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Solid States Devices => solid state devices => Topic started by: SeaMonkey on March 12, 2014, 05:38:02 AM

Title: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 12, 2014, 05:38:02 AM
BroMikey has built a CapDump Circuit (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit.html#post251979) which is in need of
some "fine tuning" to get it working efficiently.  He's
begun a thread discussion at the "other forum" explaining
his problems and his thoughts on resolving them.

If anyone here is able to enter discussion at the "other
forum" perhaps you'd consider inviting BroMikey to come
over here to get some real top notch assistance.

The problems he's experiencing are very common among
experimenters who've not yet got up to speed on the
"care and feeding of MOSFETs" and how to make them
switch capacitive discharge currents safely and efficiently.

Many thanks to any who provide technical assistance.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on March 12, 2014, 11:22:44 AM
BroMikey has built a CapDump Circuit (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit.html#post251979) which is in need of
some "fine tuning" to get it working efficiently.  He's
begun a thread discussion at the "other forum" explaining
his problems and his thoughts on resolving them.

If anyone here is able to enter discussion at the "other
forum" perhaps you'd consider inviting BroMikey to come
over here to get some real top notch assistance.

The problems he's experiencing are very common among
experimenters who've not yet got up to speed on the
"care and feeding of MOSFETs" and how to make them
switch capacitive discharge currents safely and efficiently.

Many thanks to any who provide technical assistance.
Any capacitor to capacitor charge shuttling circuit will suffer losses for several reasons.  The one that you cannot avoid without using a resonant topology is the N*(X/N)2 problem.  That problem basically says that you don't want much change in voltage between the two voltages in the shuttle.

Efficiency versus low side voltage / high side voltage at start of transfer for equal value capacitors:

0%  50% efficient
50% 90% efficient
80% 99% efficient
90% 99.7% efficient

So, keep the voltage above 80% on the low voltage side.  The other trick is to limit the surge current.  You can keep the MOSFETs cool by switching them reasonably fast and using an external impedance.  If for example you use an inductor, then you can realize a resonant transfer (this was the basis of the original now expired Vicor patents) and reduce the loss.  If pick a resistor that sets a time constant about 1/7th of the switching interval but that is significantly larger than the MOSFET resistance then it will absorb most of the energy that must be dissipated.  The current load that you can impose on the circuit is going to be limited by the switching frequency and the size of the caps, and the loss you are willing to suffer.  Or you can get clever and pick a piece of magnetics that will limit the initial current surge before saturating.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 13, 2014, 04:58:41 AM
Aye, the capacitor discharge surge current can have
explosive power and it may be necessary in some
applications to limit the surge to a safe value in order
to protect the switching MOSFETs.

The capacitive discharge surge rises near instantaneously
to a peak which can be hundreds to thousands of Amperes.
This is why Tesla loved capacitors and disruptive discharge;
it enabled him to produce very brief pulses of incredibly
great "horsepower."

It is essential when using semiconductor switches for this
purpose to turn them fully "ON" in the shortest possible time.
The proven most reliable way to do this is to use a MOSFET
Driver Chip capable of providing the necessary Gate Charge
Current located as close as is practicable to the MOSFET it is
driving.  Where a bank of parallel connected MOSFETs are used
which are each some distance from their adjacent MOSFET, it
is best to place a Driver Chip at each individual MOSFET.  The
logic signal input to the driver chips which controls their ON
and OFF timing may by applied from a single chip or pulse
source.

If a resistor is used between the output of the MOSFET Driver
Chip and the MOSFET Gate, it should not be too large.  In most
cases less than 10 Ohms.  This resistor is ordinarily used only
when switching the MOSFET at high frequencies in order to
relieve the Gate Driver Chip of excessive power dissipation
and excessive heating.  The Gate Drive Current at high frequencies
can be surprisingly high.

I've not yet seen the schematic diagrams BroMikey has made
up of his circuitry.  It would be appreciated if someone were
able to post them here for all to see and evaluate.

Commercial capacitive discharge welding circuits often use
a Silicon Controlled Rectifier (SCR) as the switching device.
The SCR is much easier to drive than a MOSFET and some are
able to switch thousands of Amperes in very short pulses.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on March 13, 2014, 05:20:25 AM
Yes, and no.  There are a couple of considerations:  An unintentional resonant circuit will cause current to pass back and forth between the capacitors multiple times, subjecting the MOSFETs to extra heating.  You want to avoid that.  This is where either turning the MOSFETs on in a controlled manner can actually reduce total heating by preventing the circuit from passing current between the capacitors over multiple oscillations.  The right amount of resistance either effected through the MOSFETs or applied externally can prevent a lot of loss.

An intentionally designed resonant circuit needs to have a mechanism to cut the current off when the capacitor voltages first match.  In that case you want a driver that can turn the MOSFETs off very fast.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 13, 2014, 05:44:07 AM
You may have a point MarkE.  I'm not yet clear on how
BroMikey intends to make use of his Capacitor Dump
Circuit. Judging from the size of his capacitor bank and
the layout of his switching circuit from photos he's
posted at the "other forum" it appears that it is
probably for very low to low frequency pulsing.  It rather
reminds me of the 30 Volt banks which were/are part of
impulse spot welding devices made for joining small parts
with a single pulse.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on March 13, 2014, 02:05:54 PM
It might be nice to see a schematic of the BroMikey circuit you are discussing. That other forum won't show you anything unless you are logged in.

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: ramset on March 13, 2014, 02:20:16 PM
 
I did post an invite at Energetic!
 
 thx
Chet
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: totoalas on March 13, 2014, 02:31:35 PM
bro mickey latest ckt ???
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on March 13, 2014, 04:19:50 PM
Aside from melting MOSFETs and damaging the battery plates, what is this circuit supposed to do?
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: totoalas on March 13, 2014, 04:33:10 PM
quote from Bro Mickey
I failed to include other info such as 80,000 uf 250vdc caps charging up to 90vdc.

Also the circuit that controls dump down voltage needed more resistance in the bases at 16K each. Just finished testing this. What happened was this is my first time using mosfet's for a dump so large and I trusted others who told me 200 ohms.

When I decided that the diagram I had was wrong my fets were toast so I started with 20k and nothing got through then 10k and 6k worked and 16k worked the best so my other pot control works with it well.

Another aspect of the dump is............ when i first hook the batteries to the dump they charge up the cap bank backwards through the fets I think, maybe this is smoking my junctions.

Again when I hook the 36vdc charge bank up to the dump with empty caps the power some how back tracks and I think to fast and this maybe damaging things.

So I thought like car audio caps maybe I better have those caps charged up first or think up some other protection. Who knows maybe I had 1 or 2 trashed fet's by then. I am in a whirlwind of study. Gotta think back and keep trying.

These are my first conclusions and will grow in the process of failures.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: totoalas on March 13, 2014, 04:35:12 PM
Another quote from Bro Mickey
I charged up my 120,000 uF bank just for fun to 65-70vdc and pulsed that through one big mosfet to a battery and that thing only worked once.

Maybe I will end up will 12 instead of 6 AAA?

But 1 or two? it's little legs just can't carry it.

My cap bank is set to deliver massive amounts of inrush to the battery.

By the way I did go down to 10,000 ohms of resistance on the base to get a full On so as to dump the entire load but that fet gave up the Ghost.

Just had to see. That pulse also burnt a tooth off of my gator clip so maybe the shorting out added resistance smoked the fet I do not know these things.

But one thing is sure the Wiley will always be my friend forever after that stunt.(http://www.energeticforum.com/images/smilies/rofl.gif)  Yes big big inrush amps enough to blow the sulfation right of a huge battery plate.

I am going to pick up some 500 ah 4vdc cells in a few hours.

So I need this thing working come hell or high water.

Yeah 10k on the base gave me a "FULL ON" condition and it smoked that fet in a New York mil second.

Mike
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on March 13, 2014, 04:38:51 PM
quote from Bro Mickey
I failed to include other info such as 80,000 uf 250vdc caps charging up to 90vdc.

Also the circuit that controls dump down voltage needed more resistance in the bases at 16K each. Just finished testing this. What happened was this is my first time using mosfet's for a dump so large and I trusted others who told me 200 ohms.

When I decided that the diagram I had was wrong my fets were toast so I started with 20k and nothing got through then 10k and 6k worked and 16k worked the best so my other pot control works with it well.

Another aspect of the dump is............ when i first hook the batteries to the dump they charge up the cap bank backwards through the fets I think, maybe this is smoking my junctions.

Again when I hook the 36vdc charge bank up to the dump with empty caps the power some how back tracks and I think to fast and this maybe damaging things.

So I thought like car audio caps maybe I better have those caps charged up first or think up some other protection. Who knows maybe I had 1 or 2 trashed fet's by then. I am in a whirlwind of study. Gotta think back and keep trying.

These are my first conclusions and will grow in the process of failures.
What does he hope to get from this combination MOSFET and battery eradicator?  Depending on how many pulses his MOSFETs survive, he is going to drive big pits into his battery plates.  He may also induce a hydrogen explosion in the batteries.  Lead acid batteries make a big mess when they explode.  Flying H2SO4 and burning metal are not the kind of stuff that you want to find yourself dodging.  I hope he is keeping all of this inside an explosion proof enclosure.

Charging a big capacitor bank to two or more times the battery voltage means that he is going to through a lot of energy away in the wiring and the MOSFETs.  A little work with Ohm's Law will determine a more appropriate voltage for the capacitors.  I don't care what he does with his MOSFET drive, the combination of a fat capacitor bank charged to 30V or more above his batteries is going to smoke the transistors.  That's about his only protection against dumping enough energy into the battery to create an explosion hazard.

There are lots of good pulse circuit based battery chargers that desulfanate out there.  He really should take a step back and reconsider the wisdom of the fire that he is literally playing with.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Hoppy on March 13, 2014, 05:03:37 PM

There are lots of good pulse circuit based battery chargers that desulfanate out there.  He really should take a step back and reconsider the wisdom of the fire that he is literally playing with.

Looks like he's doing a an ultra Berdini cap dump!!  :o
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: wattsup on March 13, 2014, 07:01:46 PM
@totoalas

hehehehehehehehehehehehehe. Man you iz a crazy bugger.

I think you will have to invent a new mosfet called Samurai Battery Pulsing Mosfets. You have to take a course in Harakiri first to get the full impact of a one shot pulse. hehehe

Pulsing is a bitch.

wattsup

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 13, 2014, 07:36:54 PM
Quote from: RamSet
I did post an invite at Energetic!
 
 thx
Chet

Thanks for doing that!

Totoalas,

Thanks for posting the diagrams - they're
very helpful.

In order to charge/desulfate a 36 Volt battery
bank as BroMikey hopes he'll need to add some
additional devices to his circuitry.  Gate Driver
Chips will be needed as well as a precise Pulse
Generator circuit (a 555 may do the job) which
produces a driving pulse of not more than 100
microSeconds.  Applying very short pulses to
the battery bank may result in a low enough
average power to avoid destroying the MOSFET
switches.

Caution is certainly necessary as a capacitor bank
charged to 90 or more volts is lethal.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on March 13, 2014, 07:43:41 PM
Ditch the mosfets and use a mechanical switch like a beefy double-throw relay or a solenoid-driven contactor. You can keep the contacts from welding shut by using the right capacitor across the contacts. Trigger the relay with a single mosfet driven by the Wiley Coyote control circuit. The relay's NC contacts can control the cap charging before the dump, then when you fire the relay the NO contacts close and dump the cap charge into the battery.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 14, 2014, 04:25:47 AM
Aye, the old fashioned approach with electro-mechanical
heavy duty relays is always good.  An automotive starter
relay or starter solenoid (http://www.ebay.com/sch/items/?_nkw=BWD+Automotive+R6242+Starter+Relay&_sacat=&_ex_kw=&_mPrRngCbx=1&_udlo=&_udhi=&_sop=12&_fpos=&_fspt=1&_sadis=&LH_CAds=) relay may be able to handle the
job with ease.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Hoppy on March 14, 2014, 08:42:40 AM
Ditch the mosfets and use a mechanical switch like a beefy double-throw relay or a solenoid-driven contactor. You can keep the contacts from welding shut by using the right capacitor across the contacts. Trigger the relay with a single mosfet driven by the Wiley Coyote control circuit. The relay's NC contacts can control the cap charging before the dump, then when you fire the relay the NO contacts close and dump the cap charge into the battery.

Agreed. I have in the past used an old multi-pole AC contactor and re-wound the coil for DC operation.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on March 14, 2014, 01:53:02 PM
I came to the conclusion that without some way to have the setup turn itself off I would need to keep checking it. So I went to a very simple picaxe setup which could sense the input and battery voltage. I also agree with others that say to recondition a battery they should be done separately. They can be better assessed individually as well. The circuit attached below is one I began with that I tested with a 17 volt input from a wall transformer and amateur code, I think I drew it correctly. I then used it with some different code and a solar input. I coded it to sense the battery voltage between pulses. I do realize I'm dumping through a diode but it's a good one and I needed it to sense the battery voltage. I modified it and built another circuit and wrote new code for a dual coil boost converter

The solar circuit is still on a solderless board  ;D but I'm not using it for a while anyway.

Anyway the basic switching setup with the mosfets is very sharp it makes the wires ping real good and I can pick up the ringing in the wires to the battery with another coil connected to my scope 4 meters away. I think the pinging affects me adversely, needs shielding I think, sounds nasty on the radio. Boost converter has paralleled smoothing caps so it doesn't have that issue. It's good to be able to plug it into the laptop and change the code to try different stuff. No need for the 12 volt regulator if a 12 volt battery is used for the supply. It can be coded to stop when the supply goes too low as well.

I don't think it necessary to use so much capacitance and voltage to dump to recondition a battery, it takes time though, a battery can't be desulfated overnight if it's sad to begin with. Slow and easy wins the race I think. I think proper discharging of the battery is important, placing a good load on a battery after it holds over 12 and a bit volts to discharge it with appropriate amp draw for the battery does wonders.

I also fear a battery explosion if too much voltage is used, especially if the battery is suspect in condition.

Cheers
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: totoalas on March 14, 2014, 02:07:31 PM
Patrick's comparator  ckt  as discussed in energyscience forum  ultimate cap dump
And Peter lindermans interview by Aaron  talks about solartracker 5
Radiant or inductive charging was changed to capaci tive charger  with 15.2 v float charge
Using dc linear amplifier desi .gn

Opting to use scr   maybe the future 8)



Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on March 14, 2014, 03:49:43 PM
I came to the conclusion that without some way to have the setup turn itself off I would need to keep checking it. So I went to a very simple picaxe setup which could sense the input and battery voltage. I also agree with others that say to recondition a battery they should be done separately. They can be better assessed individually as well. The circuit attached below is one I began with that I tested with a 17 volt input from a wall transformer and amateur code, I think I drew it correctly. I then used it with some different code and a solar input. I coded it to sense the battery voltage between pulses. I do realize I'm dumping through a diode but it's a good one and I needed it to sense the battery voltage. I modified it and built another circuit and wrote new code for a dual coil boost converter

The solar circuit is still on a solderless board  ;D but I'm not using it for a while anyway.

Anyway the basic switching setup with the mosfets is very sharp it makes the wires ping real good and I can pick up the ringing in the wires to the battery with another coil connected to my scope 4 meters away. I think the pinging affects me adversely, needs shielding I think, sounds nasty on the radio. Boost converter has paralleled smoothing caps so it doesn't have that issue. It's good to be able to plug it into the laptop and change the code to try different stuff. No need for the 12 volt regulator if a 12 volt battery is used for the supply. It can be coded to stop when the supply goes too low as well.

I don't think it necessary to use so much capacitance and voltage to dump to recondition a battery, it takes time though, a battery can't be desulfated overnight if it's sad to begin with. Slow and easy wins the race I think. I think proper discharging of the battery is important, placing a good load on a battery after it holds over 12 and a bit volts to discharge it with appropriate amp draw for the battery does wonders.

I also fear a battery explosion if too much voltage is used, especially if the battery is suspect in condition.

Cheers
The input side negative rail should be tied to your circuit common.  Maybe that's just an oversight in the schematic. 

When playing with batteries:  Always have a failsafe that can cut off supply current.  Don't apply voltages way above the current cell voltage.  If you want to knock the sulfur off use current pulses of moderate value.  Lead acid batteries also respond better if you charge, let them rest or even discharge slightly, and then charge some more.  Finally, temperature monitoring and enclosing in an explosion proof vessel are both good ideas.  Take a hint from Boeing with their Li-ion battery problems on the 787.  A case that can safely vent gas pressure without spilling toxic material into places where people are is a very prudent idea.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on March 14, 2014, 06:41:41 PM
The MJL21194 has a peak collector current of only 30 amps. Good luck with that, switching a big cap into a low-impedance load.

This would be a good place to put a cheap high-current mosfet instead of the big expensive BJT.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on March 14, 2014, 08:10:16 PM
I used a pair of IRL3705 mosfets @ 89 cents each, but IRF1010 would be better maybe for the solar setup same price, the switchboard is on a PCB all soldered up, it's just the electronics not permanent yet. I used what I had on hand for the boost converter IRFZ48 @ 74 cents each.

From here. Takes a while to arrive, but cheap.
http://www.futurlec.com.au/test13.jsp?category=TRANSMOSFET&category_title=Mosfet%20Transistors&main_menu=TRANSISTOR&sub_menu=TRANSMOSFET

Cheers
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on March 16, 2014, 12:58:21 AM
BroMikey has made a video (http://www.youtube.com/watch?v=QaOGgzp5EtE) showing how he intends
to use his Capacitor Dump Circuit as well as the
experimentation he's done with pulsing and
lead-acid batteries.

He's made considerable progress in his understanding
of certain basics but probably isn't yet ready for
in-depth technical discussion regarding MOSFETs and
how to best drive them as efficient switching devices.

Ammonium Alum as an additive to battery electrolyte
should show some benefit, similar to what the addition
of Magnesium Sulfate does;  but the best technique for
enhancing the longevity of the lead-acid battery is well
controlled pulsing to both charge and desulfate.  The
pulse width for the charging phase can be quite long.
Once the battery is nearly fully charged then the pulse
width should be made very narrow (not more than 50
microSeconds) to top it off and complete the desulfation.

FarmHands's micro controlled solar system would be
capable of handling that sort of charging algorithm.



Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on May 08, 2014, 09:16:20 AM
BroMikey continues to work with and improve
his CapDump Circuit.  He's asked a question (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit-3.html#post255374) but
hasn't yet received a response.

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.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on May 08, 2014, 10:16:51 PM
SeaMonkey, I quoted your posting over to EF and rambled on a bit myself to try to help a bit.

..

Oh I worked out there is a function to copy the code to a forum,  :-[ I had trouble trying to post code before.

Anyway just to show how dodgy my code writing ability is here is the code I developed to run the solar setup I posted above.

There is likely a lot of stuff that is redundant and others may not be able to understand it together with the drawing because there are no labels ect. in the code. To understand the code people would need to know the pinout and stuff for the 08M2 picaxe. Or look it up.  :D

..

main:
pause 1
readadc C.1,b1
if b1 => 152 then goto char
if b1 > 20 then goto boost
if b1 < 20 then goto humm
wait 1
goto main

humm:
do
low 2
pause 100
readadc C.1,b1
if b1 > 125 then low 2 goto boost endif
readadc C.4,b4
if b4 > 173 then pulsout 0,5 endif
if b4 > 173 then pulsout 0,5 endif
pause 100
loop

boost:
do
readadc C.1,b1
if b1 < 95 then low 2 pwmout 2, off goto humm endif
if b1 => 139 then low 2 pwmout 2, off goto char endif
if b1 < 130 then pwmout 2, 49, 50 endif
if b1 => 130 then pwmout 2, 49, 60 endif
readadc C.4,b4
if b4 => 149 then low 2 pulsout 0,3 pauseus 1 endif
if b4 => 150 then low 2 pulsout 0,3 pauseus 1 endif
if b4 => 151 then low 2 pulsout 0,4 pauseus 1 endif
if b4 => 152 then low 2 pulsout 0,4 pauseus 1 endif
if b4 => 153 then low 2 pulsout 0,4 pauseus 1 endif
if b4 => 154 then low 2 pulsout 0,4 pauseus 1 endif
inc b9
if b9 = 250 and b4 => 162 then low 2 high 0 readadc C.4,b5 low 0 let b9 = 0
elseif b9 = 250 and b4 < 162 then let b9 = 0 goto boost endif
if b5 => 143 then low 2 pwmout 2, off low 0 goto float endif
loop

char:
do
inc b9
readadc C.1,b1
if b1 < 138 then low 0 goto boost endif
if b9 = 252 and b1 => 140 then high 0 pauseus 1 readadc C.4,b5 low 0 let b9 = 0
elseif b9 = 252 and b1 < 140 then let b9 = 0 endif
if b5 => 140 then low 2 low 0 goto float endif
if b1 => 144 then high 0 pauseus 160 low 0 pauseus 100 goto char endif
if b1 => 143 then high 0 pauseus 140 low 0 pauseus 120 goto char endif
if b1 => 142 then high 0 pauseus 100 low 0 pauseus 180 goto char endif
if b1 => 141 then high 0 pauseus 60 low 0 pauseus 220 goto char endif
if b1 => 140 then high 0 pauseus 15 low 0 pauseus 285 goto char endif
if b1 => 139 then high 0 pauseus 4 low 0 pauseus 298 endif
loop
 
float:
do
pause 50
high 0 pauseus 1 readadc C.4,b5 low 0
pause 50
if b1 > 148 and b5 < 142 then pulsout 0,3 pauseus 2 endif
if b1 > 148 and b5 < 142 then pulsout 0,3 pauseus 2 endif
if b1 > 148 and b5 < 142 then pulsout 0,3 pauseus 2 endif
if b1 > 148 and b5 < 142 then pulsout 0,3 pauseus 2 endif
readadc C.1,b1
if b1 < 115 then goto humm
if b5 < 138 then goto char
loop

..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on May 09, 2014, 04:14:55 AM
Writing "Code" for a microprocessor or a
microcontroller is indeed a learned skill
and it can be daunting in the beginning.

If the Code fits into the available system
memory and does what it is intended to
to then it is Good Code.

If the initial effort is tightened up a bit
by modifying the algorithm and using
instructions which are more economical
of code space then it becomes Elegant
Code.

In the old days it was often necessary to
reduce the Code in a program to the
barest minimum because of ROM and RAM
limitations so some programmers got really
good at finding the most economical way to
accomplish almost any task.  They were
the ones who got the Big Bux.

Your Code is an excellent example of how
a fairly complex job is done;  the thought
processes which enter into the solution and
the sequence of events necessary to make
things happen when they should.

Any Code that does what it is supposed to do
is Good Code...
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MileHigh on May 09, 2014, 05:15:47 AM
I can do 8086 and 6502 assembler!  lol

I _hate_ the 80X86 instruction set.  The 680X0 lost out, it's a shame.

So Farmhand, is it you that wrote the nasty script that's crashing on OU recently?  lol
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on May 09, 2014, 05:37:22 AM
 ??? Hilarious, it would take me years to even entertain the thought of being able to do such things. If anything I am a victim there as well. I must check for any developments over there. Might be something interesting.

To write the code above I had to refer to the picaxe pdf every time I needed to do something different and look for a way to do it. I just made the circuit with a pretty good idea of what the chip could do and then worked out the code later. Took a while, no interrupts used, still haven't worked that out yet. I've got Arduino now too but haven't even used it yet.

The 08M2 chip is good for beginners, it's small, cheap and can do basic stuff with simple code.
..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on May 09, 2014, 07:04:57 AM
Quote from: MilesHigher
The 680X0 lost out, it's a shame.

Aye, it did and I thought so too.

The Commodore Amiga and the Atari ST series
did mighty fine with it and were quite advanced
for their time.  Ah, those were the days!

Quote from: FarmHand
I quoted your posting over to EF and rambled on a bit myself to try to help a bit.

Your "ramblings" added a great deal to the discussion.
You did well.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on May 09, 2014, 10:24:43 PM
Going by the schematics on the previous page, Bromikey seems to be using a high side switch between the caps + and the battery +, he would be better served to use a low side switch between the battery negative and the cap negative. That would simplify the driving circuitry.

If he has the mosfet drain at battery voltage he will have problems without a working level shifting driver circuit or something. I'll ask him.

Cheers
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on May 10, 2014, 10:46:49 PM
I've just recently downloaded the newer manuals for the picaxe chips and it tells me now that the M2 chips can all run at the default clock speed of 4 Mhz or they can be clocked up to 8 -16 and 32 Mhz, the old manuals only stipulated that the M2 chips could be clocked to 8 Mhz. Theoretically the M2 chips at 4 Mhz clock speed can output a 500 Khz PWM signal,
but at 32 Mhz the theoretical PWM signal could be 4 Mhz. Not bad for a cheap 8 pin micro.

What I like about the smaller chips is the price, the small size and low power draw along with many of the functions of the larger chips. For more outputs and inputs the 14M2 seems good and I intend to use those more.

..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MarkE on May 11, 2014, 02:03:45 AM
I've just recently downloaded the newer manuals for the picaxe chips and it tells me now that the M2 chips can all run at the default clock speed of 4 Mhz or they can be clocked up to 8 -16 and 32 Mhz, the old manuals only stipulated that the M2 chips could be clocked to 8 Mhz. Theoretically the M2 chips at 4 Mhz clock speed can output a 500 Khz PWM signal,
but at 32 Mhz the theoretical PWM signal could be 4 Mhz. Not bad for a cheap 8 pin micro.

What I like about the smaller chips is the price, the small size and low power draw along with many of the functions of the larger chips. For more outputs and inputs the 14M2 seems good and I intend to use those more.

..
An alternative 8 pin part is the Atmel ATtiny85.  64MHz PWM oscillator, ~$1.00 each.  The core runs 8MHz, 8MIPs.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on May 11, 2014, 07:59:16 AM
Mark those chips look awesome, I scanned this document below and found a lot of interesting functions it can do. And the price is much better than picaxe, however. How long would it take me to learn how to write code for it. I'm a complete novice, the way I see it trying to learn how to write programs for picaxe is difficult enough, and I also want to learn how to use Arduino.

Is there a language I can use to program them all ?

It has some good PWM features.

http://www.atmel.com/images/atmel-2586-avr-8-bit-microcontroller-attiny25-attiny45-attiny85_datasheet.pdf 

..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 17, 2014, 08:18:02 AM
BroMikey's self-education project continues to reveal to him
interesting developments (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit-7.html#post257773) just when he thinks he's got it
figured out.  His education has progressed to the point
where he "knows enough to be dangerous."

Not meant to denigrate BroMikey or his endeavors but it is
a phase that all aspiring electronics technicians work through
as they grow in their understanding.

Six paralleled MOSFETs should be more than capable of handling
40 Ampere pulses, or even more, if properly driven and properly
protected from flyback pulses which are capable of destructive
avalanche of the MOSFET Body diode.

Hopefully BroMikey will either find the answers to his dilemma through
his own research efforts or a knowledgeable tech will provide him with
the elusive technical details he hasn't yet found.

It is possible in his case that his MOSFET gate driver chips aren't properly
positioned as close to the MOSFETs as possible and with sufficient capacitance
to properly drive the Gates.

It is also possible, and very likely the case, that the length of the cables from
his capacitor bank to his battery bank results in quite a lot of stray inductance.
At the instant pulsing current switches off a very substantial flyback pulse will
be generated which, although very brief, will take the MOSFET's into avalanche.
Since avalanche characteristics are quite different amongst the parallel connected
MOSFETs it is probable that one of them will serve as a current hog for the avalanche
current.  In time this will destroy the MOSFET and result in its failure much as has
been the case so far with his setup.

Thankfully, these problems are rather routine in high current switching systems
and the remedies are well established,  BroMikey will find success if he keeps
searching.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 17, 2014, 09:02:51 AM
Faugh. I looked at that post and I can see that BroMikey is terribly confused and is clearly doing something wrong.

The IRFP460 has Rds 0.27 ohms (when switched fully ON; higher if not), Id max 20 A reducing to 13 A at 100 degrees C, and 500 Vdss. Its max _power dissipation_ is 280 Watts when it's on a good heatsink.

He is thinking that 3 amps at 80 volts is getting close to the mosfet's limit! Because 3 x 80 is 240 Watts and the data sheet says 280 Watts at 25 C!!!
But this is derated 2.2 w/degree C, so at 110 C the power dissipation limit is actually 280 - (2.2 x 85) = only 93 Watts. Hence the need for cooling at high power levels.

But really, if the  mosfet is carrying 3 amps it is dissipating I2R or 3x3x0.27 = about 2 and a half Watts !!!! 6 amps boosts it up to nearly 10 Watts. The mosfet can easily handle this even if not on a heatsink or fancooled. You'd think he'd notice the room getting a bit warm, if his bank of mosfets was really dissipating nearly 3 kW.

Let's say the mosfet is carrying 20 amps.  How much power is it dissipating? 20 x 20 x 0.27 = 108 Watts, exceeding the max power limit at higher temperatures. How about that. It must be kept cool in order to operate at that power level. So again we begin to understand the relationship between mosfet power dissipation, the maximum rated limits of Id and Pd, and the need for proper cooling at high power levels.

But he's pulsing at 3 Hz with 250 ms ON time for a duty cycle of 75 percent, so that lowers the actual average power dissipation accordingly.

So if his mosfets are running hot and failing it most probably means he isn't switching them properly _and_ he is getting huge dissipation from avalanching on switch-off, not failing from carrying too much current per se. They are nowhere near their actual power handling capacity when properly switched.

Quote
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.
 
 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.

Insert facepalm here.



ETA: That "also passing voltage with it" phrase indicates to me that BroMikey's mental model of electricity is wrong, and he is misleading himself because of it.

Cure #1: put an ultrafast, high current diode reverse biased across each mosfet. MUR1560 for example, anode to Source and cathode to Drain. These diodes may also need to be heatsunk.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 17, 2014, 11:06:38 AM
Maybe if he is dumping enough capacitance charged to a high enough voltage into a battery he might be exceeding the maximum pulsed current rating for the mosfet, and with several in parallel one mosfet might be taking most of the abuse, as a cap discharge can produce a very high initial peak current.  :D That is why it's done, isn't it.

And coupled with poor switching and high "on"resistance then "Pop goes the mosfet".

He also mentioned at one stage he w is using quite long cables, like meters in length.

I've made a drawing for him with a store bought transformer run from the wall to give a 12 + 12 volt supply so he can rectify 12 volts for switching supply and 24 volts for charging the caps with a Large inductor between smoothing caps and dump caps to partially isolate the dump cap from the supply when dumping.  Maybe a MOT primary would work there, (just remove the secondary for safety XXX).

..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 17, 2014, 07:08:29 PM
Some reading material.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 17, 2014, 07:30:59 PM
Maybe if he is dumping enough capacitance charged to a high enough voltage into a battery he might be exceeding the maximum pulsed current rating for the mosfet, and with several in parallel one mosfet might be taking most of the abuse, as a cap discharge can produce a very high initial peak current.  :D That is why it's done, isn't it.

That's true. A capacitor discharge can produce very high currents, the more capacitance the more current ... into low impedance loads. The max pulsed current for the P460 is 80 amps and that's under pretty narrow pulse parameters. So if he's charging to 80 volts, then dumping the caps through a single mosfet due to poor paralleling, he needs at least one whole ohm of impedance in the circuit after the mosfet, to keep the max current below 80 amps.  R = V / I  so 80/80 = 1 ohm. Oh, wait, the mosfet itself has 0.27 ohms minimum resistance, so the rest of the circuit needs less than three quarters of an ohm impedance (resistance) to keep the maximum surge current below 80 amps. No matter the capacitance.

I'm still having my first coffee of the day, so please check my math and reasoning.

Dumping a cap through a mosfet into a load is a lot less problematic than charging an empty cap through a mosfet switch or crowbarring a cap bank with a mosfet. The empty cap looks like a dead short, so if the supply voltage is there, the surge current in the mosfet can be very high. But dumping a cap into a resistive or inductive load with a mosfet is much less problematic because the load impedance limits the surge current. I think.


Quote

And coupled with poor switching and high "on"resistance then "Pop goes the mosfet".

He also mentioned at one stage he w is using quite long cables, like meters in length.


Then he should put the diode I mentioned above, at the load end of the cables, and supplement with an additional similar diode right at the mosfet pins.

Quote
I've made a drawing for him with a store bought transformer run from the wall to give a 12 + 12 volt supply so he can rectify 12 volts for switching supply and 24 volts for charging the caps with a Large inductor between smoothing caps and dump caps to partially isolate the dump cap from the supply when dumping.  Maybe a MOT primary would work there, (just remove the secondary for safety XXX).

..

Is the complete actual circuit he is actually presently using right now, available for study? I'd like to take a look but I can't be arsed to sift through page after page of nonsense at EF.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Kator01 on June 17, 2014, 07:58:46 PM
Hello,

this subject has been covered by diifferent physicists starting with Heinrich´s first publication 1985, so I wonder why this topic is brought up anew again and again.

Here are some publications, starting with Heinrich´s work:

http://freenrg.info/CAPTRET/Entropy_Change_when_charging_a_cap.pdf (http://freenrg.info/CAPTRET/Entropy_Change_when_charging_a_cap.pdf)

http://xputers.informatik.uni-kl.de/conferences/patmos/patmos98/desoete.pdf (http://xputers.informatik.uni-kl.de/conferences/patmos/patmos98/desoete.pdf)

http://arxiv.org/pdf/1201.3890.pdf (http://arxiv.org/pdf/1201.3890.pdf)

Regards

Kator01

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 17, 2014, 09:36:54 PM
Aye, BroMikey still has a ways to go before he acquires full
and complete technical understanding of what he's up
against with his circuit.

Good education always seems to come with some sort of
pricetag - be it in dollars or burned out MOSFETs.  But the
rewards can be enormous if the "student" has the gumption
to stick with it until he is finally able to make it do what it is
supposed to do reliably and without fear of premature failure.

And know the reasons why...
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 18, 2014, 01:42:31 AM
Tinsel he is charging the capacitor bank from a series set of batteries to get the higher voltage "through a resistor" to limit the current when he discharges the capacitor, I explained how much power the resistor is dissipating when he does that, then he is dumping the huge cap bank through the paralleled mosfets to the batteries. I think he is using a large capacitance 10,000's of uf and charging the dump caps to more than double the battery voltage, maybe triple.

When we dump caps the caps end up not discharging to zero volts they end up at battery voltage, when the cap is first connected it charges to just under charge battery voltage.

I suggested he use a mosfet to isolate the supply from the load when dumping or use a series inductance coil to partially isolate the supply for at least part of the dump.

A better way would be to use a transformer to charge the caps. And prime the caps if the bank is high uF.

Or if using a series batt set to charge the bank he really needs to isolate the supply series string of batts from the batt he is dumping into.

What would be the peak current of 36 volts in a 200,000 uf cap dumped into a paralleled set of four 12 volt batteries in good condition ?

I haven't taken the time to verify what circuit he is using right now, I'm just going by his descriptions.

I haven't destroyed a mosfet for a long time now, I mustn't be trying hard enough.

..

Fairly sure a NC relay could be used to rout the transformer output through a resistor to initially "prime" the large cap bank, then when the caps are charged the relay would turn on to give a low resistance charge path from Xformer to caps..


..






Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 18, 2014, 04:02:48 AM
Quote
What would be the peak current of 36 volts in a 200,000 uf cap dumped into a paralleled set of four 12 volt batteries in good condition ?

The peak current depends on the total resistance of the circuit plus load. The capacitance _does not enter into it_.

The peak current into a _direct short_, when switched by the mosfet, is found by applying Ohm's Law: I = V / R. 
Since v = 36 volts and R = 0.27 ohms, the mosfet's minimum on-state resistance, the maximum current is just over 133 amps. Into a dead short, from whatever you are using that provides 36 volts, whether it be a capacitor of infinite capacity or a battery or a hydroelectric power plant.

For _how long_ can that peak current, or any current, be sustained? NOW the capacitance matters. Higher capacitance, more energy, more time to discharge it. As soon as the discharge from the cap begins, the voltage will begin to go down and the current will drop from its peak value, and as the voltage decays exponentially so does the current. More capacitance, longer time constant. More _voltage_ more peak current.

Now let's imagine a more realistic load impedance. Say it is one single ohm. Now solve I = V / R, and find that you can only push a bit over 28 amps through the circuit, no matter what the source is, no matter what the capacitance you are dumping is. That solution to Ohm's Law is the _maximum_ current that 36 volts will push through your circuit.

Now I don't know what other elements he has between the mosfet switch and the load, or what the equivalent internal resistance is of his battery banks, but I will bet that the total circuit resistance, even with all six mosfets properly paralleled, is more than 1.27 ohms. Which means that the _maximum pulse current_ from a 36 volt source will be less than 28 amps.

However in his post he says he's using 80 volts and is attaining 6 amps per mosfet, or 36 amps total. Again, solving Ohm's Law, we find that using those numbers at face value, R = V / I gives us a total circuit resistance of a little over 2.2 ohms.

So going back to the original question, if your capacitor of a million billion Farads is charged to 36 volts, what will be the peak current when it is discharged thru the mosfet (or thru a simple mechanical switch closure) into BroMikey's 2.2 ohm circuit? I = V / R = 36/2.2 = less than 17 amps. A single mosfet will work safely for a 36 volt supply, IF the backspike is handled properly.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 18, 2014, 05:35:59 AM
Yes I understand that the peak current is limited by the voltage / resistance. basic stuff I'm not sure exactly why I wrote the uF value  except to say it is a high uF bank of several paralleled capacitors, won't that affect the resistance of the current path ? And if the batteries were paralleled then less resistance as well. I understand that no matter what the capacity of the supply it is voltage and resistance that determine current in DC.

Anyway it seems the problem is improper switching like most cases and since I don't have the time to help him, Matt over at EF will have to continue to do it. See no one helps anyone over there and he has been invited over here so, it's up to him.

With so many mosfets in parallel they probably are not turning on properly, I had to explain to him that there is a high peak current in a coil discharge to a battery, he was led to believe there was none, and also that to drive a mosfet requires current when some nong posted that mosfets do not require current for switching. Meaning I had to try to explain displacement current to him.

With the mosfets not turning on properly he has no chance.

..

To put it very simply if he cannot do it with one mosfet he is doing it wrong. Not much point trying to help people that want to parallel up hand fulls of mosfets.  :) And he is charging the caps from a battery series set through a resistor. Wow.

..

The other thing I meant to mention was he may be exceeding the Gate to Source voltage limit. Gate abuse maybe.

..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 18, 2014, 07:23:28 AM
BroMikey is struggling with some internalized misconceptions (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit-7.html#post257822) and still
lacks full understanding of some critical details.  He's still in the embryonic
stages of his technical development.  Ways to go yet.

And yes, BroMikey you're reaching some of us.
 (http://www.energeticforum.com/renewable-energy/16696-cap-dump-circuit-7.html#post257826)
The good news is that we've all been there; it too will pass. Then the
real understanding will congeal with eye-opening results.

Don't stop the quest!  True understanding is built upon numerous
failures which are temporarily disappointing but serve to fuel the
fires of desire.  The desire to know with certainty.

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 18, 2014, 07:54:38 AM
It seems pretty clear from those posts that BroMikey already "knows" all he is ever going to know about mosfets and cap dump circuits.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 18, 2014, 08:37:09 AM
Aye, one could easily come to that conclusion after reading his
postings.  I suppose we shall see in the coming days, weeks and
months whether this Old Dog is up to learning some new tricks.

Being stuck inside the "box" puts a real damper on progress...

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 18, 2014, 02:03:51 PM
Well I decided I had some time so I set up a dump circuit using one mosfet from my LF power control board and dumped 26 volts into a 12 volt battery from a 45,000 uf cap as shown. The smoothing bank should have been at least three times larger.

I got about 13 amps peak current and the current sense resistor at 0.8 ohms got real hot but my mosfet stayed cool  8) to touch.

I'll put some shots here and the circuit for those who cannot log in over there.

Circuit
then applied voltage in blue and current in yellow across the 0.8 Ohms.

then The voltage on the two cap banks with the inductor between them

Second shot shows gentle waves but the first shot shows sudden violence.  ;D

Oh and a rise time shot. Slow mosfet.

The 14 Amp hour motorcycle battery I'm charging could do with the experience of some decent current it hasn't been used to start the bike for a long time.

Took out the 0.8 Ohm resistor and all is going well, mosfet cool. Battery voltage bouncing and increasing.  ;)
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 18, 2014, 06:41:34 PM
Very good FarmHand!  That is how it should be done.

The "charging choke" with diode isolation will accomplish
resonant charging to some extent.  No waste of energy.
(Well, perhaps a tiny bit - but not excessive as would be
the case with a resistor.)

What value of capacitor did you use across the Gate Driver
Chip?

Excellently documented by the way.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 18, 2014, 07:40:50 PM
Mm-hmmm.

The peak current shown is a bit over 13 amps, I estimated 13.7 or so. But the average current during the pulse seems to be about 3 or 4 amps, and taking the 33 percent duty cycle into account that means that the average power dissipation  I2R in the mosfet itself is ((4 amps)2 x 0.01 ohms) x 0.33 = a bit over 50 milliWatts. And since it's being switched cleanly by a good squarish pulse of 12 volts from the gate driver, it's not adding much switching loss to that. So no wonder it stays cool!

If you now make the capacitors bigger (more capacitance) and charge to the same voltage and use the same duty cycle, you will get higher average current (the exponential decay time constant will be longer) and you will get more energy transferred into the battery per pulse. The _peak_ current will still be the same.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: SeaMonkey on June 18, 2014, 07:54:06 PM
Excellent analysis and suggestion to sustain current flow
through the duration of the pulses.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 18, 2014, 10:11:46 PM
Well all I need to do is to program the picaxe chip to pulse with narrower pulses and faster and then I get a squarish current wave form if I go narrow enough. Then the capacitor is only partially discharged so current flows the whole time if the pulses are narrow enough.

Anyway I think bromikey was under the impression his caps were fully discharging, and he may have a slow turn off. The residual current flow I think is through the inductor anyway. If I was doing it my way I would use a smaller capacitor and pulse at some kHz. I think with his resistor there is always residual current flowing no matter how long his discharge time is, and if his mosfet is not turned off fast he will heat it up.

If I used smaller caps and faster narrower pulses then I would not need to worry about using an inductor even, I only did that to get the dump cap voltage down at the end of the dump. A MOT primary would work better with 250 mH inductance and thick wire.
A low loss current limiter for a moment.

SeaMonkey I have only 100 nF caps across my driver chips on that board, I need to add the 10 uF caps as well yet. The driver supply is regulated to 11.95 volts so the chips need more reserve energy.

The coil I used had way too much resistance and not enough inductance and the caps were too big to get a voltage rise from the resonant charging circuit. After an hour or so the coil was so hot I could not pick it up, I waited 30 minutes so I could pick it up and used it for a pocket warmer, it's a bit cold here now.

I charge my batteries with a 6 amp dual output solar system, I only pulse batteries to keep them in good condition or rejuvenate them. And never excessively. I treat them usually with only 1000 uF discharges from about 22 volts and at random frequency the cap discharges when the desired voltage is reached and pulses to keep 17-18 volts on the panels, max power voltage.

All my batteries are in good condition and are kept charged and used, with the exception of the motorcycle battery, it doesn't get much use, but I keep it charged.  Motorcycle batteries fail at the drop of a hat, they are too compact to be long lasting.

..

Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 19, 2014, 12:19:55 AM
Shortening the pulse will square off the top of the current trace all right... by preventing the capacitor from discharging. Don't forget that _energy_ is the time integral of power. So if you shorten the pulses, all else being equal, you will be delivering _less energy_ per pulse. Is there a tradeoff? More pulses per second, but less energy per pulse.... or a capacitor that isn't discharging as far so it takes less energy to recharge it back up....   There will be an optimum pulse width and frequency that transfers the most energy -- corresponding to the highest average power -- I think.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 19, 2014, 01:44:24 AM
Here's a couple more shots one at 400 Hz 10% duty and one at lower frequency, at 400 Hz it pulled the dump cap voltage down due to the MOT primary's 260 mH inductance. I should have tried 200 Hz, at 400 Hz it was pulling 90 Watts out of the wall without the CSR and driving the battery voltage up like mad but also warming up the mosfet just a bit, not hot just warm. At the lowest setting it pulls a fluctuating 20 to 35 Watts and makes the voltage bounce.

Haha at 400 Hz it punching rectangles of current into the battery at a rate of over 10 amps a shot for 260 uS.

I think rather than paralleling mosfets a better way might be to use ie. four mosfets switched in turn so that each one has one 1/4 of the total work to do. Time to cool.

..

Well I guess at 10 Amps @ 10% duty it is giving a 1 Amp charge to the battery.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MileHigh on June 19, 2014, 02:11:59 AM
Farmhand:

Assuming that you have complete control over the pulse of current into the battery, the next logical step is to use that to maximum advantage.  Without any direct experience myself, you can make a reasonable assumption that you get diminishing returns as you increase the amperage.  Eventually at some high current level the battery will act like 99% resistor, 1% recharging battery.  Also, presumably, standing and charging voltages well in excess of 12.6 volts are also not healthy for the battery.  It's because the EMF potentials set up by the molecular action are supposed to be at 12.6 volts (for the cells in series.)  So in my opinion, you get some kind of "brain fry" going on when the battery is at say 16 volts.  I am sure I have read in a few places how these excessive voltages do damage or reduce the life of the battery, etc.

I am not suggesting that you are doing any of these things, I am just pointing out the limits of going to extremes.

Anyway, the fun part would be to find the "sweet spot pulse regimen."

I am willing to get you that better battery chargers use a microcontroller to do something like this.  You can develop software to sense the battery's condition and adaptively charge it.  I remember reading the information about a pulsing battery charger from a Big Box store a few years ago and reading stuff like that.  I also read about a system that did the same for extracting power from solar panels.  Depending on the illumination level, the impedance match for extracting the maximum amount of power from the solar panel will change, and the microcontroller in the charger/interface to the solar panels would dynamically adapt.  I stumbled there because the Bedini "high tech" solar charger was out.

Finally, charging batteries or extracting the maximum amount of power from a solar panel is a perfect fit for for solving the problem with the application of "fuzzy logic" using a microcontroller.  So I bet you that there are fuzzy logic solutions out there but I doubt they use that term in the marketing.

MileHigh
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 19, 2014, 02:46:22 AM
OK with about 250 mH inductance in the coil and if I reduce the output caps to 15000 uF then I should get resonance at about 2.5 Hz.

So then I think I can switch at double that frequency to still almost double the voltage in the dump cap after switching.

And with the diode the voltage stays and no reversal so anything between 2 Hz and 5 or 6 Hz should work well with the charging circuit.

If so the 15,000 uF cap will end up with almost 50 volts on it. I'll try it out while I'm going, mosfets are only rated to 55 volts so I might lose it.

Ahh the joy.  :)
..
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 19, 2014, 03:19:16 AM
I only got a little tiny voltage rise. I backed off the input to take care, with more input voltage and more current caused the coil will work more because it will get more current.
Yellow is the dump cap voltage and blue the supply caps.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 19, 2014, 08:21:59 AM
I hear youse all, MileHigh, I already had one such setup dealing with solar input to a system that is often under what most charge controllers deal well with, it sensed the input voltage, the output cap dump voltage and the battery voltage when the mosfet was conducting with the same voltage divider that sensed the output dump cap voltage. It used a boost converter to boost the low input from the panels to 22 volts so as to apply some rejuvenating to the battery, and when the battery was charged it would go into float mode then kick back in when the batt voltage dropped. It is no use if the battery is badly sulfated though because it automatically goes into float mode if the voltage rises above 14.4 volts. I made it so it would float at 13.6 volts.

I'm only doing this for fun and to help BroMikey cast out the fallacies he hes been fed by "the crew" over there. One of the big problems is that the battery is drawing from the supply through his resistor, using a MOT primary I can dump 15 K uF in 40 mS and 350 mS between pulses to recharge the cap and get down to almost zero current flow, longer and the MOT primary starts to pass current directly from the supply to the battery, this is to be avoided.

The other way is to disconnect the  + rail of the supply from the dump section before dumping and I've already done that too.

Using a big low resistance coil and the right on time is simpler and less parts.

My coding is very basic self taught, I can only do so much without wasting too much time.

..

Now if it was me I would be inclined to go down to a 4000 uF dump capacitor and increase the frequency.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 19, 2014, 09:25:25 AM
SeaMonkey, Talking of driver capacitors, this board I made mainly for controlling relays and small motors ect. and for LF experiments for ease of power control. So I ran out of space for another capacitor on each driver chip so I might just use a 100 uF cap across all of them and I can fit a 10 uF cap across the two with PWM outputs. They all have a 100 nF across them. I've seen several combinations used but usually they all contain at least one ceramic cap. Why is that ?

I've got four mosfet switch outputs on the "B" output side of the 14M2 picaxe chip (two have pwm ability), on B.5 pin I use the analogue to digital converter to sense the variable voltage provided by a voltage divider which is a big 5 K pot, I use the pot to set the program into different "stages" manually which I can make to do whatever. On the input "C" side of the chip I have them set up to take inputs or be outputs to other boards.

I think I can have the board play a music tune when the battery is charged.  ;) I wonder what funky tunes are available.
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Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 19, 2014, 08:09:54 PM
SeaMonkey, Talking of driver capacitors, this board I made mainly for controlling relays and small motors ect. and for LF experiments for ease of power control. So I ran out of space for another capacitor on each driver chip so I might just use a 100 uF cap across all of them and I can fit a 10 uF cap across the two with PWM outputs. They all have a 100 nF across them. I've seen several combinations used but usually they all contain at least one ceramic cap. Why is that ?
The small ceramic cap right at the chip is "AC bypass" that keeps the chip from responding to noise on the supply feed and helps to prevent false triggering. This is just about universal, especially if supply leads are long. Put the bypass cap as close as possible to the chip itself.
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I've got four mosfet switch outputs on the "B" output side of the 14M2 picaxe chip (two have pwm ability), on B.5 pin I use the analogue to digital converter to sense the variable voltage provided by a voltage divider which is a big 5 K pot, I use the pot to set the program into different "stages" manually which I can make to do whatever. On the input "C" side of the chip I have them set up to take inputs or be outputs to other boards.
That is the same technique I use to control which subroutine is running in my NeoPixelRing demonstrator. I have eleven different independent program segments, each selectable by the 50 k 10-turn pot with turn-counting dial on the front panel. Select something between 100 and 200 on the knob for example and you get program segment 2, and while "2" is running I can even control a function by varying the pot within that range (one full turn of the 10-turn pot). Since the picaxe (or in my case Arduino Pro Mini) ADC input is sensing voltage and is a high impedance input, you can make the voltage divider pot just about any value, even 1 megohm. Making this voltage divider pot large will cut down on the overall current consumption. I use 50K because that's what I've got on hand.
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I think I can have the board play a music tune when the battery is charged.  ;) I wonder what funky tunes are available.


 

There are billions of bits of 8bit music out there. It takes a bit of fiddling to get accurate note values but sure, you can do that if you have the memory available once the "meat" of the program is in the chip. I don't know what is available for picaxe but for Arduino there are many many aftermarket "shields" that simply stack onto the main board, no soldering or wiring required, that will do all kinds of things. Music shields that incorporate microSD card slots are available that will play high-resolution music or any audio file you can put on an SD card.
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 20, 2014, 02:15:15 AM
Thanks Tinsel, I'm sure SeaMonkey has already told me why but I was likely in the land of pain and pills and forgot.  :-[ Thanks .

MileHigh, I also purchased a quite good 1/6 amp current pulse charger with a four stage charging algorithm. When the battery is first
connected and the unit turned on it checks for reverse polarity connection, Low voltage (short circuit) and open circuit in the battery.
The if the battery is real low it gives a 1 minute 1 amp charge and then analyzes what to do next, if the battery is ok but a bit sad
(sulfated) it gives the battery a "refresh" about 10 minutes (or however long it needs) of about 500 mA current which I think is HF small uF cap discharges.
When that is finished it goes to bulk charging (constant current) then it goes to Absorption (constant voltage) for a while then it floats the batteries at 13.6 volts.

It calls it's action in charging a Pulsing Current Pump.

Model is obsolete - MB-3624 - Power Tech Plus - but similar units of a later model are available.

It's a sealed unit and small and light, only drawback I had was a fuse in the output wire had a poor connection and made the wire hot. Other than that it works pretty good. But it doesn't go - tick....tick...tick....and it only has one button, grrrrr.

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Last night I used my cap pulser to charge the 14 Amp Hour motorcycle battery right up and to know when it's fully charged when charging it with LF pulses is not easy, when the battery is showing about 13.8 volts mostly but the pulses take the voltage over 14.6 then it's charged. The MC battery was making all kinds of funny belching, bubbling, fizzing and buzzing noises when it got towards being charged, I stated to get concerned when I heard the battery "buzz". This morning I connected it to the 70 Watt solar setup and it took good current for a brief moment but went directly to fully charged and floating.

The circuit was going tick...tick...tick... with the discharges and the battery every now and then went bzzzzzz, bloop,bloop, all the while making the sound of a freshly opened coke.  ;D


P.S. I gotta say that 2 Hz is the lowest frequency "resonant charging circuit" I have ever put together. Very low "Q" for sure. But it still works a bit.  8)
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Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MileHigh on June 20, 2014, 05:02:35 AM
Farmhand:

I am glad you are having fun.  When you program a micro, and especially when you program it in machine language, it's like you are a god.  No operating system, just the first bytes of code that you put into the memory location when the device comes out of reset.  You are probably aware of how in the 70s and early 80s programmers would squeeze their machine language code into 8192 bytes of memory.  They accomplished things that nowadays probably gobble up a few megabytes of space.

When Bedini released his solar-panel-based pulse battery charger, it started with the deke out about how they allegedly had to detune it so they wouldn't "get in trouble."  My assumption is that it was very low tech and they hid that fact with the liberal application of potting compound.  It would have been fun to put a current sensing resistor on the output and scope it to see how it performed.  The conclusion would probably have been "dumb."

I tried the search "fuzzy logic toaster" and there are no direct hits!  Damn!

MileHigh
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: TinselKoala on June 20, 2014, 07:35:54 AM
I'll settle for being an archangel, and write my code in c++.

 :P


Try "fuzzy logic clothes dryer"...   ;)
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: Farmhand on June 20, 2014, 07:58:28 AM
 :D I just gotta write whatever I can that will cause what I want to happen to happen. I was convinced that if I got a picaxe 08 I would be able to write simple code to do pwm outputs and stuff. Then when I got it and learned some commands I was able to do more than I ever expected, and know how much more is possible, almost endless possibilities.

Some of the commands are real doozies, the " if...then \ elseif...then \ else \ endif " takes the cake and I did manage to use it properly in one program. Boy was I chuffed.  :-[

I did also teach myself to assemble computers and flash BIOS chips and overclock the heck out of old 939 socket computers, I managed to overclock an Opteron 165 (1800 MHz) Stock up to 3200 MHz with only air cooling. Took a lot of tweaking the memory timings to have it run stable with only a small increase in core and memory voltages. I think the damp has killed all my old "fast" computer parts. I can get carried away with things. My bad.

This might make you laugh, a sign of generations, "Back when I was into building fast computers we had to use multiple mechanical hard discs and connect them up in a RAID 0 set up to get more data speed and then we only had a Hard disc not even nearly as fast as a Solid State drive".

Does anyone even do RAID 0 for speed anymore ?  Full of pitfalls a RAID 0 config.

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Title: Re: BroMikey's Capacitor Dump Circuit
Post by: MileHigh on June 20, 2014, 09:17:37 AM
I think it was made by Rockwell, but I can't remember the name of it.  You wrote assembler code on paper, converted it into hex by hand, and even calculated your jump-to addresses.  Then you entered the program byte by byte into memory with a hex keypad.  Then you hit the reset button and ran your program.

I think it's arguable that these kit boards in the late 70s and early 80s launched the computer revolution.  They were not toys, they were the real thing at the time.

Looking back in time sucked into the inverse-Moore vortex.  Try ripping a Blu-ray disc with one of these babies!
Title: Re: BroMikey's Capacitor Dump Circuit
Post by: M. Rowland on June 21, 2014, 12:28:38 PM
Nice machines Guys I gotta git one of those fancy controllers.

BroMikey