Hi everyone,

After reading so many articles on Battery desulfator i've decided to come out with my version of Battery desulfator using
Microchip base micro-controller using PIC12F629 or PIC 12F675.

"Please pardon my english" .I don't really have time to check for minor grammatical errors.

Before we begin this circuit although simple in design requires DIY builders to have at least basic PIC programming knowledge with electronics.

Honestly i had no programming knowledge initially.I started on my own on how to blink led using Pic micro-controller. 

I have used this circuit i design to recover 5 Maintenance -free battery ranging from 12volts 2AH (UPS battery) to 7.2AH (Previously used in electric bicycle).I have not attempted to recover a CAR battery since i don't have any old battery in my home.

I have recovered battery eg:2AH which had voltage as low as 0.9v which i have not charged  for around 8 years after removing battery from a defective home UPS.
I  have managed to recover 4 12v 7.2AH battery which i have not charged since 2004.These batteries were in my self assembled electric bicycle years ago.

These batteries were all recovered in within 48hours.For a car battery it would take weeks maybe.

Battery desulfator circuit i used while with charging battery with 12volt 500ma transformer.
I'd believe using slow and steady approach do produce better result most of the time.

The frequency output from Pin 7 is 56us on with 1ms off in a infinite loop.
During programming i have set it to use internal 4MHZ PIC oscillator which have 1% tolerance and i have disabled reset /mclr.
There is only 3 connection to pic.

I noted the current consumption of the desulfator circuit is around 13 to 15mA with a well desulfated battery if connected to the charger with voltage around 13.8volts.

I noted if a old battery needs to be desulfated the voltage would increase up to 17.xx volts on
battery with desulfator  circuit consuming about 40 to 50mA.

The D1  diode i used is the fastest recovery diode i could find with 25ns response time.
The purpose of D2 is to prevent accidental polarity reverse at the input to protect the circuit.D2 could be replace with higher amp rating like IN5820 if needed.
It's better to obtain C1&C2 capacitor which have a low ESR rating with at least 50V.
For L2 toroid if you could get anything from 170uh to 220uh would be sufficient.Please do not wind higher than 30 turns as the resistance would increase and hence lower the circuit efficiency as well.To be honest i don't know the uH rating for my self made toroid but i got results which what matters in the end.

For the mosfet if you could find a lower turn on resistance with low turn on/off delays which will definitely improve the efficiency of the circuit.

I have connected a piezo speaker temporarily to old battery which needs to be charged since it would have higher internal-resistance.i noticed the piezo speaker would emit a loud 1KHZ sound.But if the battery is already well desulfated i noticed the piezo speaker connected temporarily to battery would hardly emit any sound at all.  
We could use piezo speaker as a quick way to test to know if battery to be charged is well desulfated or internal resistance of the batery is already being lowered.

To really know the estimated internal-resistance of battery we would have to use 1Ohm maybe 50w resistor idealy  1% tolerance.
But normally it's more easy to find high power resistor with 10%
tolerance instead.

To increase internal-resistance measurement accuracy.It's best recommended we wait about 12hours after battery is disconnected from charger and circuit.

Formula to check internal resistance of battery.

(Battery voltage after charge) - (battery voltage after 1ohm resistor connected connected for around 5 seconds or once battery looks stable)      *         1  (Resister value in ohm.But if your resistor have 5 or 10% tolerance.It best you take min and max value eg:0.9,1.1)/(Battery voltage after charge)

(Original Battery voltage - Battery voltage with 1ohm resister)   x     (1/(Original battery voltage).

If you could get below  ".1ohms" means the battery desulfator circuit have done a good job in recovering your old batteries.

I have uploaded the source code merely as an example and hex file which you could program the pic with any cheap USB pic programmer.I'm using KIT150 USB PIC Programmer.

http://members.lycos.co.uk/sanjev17/desulfator.c        (Deleted by source webadmin)

http://members.multimania.co.uk/sanjev17/desulfator.HEX  (Deleted by source webadmin)



<p>Help please! Does anybody have a hex file to program this PIC? Thank You in advance!</p>
<p>The very latest commercially available desulfators are now very low cost and of course you can be sure they work. Try this link to a see what is available www.recovermybatteries.com </p>
<p>The very latest commercially available desulfators are now very low cost and of course you can be sure they work. Try this link to a see what is available www.recovermybatteries.com </p>
<p>we use a Battery Extra, to be honest the price is such that it does not seem worth trying to build your own... check it out <a href="http://www.recovermybatteries.com" rel="nofollow">www.recovermybatteries.com</a> </p>
The scheme can not be correct. The anode of D1 should connect to the drain of fet.
Please explain how this can work. Assuming the &quot;6 to 12 volts&quot; is the battery your are trying to rejuvenate that means that you must be powering your circuit from another source. So where should it be connected? I am guessing that it is across C3 and C4. Also I am guessing it needs to be 5 volts. Also is the 30 turns centre tapped at 15 turns or is there some different ratio? <br>Thanks
The source of power for the circuit is the battery(Take note of the symbol for cell) itself while the battery is being charged from another source. <br> <br>
Thanks, I think I might build one then. I could not see how it would work running from an old, discharged battery, and did not see anywhere that the battery itself was being charged while this was working.
Now I have read it again I see you said &quot;Battery desulfator circuit i used while with charging battery with 12volt 500ma transformer.&quot;
Hi, thank you for a nice project. I am in the process to build this project but the C codes and hex codes is no more available. Can you please where can I get it ?
It seems the code was deleted by http://members.lycos.co.uk web admin i think. <br>I don't have a copy of it locally. <br>The original was in c you could use any programming lang <br>This is how the logic works <br>Infinite loop <br>{ <br>on <br>delay 56us <br>off <br>delay 1000 ms or 1s <br>} <br> <br> <br> <br>
Hi Michael <br> <br>Many thanks for your reply. I have ordered two low ESR (0.03 ohms) 47uf caps and intend to build the circuit soon. If the circuits works as intended then as the car battery is desulfated, the SG of battery electrolyte should rise indicating that it is working. Will keep you posted. <br> <br>Cheers. <br> <br>Peter.
Hi there, thanks for the circuit which i am in the process of building. When you mention low ESR capacitors for C1/2, what is the highest acceptable ESR for the circuit to work well? <br> <br>Thanks. <br> <br>PS: can i use it condition a 12v car battery?
You need to look for low ESR capacitor to increase efficiency. <br>Else get standard 2 x 47uf caps and run it in parallel. <br>Go for 50v cap at least as i noted voltage surge could go high as 44v for battery that needs to be shocked. <br> <br>There is no risk of accidental polarity reversal for my circuit with the Diode D2 in place along with 500ma fuse. <br> <br>I have not tried on old car battery yet but i believe this circuit could prolong car battery life to a certain extend. <br> <br> <br> <br> <br>
Thank you for this circuit. <br> <br>I was able to make this circuit using a 12F683 and some spare parts I had lying around. I believe your diagram shows diodes D1 and D2 in the wrong place, and resistor R2 isn&rsquo;t needed. <br> <br>This device worked better than expected. After connecting device to an old UPS battery I noticed a big improved within an hour. <br> <br>PS. 50us pulses at 1.2Khz worked great for me <br> <br>Thanks again for posting this circuit! <br>
Hi,<br><br>Thanks for trying out this circuit.<br><br>I do admit R2 is optional.But i have accidentally destroyed my Mosfet if PIC is removed from circuit and powered on.<br><br>That's the reason why Resister is normally used to protect mosfet gate.<br><br>The diodes are in the right place.D2 was the additional component which also prevent accidental polarity reversal and help to improve the circuit efficiency since pulse could increase to 56us.<br><br><br>
Hi, where are connected transformer in the circuit 12volt 500ma transformer can you show me.<br>How many amps have L1,L2 toroid?
The 6 to 12 v is the symbol for battery.
I have found that 3,26 MHz is optimum it is magnet-resonance, can you program at that frequency I ' m rookie at electronic.

About This Instructable


30 favorites


More by michaelsanjay: PIC12F629 Lead-Acid Battery Desulfator
Add instructable to: