Cap Dump Circuit

[BroMikey]

Radiant Cap charger

Here is a radiant Oscillator in forced MODE charging caps for dumping. The cap dumps operate at a higher efficiency when used together.

You can that his diagram.

Powerful Single Coil Radiant Charger by Sul-Tech - YouTube

This is very simple stuff, almost anyone can do.

600 miliamps at 19vdc is 11 watts that charges a 1000uf cap to 220vdc in seconds.

With an Oscillator like this filling capacitors a large battery can easily be charged from a tiny input.

I have used these Oscillators to fill caps in a cap dump circuit and watched the scope while the discharge occurs.

The Oscillator goes out of tuning for a few microseconds lowering it's output almost completely, when the dump takes place and this is best. There are other ways to turn off the supply to a cap dump momentarily like to employ a Mosfet switch controlled by a microprocessor based chip.

This radiant method (Bedini Forced Oscillator) of charging capacitors is more efficient and should also have some form of over voltage shutdown circuitry to protect the Oscillator if batteries fail to receive a charge or short out.

Either way capacitors are charged more advanced circuits are needed to perform a practical application than proof of concept.


If batteries are ever accidentally hooked up backwards circuits can be added to prevent this.
Simple Way To Prevent DC Reverse Polarity - YouTube

Mike

[BroMikey]

Testing Phase

Continuing on with my progress I have ordered and installed all new Mosfet's and have shelved the IRFP250n Mosfets as they can not be used long term to pulse charge more than a 24vdc battery bank. Anything over 60vdc and up to 75vdc will randomly trash your project due to reflected back spikes.

This is not an oscillator. This is not a CLAMPED capacitor discharging circuit.

This is a circuit that welcomes some ringing and therefore MUST use a higher voltages rate HEXFET.

I will proceed no further til I am completely sure why I have blown dozens of FETS. I am getting very comfortable with my HEXFETS.

My silly drive circuit offers only a ms rise time and fall time and when using IRFP250's over 50volts they get hot fast under any kind of even a medium load as specified by the manufacture. This is because of the way my circuit is made so as not to eliminate ringing.

I have an adjustable supply 0-100vdc @30 amps that has a fan on both the variac and rectifier sink. It is hooked to a regular wall plug that will max out at 90vdc @20 amps so I can't turn it all of the way up.

I have 3 devices running for days now, they are the new IRFP450 FETS. I have pulsed these Mosfets up to 500 watts of repetitive discharges that go like this.

A single pulse is showing 20 amps and will actually be some larger value.

Pushing the duty and frec's to around 6hz @50 percent these 3 devices heat up about 8 degrees about room temp in 2-4 minutes without running the fan yet.

They can handle 90vdc all day long with a slow rise and fall time so I am finding out day after day that these part are going to do the job.

I will now add the remainder of my devices, 9 more.

Next will be the addition of the fast driving circuits. 6 drivers TC4420 6amp each driving 12 FETS, 2 fets per driver chip. I am looking at the idea of using heatsinks on my driver chips.

The one unknown is will a single TL594 power up 6 TC4420 drivers?

Mike

[BroMikey]

Pathetic Waveform

One more thing I have final learned tonight about my dumps. Let me say that I have been learning how to work this fancy scope (HP54100D) and tonight for the first time I realized that the way I had been previously viewing my wave forms is incorrect.

I am learning to use the "Magnify" function with this controls like "Offset" and "Vdiv" and fooled myself.

So you see the hundreds of hours of using this scope is paying off.

My waveform is a SAWTOOTH. This is one of the first waveforms all beginners generate. Turning off the Direct Current and then back on again.

I can see now that this sort of pulse is not going to compare at all to the latest rise and fall times associated with more modern topology.

Obviously this is good bye to the old way as this version for beginners started 100 years ago. I never realize how embarrassing this design actually looked on the scope til today.

Here she is, slower than molasses in January. Hilarious

But it works That is the funny part. Oh and real easy to build.



Mike

[BroMikey]

3Capacitor discharging Units

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

This is how I have built 3 dumps



Mike

[BroMikey]

Negative

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

Hey Farmhand I am 56yrs

My desire to do more electronix has blossomed these past few years.

I use the far right hand terminal source to bring in the negative side of my cap bank so my red wire goes directly from the cap hot to the battery hot.

So I pulse the negative wire. Is this good?

Mike

[Farmhand]

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

[BroMikey]

Great Information

Disregarding the power dissipated by the switch due to slow rise and fall times I
think the following holds true.

Basically with a total Capacitor dump the rise time of the driving pulse which is the
close time of the switch is most important in order to begin max current flow
quickly.

But with a coil discharge the fall time of the driving pulse which is the opening
time of the switch is more important in order to collapse the magnetic field
quicker, which in turn causes a fast voltage rise from the coil discharge.

..

Thanks A Million Farmhand

You have no idea what this kind of instruction means to me. That is a great circuit. I will keep it. I will ponder this circuit as I grow in confidence.

I had an old man 80years in the hood come to me saying his only transportation had failed him. It is a 36vdc scooter using 3 batteries in series 12ah each so this was my big chance.

I can effectively discharge at 90vdc. One batteries cracked and went bye bye. I had a replacement all conditioned and ready for the show. The other two were getting warm and I had to stop. They all charged up one at a time and together as well but you know how it is, only up 14plus volts, not the best.

But since I lost my big SG OSC I almost forgot how much it is needed. I have two others. Anyway the heat kept building and I realized after your post that my mind was not on the chemical aspect as it should have been.

I have been all through this time and time again. I just put 1 on the SG OSC at 10 watts, thanks

I just wasn't thinking when I said that cap dumping is good enough.

She was warming up and I know I have to cool it before proceeding. I usually wait 20 minute to an hour depending the size.

You guys are a great help and I want to thank you for popping in like this and correcting my path.

Encouragement is a powerful word. I am looking at the pixane controller and thinking.........Hummm..................do I need to pull out my code books???....Humm..............

Mike

[Farmhand]

Disregarding the power dissipated by the switch due to slow rise and fall times I
think the following holds true.

Basically with a total Capacitor dump the rise time of the driving pulse which is the
close time of the switch is most important in order to begin max current flow
quickly.

But with a coil discharge the fall time of the driving pulse which is the opening
time of the switch is more important in order to collapse the magnetic field
quicker, which in turn causes a fast voltage rise from the coil discharge.

..

[Farmhand]

The question is very specific to pulse charging batteries and maybe this is a subject that is out dated. I know what Tesla said but I wondered if anyone else pulse charges batteries with home made circuits? Or is everyone buying their pulse chargers pre-made?

Again the question:

If I pulse charge a battery using a rise time of 1ms at 500ms duration and then fall 25ms

What is the major difference if I use a 100ns rise and 500ms duration then a 200ns fall time.

Okay you have the question with it's two possibly rise and fall times.

The question is what does the battery see that is different?

Does it charge faster with less input?

Does a faster rise time only save on mosfet's and the battery doesn't care?

Just wondered if anyone else has asked these questions other than John Bedini.

I quess not to many huh?

Mike

Hi Bromikey, Here is some words below in "quote" from a guy who due to unfortunate
circumstances cannot post here any more. I also attach the circuit I made up
for conditioning batteries. I don't think I posted it yet.

The question of rise and fall times is good. The actual rise and fall times cause
a period of resistance change through the switch from high to very low, the
faster the rise and fall times the less energy is dissipated by the switch resistance.

Currently I am experimenting with a feedback oscillator driving a resonant air
core transformer, it has one mosfet driven by a mosfet driver which is
triggered by a feedback signal that is processed through a small transistor and
an inverter/buffer.

Rise and fall times are matched at about 50 nanoseconds each with that
driver chip and mosfet, IRF740, at 840 kHz.

One thing to note is that if the coil is switched on for too long then it can be
fully charged and current will flow through it to ground at loss, it's best to
keep the on time to the coil so that the coil is charged and switched off when
the magnetic energy stored in it's field is maximum or close.

Inductor power calculator.
Inductor Current and Maximum Power Calculator

As far as the coils magnetic field energy release, then Mario explained it well,
but I would add that the fall time is the important one for getting a good
discharge, however both are important as the rate of change is relative to the
magnitude of the voltage developed, in some circuits rise and fall times too
fast cause problems better avoided, but for DC-DC converters and cap
dumping the faster the switch works the better.

They way I see it due to impedance matching to charge a battery with
pulses only double the battery voltage is required, there is a optimum
impedance match for maximum energy transfer on each different battery/type.

Conditioning batteries is much the same except it is generally accepted that
desulfation takes time to do it's thing, and if too much power is used the
battery can be damaged or overheated while it's resistance is high. Most
batteries badly sulfated can be better desulfated with less than 10 Watts
applied in 24 volt or so pulses at a higher frequency up to a few kHz. Lower
frequencies work but take longer.

My circuit is designed to do both desulfation and charging based on a solar input that varies in power and voltage.

However it can be used with a 12 volt battery for the supply where it will
then use one mosfet "Q2" as a boost converter to charge C2 cap to whatever
voltage is programmed then "Q1" dumps the increased voltage to the battery,
in a series of 10 to 20 microsecond pulse trains. It pauses the boost
converter while the cap dumps happen.

With solar input it's programmed to pulse the battery so as to keep the solar
input at it's max power voltage of 17 volts if solar input goes less than 17 volts
then the boost kicks in and 24 volt conditioning pulses are supplied to the battery.

If you want to dump a large capacitor with a lot of charge into a battery and
have it discharge fully then the time the discharge takes will vary depending
on different things, still it is not desirable for the switch to turn off slowly if
the current is flowing, if no current is flowing it doesn't matter how long it
takes to turn the switch off.

Quote from Poster SeaMonkey at OU.com

Rapid rise times and short time durations of
pulses applied to the lead acid battery are
most effective for desulfation. The very sharp
and short pulses reach the lead sulfate crystals
with maximum effect and cause them to be
converted chemically back into active plate materials
and renewed sulfuric acid in the electrolyte solution

Longer pulses with not so sharp rise times are most
effective for charging the battery and less effective
for desulfating and restoring batteries.

The very short and sharp pulses get the desulfation done
with such low average power that the battery isn't
dangerously overheated or caused to gas excessively
as the desulfation nears completion.

Longer pulses would result in higher average power into
the battery and can cause overheating as the battery
being charged transitions from bulk charge into finishing
charge. Even a good battery can be overheated if the
finishing charge rate is too great. It is during the finishing
charge segment of the charging regimen that gassing will
occur and if it is too violent because of excessive charging
current the battery can be damaged.

Batteries which are in very good condition can be charged
with long pulses for the entire bulk charge process, then
the pulses should be shortened or reduced in frequency
in order to accomplish the finishing charge.

Sulfated batteries which are not in good condition should
be desulfated with very short pulses which are very sharp
to limit the power put into the battery during this process.
Desulfation releases considerable heat as the lead sulfate
crystals are chemically converted back into active plate
materials and sulfuric acid, and it is essential that the battery
not be overheated to avoid permanent damage.

One other note is that dumping too high of a voltage into a battery can
cause it to spark internally and explode. Particularly if the batter is or
becomes damaged.

Cheers

[BroMikey]

Better all around

Hi Mario

Thanks for your help I really need right now. I find very little on this subject even on the most technical sites. It is a much appreciated post.

I can understand what you are saying but it is always nice to hear confirmation. No one need correct you WITH ON TIME and mosfet heating in the form of resistance.

The scope I am using shows no tapering curve for ON TIME only slow 24ms off times.

Still the square wave looked fairly straight up and down and even with this very slow rise I have always used, I have gotten excellent results.

I am looking forward to seeing what the faster speed is like. Tesla stated many things about pulse time and duration so making circuits that give options is an exciting addition.

Thanks Mario for kicking in what you know to be true about both electronics AND the effects with radiant.

Mike

[Mario]

[BroMikey]

IRFP450 Mosfet

I also told you guys I would let you know about pulsing higher voltages. If you did not know the IRFP250 is the forwarded device used by those who cap dump batteries or supposed to have.

The IRFP250 can not pulse charge a 36vdc bank of batteries because they blow in minutes from back spikes or reflected energy.

On the other hand the IRFP450 has a 500volt ceiling not a 250v.

These 3 devices are running 90vdc all day and they never get hot.

So buy IRFP450 Mosfet's for pulsing 100volts.

Mike

[BroMikey]

Hard questions

The question is very specific to pulse charging batteries and maybe this is a subject that is out dated. I know what Tesla said but I wondered if anyone else pulse charges batteries with home made circuits? Or is everyone buying their pulse chargers pre-made?

Again the question:

If I pulse charge a battery using a rise time of 1ms at 500ms duration and then fall 25ms

What is the major difference if I use a 100ns rise and 500ms duration then a 200ns fall time.

Okay you have the question with it's two possibly rise and fall times.

The question is what does the battery see that is different?

Does it charge faster with less input?

Does a faster rise time only save on mosfet's and the battery doesn't care?

Just wondered if anyone else has asked these questions other than John Bedini.

I quess not to many huh?

Mike

[BroMikey]

Rise times Benefits

If possible maybe someone could answer what the benefits of increased rise time switching for pulse charging a battery. Does fast rise save on power and heat of the mosfet only or does the faster rise times charge batteries better?

Thanks, Mike

[BroMikey]

Parts in the Mail Came

Okay some of my parts came and 3 of these IRFP450's have been pulsing for days. I am using a 14awg wire on both switching legs right now i have 3 mosfets running. This makes 1/4 of my final circuit.

I am using a thermo probe laying it on the device and right now with all 3 parts, the temp is 2 degrees higher than the room temp switching very low power.

I am not using a fan yet. Look a few posts back and you can see my heat sink.

I am running 4-5amp pulses by sending 24vdc to a 48,000uf cap with batteries behind the cap. The batteries charge the cap through a 3 ohm resistor so huge split second charging surges to not further warm up my devices.

Also a large wall adapter producing only 26vdc is charging the batteries THRU a resistor of 4 ohms so powerful amp swings do not cause part heating and low efficiency.

The rise time is 1.5 ms and the fall is 24 ms and in light of the fact that the duration is 250ms the rise and fall time look straight up and down on the scope.

Question.

If I shorten the rise time to 1 uS and the fall to 6 uS and keep the duration at 250ms what significantly different effect will I have on charging batteries???

Will this shorter time for rise and fall make for more or less heat generation on the devices????

I know the faster rise will show higher amp surges on the meters, but is that significant?????

Of course this question is only for those who have pulse charged batteries using more advanced method's than using automotive turn signal relays for switching.

Mike

If possible maybe someone could answer what the benefits of increase rise time switching for pulse charging a battery.

Thanks, Mike