Cap Dump Circuit

[BroMikey]

Nice machine

Great example Dave

Mike

[Dave45]

The flyback from the coil seems to be pos according to its direction through the diode, high voltage.

A coil pulsed with a neg current gives us back a pos polarity,

Will a coil pulsed the pos current gives us back a neg polarity,

Consider

[BroMikey]

Great Animation

The flyback from the coil seems to be pos according to its direction through the diode, high voltage.

A coil pulsed with a neg current gives us back a pos polarity,

Will a coil pulsed the pos current gives us back a neg polarity,

Consider

Hello Dave

I need more words from all of the guys here and you Dave to get me up to speed, but I will say this right off the top.

It seems like to have right there must be a left and to have a positive you will always have a negative.


It is very simple to me but maybe you had some other ideas in mind?

Either way I like the way you can put all of this into a picture.

Mike

[BroMikey]

New Block Diagram

Hello Cap Dump enthusiasts.

Here is the direction I am going building a capacitor discharging unit for zapping batteries. First of all I need to point out the main important thing about this diagram and that is the MOSFET NUMBER.

IRFP460

If we are going to follow just anyone around the web who "SAYS" that they now have a working example of a cap dump then let them demonstrate it, not just pass around diagrams that might work.

You will see circuits that promote the use of a IRFP250 for cap pulsing 36vdc battery banks and this is a poor choice for a MOSFET.

Why? And once again the "WHY" relates to the circuits durability and thus it's longevity. The MOSFET is no different than any other part in the industry having a maximum voltage rating and therefore common sense designs need to reflect intelligence.

Anyone following the battery pulsing/pump topology set forth by John Bedini must take into consideration what John has said. First off John and other men in the alternative energy field tell you that their circuits are not designed like conventional ones.

bye the way John Bedini made a statement in one of his videos that his work with cap dumps had nothing to do with what circuits were floating around the web and I now can see why he made this statement.

Lots of folks make diagrams of dumps that are not yet functioning in the practical world and in most cases have flaws to say the very least.

The first circuitry difference is that today's engineer is trained to snub out the ringing in the circuit and the alternative boys state that their circuits do not do that.

The Mosfet is said to be able to operate within 10 percent of it's peak ratings. So according to this a mosfet that have a peak rating of 200 volts can run all day long at 180vdc and as long as there are no other parts such as resistors, diodes, caps deviating from their values the fet will not go above 180vdc, maybe.

However this may be fine for a plastic toy robot, running the upper limits of a Mosfet is not best.

Here is a more sensible design for running a voltage of 100vdc.

The IRFP460 has a decent amp handling capacity yet has a voltage limit that will handle inductive kick backs. This has been found out the hard way with my circuits going up in smoke.

If it works don't fix it! right? Well that is right and I am throwing all of my IRFP250's back in the drawer for lower voltage projects, after all they are good parts when used the right way.

The circuit that is underway.

Tl594Dump.jpg

Like Dave is showing us all here in his animations that the coil kicks hard and a higher voltage type mosfet must be selected for pulsing 100vdc.

Our Computer PC power supplies use this part for pulsing 100vdc through a pass transformer so all I did is to look inside of a commercially produced product that is virtually indestructible to find commonly used design practices.

I don't care what the rating says, I am looking at what the industry does, not what it says. Don't do as I say do as I do or something like that.

See my hand? See my other Hand? See my data sheet and see how I build it?

Yeah the results are that the men inside who are in control of huge electronic companies follow the same rules as they always have and not the max ratings.

Otherwise they will be getting their products returned to the factory and we can't have that.

The general "RULE OF THUMB" or the "GOLDEN RULE" for any design criteria is that the parts Max rating is is multiplied by .7 and depending on who you talk to is 66 percent all of the way up to 75 percent so you get the idea.

Therefore if a Mosfet has a Max voltage rating of 200vdc and we multiply times .7 this is 70 percent and this equals= 140vdc.

Now we have the Mosfets upper voltage rating for building a circuit and in our case if we pulse that mosfet at 100vdc and the inductive kick comes back at three times that our part will soon be burnt completely out.

This is exactly what happened to me all this month long. I used 6 fet's in my line up as I built costume modules onto sinks.

As long as I stayed down to 40-45vdc as the pulsed voltage my dump would run fine for days.

The IRFP460's are in the mail and should show better results than I am getting.

2 days to a week for a set of brand new fet's is unacceptable.

I have to show you my homemade heat sink soon

Mike

[BroMikey]

Heat Sink Build

Here are the pictures of my new heat sink where 12 IRFP460 mosfets place 3 per side.

BroMikey's Science Projects

The fan is a 115vac ball bearing unit. Unlike the pc fan that works on dc the ac fan starts up very slowly and runs quiet for 5 times the air of the inexpensive PC fan.

The sink with the 6 patches of grease with bolts shown is what I originally had using a cheap pc fan just kind of blowing it across the best way possible.

Now the the square unit the air is forced through it like a duct work much more efficiently. The square sink is built from what is shown in the pictures using those 2 short fined sinks then shims to hold 1/16th" plate bolting one sink to the other.

This sink is pounded together very tightly before bolts are used to hold it in place. I am well pleased with it's tightness for a homemade design. The reason it is so tight is that the thin shims are tapered in wedge form and tapped in.

The top and bottom are bolted plates all aluminum build from stuff I had around the shop.

Mike

[BroMikey]

Hello Mario

Hi Mike,

If you follow the SOA curve of your devices you should not burn them.

I already wrote this, but if you use an opto the best rise/fall times you will be able to see on your Fets is 4-5 microseconds (not nano). It's simply not possible to go faster because it's the limit of your opto (h11d1).
Only using a driver you will be able to switch faster. So I don't know how you're able to see nanosecond switching if you're using an opto.

One reason for toasting fets can also be this:

When you turn the dump OFF very sharply (talking nanoseconds) and you are not dumping down to the battery voltage (even just 20 or 30V above the battery) you will get a negative spike that can be even a few hundred volts in amplitude. It's like your battery is behaving like a coil, you pulse it, and when you let go you get the flyback spike. This is why it's important to watch the dump pulse on a scope and learn all about it while you change parameters and see what happens.

regards,
Mario

Yes Mario I checked these rise times out as you suggest. The H11DX has a 2.5us rise so I am learning and trying to understand negative times as well as positive times. So far no one has answered any of my questions other than you and a few others.

I stated the rise times positive and negative have occurred with very small adjustment on the dial so who knows. Not me that is for sure.


I read some things and I see it is possible. The duty is throwing readings into the negative and giving faster rise times than 10ms. 10-20ms is showing up as well as I adjust. I noticed I had a bad scratch on my wiper on my 10 turn pot and I think this is throwing me off.

Also I read that the new opto's are faster now and I just bought them. I guess this opto is a 2.5us one.

Also I am reading the wave with a scope at the switch not the opto so when the opto fires the large transistor maybe it amplifies the speed of the signal?

The opto is connected to a pretty powerful transistor and that transistor fires the Mosfet. The Opto does not directly fire the Mosfet.


Is it possible that the transistor is firing at a faster rise time? You see as long as the opto fires the transistor fast enough and hard enough maybe upon firing the transistor it is faster. The transistor is just a medium power switching transistor that I put into the circuit to see what would happen.

The opto is able to fire the the Mosfet without a transistor between them.

I have not thought about rise times long at all and am only guessing about almost everything.

I would like to know why positive and negative rise and fall numbers appear as I adjust my 555 timer connected to my opto connected to a pretty good size transistor.

Mike

[BroMikey]

Rise times and false ones

Here is a video where the scope reading for rise times are ????????? or the ????
question mark is on the end of a fictitious number.

How to make a rise-time measurement on an oscilloscope - YouTube

This is the first video I have every seen that discusses rise times.

So even a modern scope does not read these fast times well in all cases.

Mike (PS still studying)

[BroMikey]

Pulsing 100vdc+

Here is a typical example of a commercially grown inverter board that drives a 115vdc 3 phase induction motor. I have lots of these things.

The diagrams show control board, motor and data sheet for the transistors with some ratings.

The whole point is that to pulse 100vdc a 600vdc max rated part is selected so anyone pulse charging a 36vdc battery should never use a 200v device.



This only one of many versions



This motor is used for most and a 14 amp part at 600vdc usually 5 or 6 devices to handle 800watts.

600vDevice.JPG

This is 10 years after Maytag went belly up and inverter boards are a dime a dozen. You can get one for $20 now used and these newer boards use common sense design topology, not some 10 percent of the max rating fly by night get rich scheme.

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

[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]

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]

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

[Mario]

Hi Mike,

someone correct me if I'm wrong, but as far as I know anything between the ON and OFF state of a mosfet means resistance thus heat. The faster you turn on and off the better for the mosfet. That being said keep in mind the back spike at turn off that can blow your fet, this depends solely on how much higher the cap voltage is with respect to battery voltage at turn OFF and how fast you turn off.
Talking about the battery, the more abrupt the pulse you send to it the better the "radiant" effect which desulphates and makes your battery last longer, not only its life but also the electric charge stored in it after charging it, if you don't wait too long before using it. The slower you turn on and off the more your square pulse starts to look like a round bump… not what you want.

regards,
Mario

[BroMikey]

Better all around

Hi Mike,

someone correct me if I'm wrong, but as far as I know anything between the ON and OFF state of a mosfet means resistance thus heat. The faster you turn on and off the better for the mosfet. That being said keep in mind the back spike at turn off that can blow your fet, this depends solely on how much higher the cap voltage is with respect to battery voltage at turn OFF and how fast you turn off.
Talking about the battery, the more abrupt the pulse you send to it the better the "radiant" effect which desulphates and makes your battery last longer, not only its life but also the electric charge stored in it after charging it, if you don't wait too long before using it. The slower you turn on and off the more your square pulse starts to look like a round bump… not what you want.

regards,
Mario

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

[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