Battery Desulfator Kit, TESLA 12V compatible

I Have observed after 3 separate tests using 3 separate 250AH , 12V sealed batteries that while CCA increases  usefully after only one cycle of Regeneration, The Ah capacity increases  in steps of about 25% with repeat Regenerations.

For instance at the onset the Battery was at 50Ah capacity, 225 CCA

Regeneration cycle 1 = 75AH , 400 CCA

Regeneration cycle 2 = 90Ah, 400 CCA

When I speak of regeneration ..that applies to the automated product based,in part, on the circuit presented here. Here are the main principles of the micro-controller run system.

The regeneration cycle is as follows:

1) Initialization =>  battery tests for Voltage & Impedance

2) Viability cycle => discharge to 11.9V for a 12V battery or 5.95V for a 6V battery

3) Pulsecharge at C/20  until the battery is up to 13.2V

4) Absorbtion test => 20 minute discharge at C/20  to validate battery voltage >11.9V or 5.95V for a 6v.

6) Pulse charge & reflex charge in stages with thermal/voltage sensing feeding Pulsewidth control and Amperage.

6A) Ensure a minimum absorption voltage (14.4V, temp. corrected, achieved  and then voltage limit to 14.1V for 2 to 8 hours depending on size of battery.

7) Battery rests for 15 minutes and is  discharged  at C/8  to C/13 for 2 hours and capacity calculated based on Peukert analysis.

8) Pulse charge  again with a 2 hour absorption/voltage controlled profile termination.

9) Rerate CCA and report on battery AH.input, final AH capacity (C/20)  , resting V, temperature  and CCA & Impedance.

Ok, so I can finally say this has transitioned to product stage. A few customers achieved and now manufacturing of the 1st 125 production units has started.
Along the way I did some testing on 150Ah deep cycle batteries and improved the s'ware to handle them better as they have different thermal characteristics and stronger construction than starter batteries.

The system uses both PIC and ESP12 processors to handle processing and communications independently.

The online interface is working ok with real time science  telemetry coming back from as far as Africa now. Customers can monitor their accounts with multiple re-generators running.

I am adding a wifi LED indicator to the front panel as WiFi loss is an issue for the telemetry.

An automotive brake lamp combined with a Kilo Amp schottky pulse diode now handles back emf pulses from the battery and runs the output FETs mucg cooler in their SOA with no more FET avalanche burnouts.

Replaceable battery clamps now use spade connectors and #12 AWG copper cabling x 2. Battery clamps are now tinned with lead/tin solder to counter galvanic clamp corrosion from battery out gassing.

I have determined that in addition to de-sulfation, removal of dendrite hydrate crystals which cause cell shorting is also happening, but it can take a couple regeneration cycles for the tougher hydrate crystals. They are characterized by loss of voltage from a cell (e.g. a 10.5 to 10.8V output from a 12V battery) and cell heating during the multi hundred amp pulse process. Note that they have the same symptoms as a plate sludge shorted cell, but deep cycle cells (AGM) don't develop sludge shorts.
http://www.power-thru.com/documents/The%20Truth%20About%20Batteries%20-%20POWERTHRU%20White%20Paper.pdf

Something to remember when rating batteries of any kind.

What matters is Watt hours or Kilo Watt Hours as per your utility meter.

A lot of batteries are rated in Amp hours though and that's a bit misleading.

When rating a lead acid battery, it is discharged to 10.5V and the Ah discharged at a C/20 rate is the standard 'rating'. So a 100Ah battery will discharge 100Ah at a 5A rate for about 20 hours.

Faster discharging brings in the Peukert factor into significant play and this has to do with electrochemical and energy losses due to chemical changes inside the battery and heating.

Now "counting" Ah is a common thing done on installations that hope to monitor charge efficiencies and battery performance. Charge Ah in vs discharge Ah out.  Discharge: Charge ratios of 80% eff. is a number experienced with lead acid batteries.

HOWEVER,  with pulse charging things will change. Efficiency can go DOWN at high pulse levels.  heating losses I*I*R become significant. Since pulse charging requires a significantly higher supply voltage, you must consider Wh and not Ah as a measure.

I recently processed a Caterpillar diesel SLI battery. It was showing around 40Ah discharge BUT only with 27Ah charged.  Well...the supply V I use is 36V, so we're actually looking at 36V * 27Ah =  972 Wh inputted vs an average 12.1V x 40Ah = 484 Wh discharged. Which ballparks to a 50% charge efficiency.

Seems about right since the 200A battery clamps get a bit hot during the pulsing (100's of Amps) , with ONLY 2.5 mΩ loss at the battery clamps causing the heating.

There's a bit of mild heating in the 12AWG x 8 cabling as well but some of that is conducted from the terminals. The cabling adds about 8mΩ to the loss.

Well, with a charge eff. of 50% , why do charging with this system you might ask?

Well here's why:

You are dynamically stress testing each battery well beyond it's service environment to be able to qualify the battery as suitable for service and not about to die off unexpectedly from borderline internals. No regular charger does that....as i am sure we can all attest to.

This is necessary when bringing back borderline or dead batteries. You need to know they will stand up.

No 'battery vitamin' or chemical additive will inform you of this NEED to KNOW info.

Ok, it seems that Autodesk has killed off the 'Freemium" version of EagleCAD. Well, that drops a large rock in the open source pond.

I learned EagleCAD on the Freemium license...ah well.

I added the 1:1 scaled PDFs in the files section to allow DIY toner Transfer PCB making of the double sided 5..5" x 3.25" PCB. Note that my layout has custom SMD pads for the TO247 IRFP3206 NFETS. Bend the Transistor leads at 90° just at the thick lead shoulder and trim down the bent section to 1/8".

I did that to make for an improved, low impedance solder joint that permits easy rework when experimenting with other transistors. It's a B*itch to remove through hole TO-247's  without overheating the drain connection and lifting the PCB copper. Also, it provides for easy transistor realignment if you don't get your heatsink 6-32 mounting holes just right. Hot air is advisable, or solder wick when doing rework.  I use a medium spade tip and about a 310°C setting on my solder station for the TO-247 rework.

290° C is ok for first installation.

As always, check out my other projects for DIY PCB making at home.

I've uploaded the EagleCAD schematic & PCB layout files along with some useful ref. info on batteries and desulfators.

The schematic layout is a bit spaghetti like, I'll neaten it up at some point, but it isn't very complex.

I have to add a text file or embed some text in the schematic to explain the operation and discuss the component selection. There are 5 basic blocks:
1) The capacitor bank (Low ESR)
2) The NFET bank (ruggedized for hi pulse currents)

3) The Opto-isolated gate driver for the NFET bank.
4) The reverse voltage tolerant power snubber
5) The fail safe crowbar (for the main fuse) for the snubber lamp.

As noted before, use OFC #12 AWG cabling, two pairs per battery terminal with crimped 1/4" spade receptacles to match the PCB spade terminals. Heavy duty 100A or 200A battery clamps (pictured in files section) are used and the ends of the two pair cabling (per clamp) are soldered right up into the jaws of the clamp to minimize clamp losses.

Many desulfators you can buy or find on EBAY deliver only a handful of peak Amps and very low overall average power, in fact many of them suck power from the battery while pulsing and you end up with a discharged battery in worse shape unless you have a charger attached. Thus pulse charging solves a number of issues at once. Battery charging, desulfating & dendrite destruction.

Now the key to the removal of sulfate and destruction of dendrites or 'mossing' is significant power delivery and elevation of the cells' voltage to equalization levels. This also gasses the battery and removes electrolyte stratification, desulfating without gassing is going to take a very long time, if ever.

The limit on this is cell temperature as heat is generated by forcing current through the resistive sulfate and the low concentration of electrolyte. Battery temperature should not exceed 50°C.

The pulse delivery circuit in this project will deliver RMS average up to perhaps 10A and perhaps up to 1000 pulse amps with adequate heat sinking and forced air cooling.

This requires a decent DC supply of 36V @ 11A or 400W, many 'MeanWell' types are available on EBAY. I use 8.8A, 36VDC supply or better and limit power delivery to about 7.5A max RMS as I run the system 24/7 with no a/c in the tropics.

Worthy of mention is reflex or pulsed negative charging as well, as this has proven to be effective on stubborn batteries with crystalline sulfate. I use it, however this output board doesn't offer it. That's a different circuit element, but you can achieve it easily with a switched 12V lamp load. What this achieves is a reduction of bubble nuclei which form on the plates during charging and thus improves the electrolyte to plate contact surface and hence overall charge efficiency ramps up.

On the matter of energy efficiency, battery impedance can range from a few milliohms when new to a couple K ohms when sulfated badly. Now efficient power transfer theory states that max. efficency takes place when the supply impedance is equal to the load. Well since large amounts of power move when the load is high (small battery impedance) the goal is to achieve a very low impedance pulse charging circuit, which this one does. Overall it's somewhere around 10 millohms when built properly mainly limited by the capacitor bank. A useful trend is the capacitors ESR drops as they heat so their operation improves when hot, limited of course to there spec. operating temps.

Until the next update.

Ok, I have some work to separate the pulse engine schematic from the rather complex overall circuit.

Once I do that I can publish the EAGLECAD files and BoM for those who want to get started.

Then I'll design an integrated pulser with variable duty cycle/freq to drive this engine for the DIY folks, although a simple 555 circuit can do it as well if you want to get going quickly.

In the meanwhile have a look at my other project, the Lead Acid Ah capacity tester/ logger. It is what I used when I was in early development to easily load test regenerated batteries and output the result to Excel to chart the battery Ahr. The principle of that unit is integrated into the complete system which does pass/fail rejection and rates each passed battery for proper service application.