draw from 7-12 amps. I left it in a 100 degree room for 2 days waiting for the moment of truth BOOM!!!! a straight shot to the supply at 5amps.

Oh yeah one more thing I need to say about device voltages and current ratings. A 500vdc max ceiling generally is operated at around 100-150vdc but will not be able to run the full amp rating. The full amp rating is often shown at a 10volt or 30-50vdc range so these ratings change with the weather. So unless you specify exact application and show the actual device operating I wouldn't even guess at how many amps a 20 amp device might be good for. Well if I guessed I would say more like stay within a temp range measuring while it runs and turn it down. Only then will you know for each application.

Ball Park: A device capable of passing 280 watts operating as an oscillator like in a PC power supply will have a rating of 30amps at 500vdc and this should give folks some sort of example for applications that target longevity.


Anyway my FETS were all running far over their max. I pushed them to 380 watts each which is near double what they should be operated at.

Thanks for staying there till I make the grade on this step up in steering gates. It is good to have someone remind me that the new circuit will be better.

And yes a wave form will be posted for your review.

Till then I have a million questions but won't bore everyone just yet.

Mike

[Farmhand]

I've been busy making some shots and pictures for you, I'll go back and read
the posts I missed soon.

Here below is a circuit I tried tonight, I used 26 volts dumped in a 250 mS
dump time with 500 mS recharge for the dump caps. The 45,000 uF caps had
not fully discharged in 250 mS, There was still about 2 volts and some current
when the mosfet turned off.

I got about 13 Amps peak current on dumping that declines. The current
sense resistor is 0.8 Ohms and it got hot but the mosfet stayed cool to the
touch. Maybe if you put a 0.5 Ohm resistor in series with the mosfets Sources
it might help.

Also

Shot 1) is the wave form of the applied voltage in blue and current yellow. Note
the voltage scale and the yellow voltage is divided by 0.8 to get amps through the battery.

Shot 2) is the voltage on the supply caps and the dump caps. Note the dump
caps drop voltage and this reduces the current a lot before switch off.

Shot 3) is my gate wave form taken on the gate while working.

Shot 4) is the fall time of the gate voltage. This allows the turn off with
current still flowing without excessive heating, because the cap was not fully discharged.

This indicates 2 Ohms resistance in the discharge path, if I took out the 0.8 Ohms
current sense resistor the peak current would be more like 21 Amperes. I think

Cheers

P.S. If I put my ear near the wire to or from the battery or near the mosfet I
can hear an audible tick....tick....tick in the mosfet and wires, it sounds like a
spark plug sparking, but it is a good sound, the sound of shock and awe,
If I was to scope different parts of the wires I would see ringing at HF probably.

In cicuits that switch randomly like my solar circuit the clicking sound becomes a jittering buzz,
like a code or logic language.

..

2nd P.S We can see by the initial voltage and the initial current on discharge
that 26 volts x 13 amperes = 338 Watts applied initially to the battery, but
declining, the circuit is drawing a fluctuating power of between 25 and 65 Watts from the wall socket.

Actually, maybe the battery voltage needs to be subtracted from the 26 volts cap voltage for some calculations.

...

And the coil I used with 2.7 Ohms resistance got real hot so need more
inductance and less resistance in the coil, maybe a MOT primary would work.

[BroMikey]

Nice Test Dude

I've been busy making some shots and pictures for you, I'll go back and read
the posts I missed soon.

Here below is a circuit I tried tonight, I used 26 volts dumped in a 250 mS
dump time with 500 mS recharge for the dump caps. The 45,000 uF caps had
not fully discharged in 250 mS, There was still about 2 volts and some current
when the mosfet turned off.

I got about 13 Amps peak current on dumping that declines. The current
sense resistor is 0.8 Ohms and it got hot but the mosfet stayed cool to the
touch. Maybe if you put a 0.5 Ohm resistor in series with the mosfets Sources
it might help.

Also

Shot 1) is the wave form of the applied voltage in blue and current yellow. Note
the voltage scale and the yellow voltage is divided by 0.8 to get amps through the battery.

Shot 2) is the voltage on the supply caps and the dump caps. Note the dump
caps drop voltage and this reduces the current a lot before switch off.

Shot 3) is my gate wave form taken on the gate while working.

Shot 4) is the fall time of the gate voltage. This allows the turn off with
current still flowing without excessive heating, because the cap was not fully discharged.

This indicates 2 Ohms resistance in the discharge path, if I took out the 0.8 Ohms
current sense resistor the peak current would be more like 21 Amperes. I think

Cheers

P.S. If I put my ear near the wire to or from the battery or near the mosfet I
can hear an audible tick....tick....tick in the mosfet and wires, it sounds like a
spark plug sparking, but it is a good sound, the sound of shock and awe,
If I was to scope different parts of the wires I would see ringing at HF probably.

In cicuits that switch randomly like my solar circuit the clicking sound becomes a jittering buzz,
like a code or logic language.

..

2nd P.S We can see by the initial voltage and the initial current on discharge
that 26 volts x 13 amperes = 338 Watts applied initially to the battery, but
declining, the circuit is drawing a fluctuating power of between 25 and 65 Watts from the wall socket.

Actually, maybe the battery voltage needs to be subtracted from the 26 volts cap voltage for some calculations.

...

And the coil I used with 2.7 Ohms resistance got real hot so need more
inductance and less resistance in the coil, maybe a MOT primary would work.

Pretty tricky Farmhand

I am learning something new putting in coils of high wattage in the place you show. Now I get it so the heat goes to the coil and not the MOSFET.

Nice waveforms, lots of good work, what a man. So this way a coil could save the FETS. Plus a coil done right won't burn the energy just slow if and store it. Humm....? I don't know.

You have got the wheels turning. I like the looks of your driver board.

My input is 1000 watts. I charge my cap bank to 100vdc and 3 pulses per second empties the bank beginning at 65-70vdc and down to 36vdc so I am operating so fast it is like an always "ON" condition. Very little rest interval. 3 pulses dumping with each pulse taking 300mS to discharge so 50mS charge up time.

Me bee smokin dem fets

Waveform 1-4 is very interesting. I am glad to see these because I am not sure how to do it over here.

Mike

[Farmhand]

yeah you got it, kinda, the coils inductance slows the flow of current from the
supply to the dump caps, I'm using smoothing caps because I 'm using a
transformer, I can't setup a large setup like yours but I can set up a smaller version.

So with the right coil between the supply and the dump caps and the right
"on" time and "off" time we should be able to get down to almost zero current
at switch off due to the coil storing the energy and causing the dump cap to
drop voltage without drawing directly from the supply during the dump time,
the dump caps fill when the switch is off because the coils "momentum"
causes it to discharge into the dump caps due to the switch turning off.

The intention isn't to heat up the coil or anything and a coil with less
resistance but a with the appropriate inductance is better.

I'm now using a microwave oven transformer primary, and with 30,000 uF I
can get the cap to fully discharge in around 70 mS or less which leads to an
almost no current situation at switch off. it takes about 350 mS to recharge
the cap and it goes to a slightly higher voltage due to the storage of energy
in the big coil. The peak current is the same if the voltage is the same and
the resistance of the current path on discharge is the same. This is a way to
isolate the supply from the load during the dump without using a second
switch "except for the diode".

I'll include some shots of the action of the voltage on the caps in that mode.
as well as a shot of the applied voltage and resulting current when the
discharge is short and the capacitor does not get fully discharged.

The coil and dump cap is a "resonant charging circuit" but it is very low "Q"
being so low a frequency. I can do from about 1 per second to about three
per second and keep a voltage rise on the dump caps.

Also if you put the capacitance and inductance in this calculator it will tell
you the resonant frequency of the two together which will tell how much
inductance is required for a given capacitance to get a certain frequency.

Resonant frequency calculator
Resonant Frequency Calculator

The first shot shows the supply capacitor voltage in blue and the dump cap
voltage in yellow, as the mosfet turns on the dump cap discharges but no
current flows directly from the supply to the load due to the coil causing a
delay and storing energy, which is released when the mosfet turns off.

Second shot shows the applied voltage and resultant current when the
mosfet is switched on and off before the cap can discharge, this requires a
fast turn off to do without excessive heating of the switch.
This shot shows the circuit working at 400 Hz and pulsing the battery with 10 Amp
rectangles of current for 260 uS, it's 400 Hz 10% duty, That really pumped up the battery.

Cheers