BroMikey's Capacitor Dump Circuit

[MarkE]

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  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.

[TinselKoala]

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.

[Farmhand]

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

[SeaMonkey]

BroMikey has made a video 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.

[SeaMonkey]

BroMikey continues to work with and improve
his CapDump Circuit.  He's asked a question 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.