Print PDF
Favorite
Email
Hello Everybody!
After a year or so of reading and drooling over other people's wonderful projects in these pages I decided to finally make one of my own. Here is my first instructable, a version of the ever popular Battery Desulfator, which I built in an Altoids tin.
First, some background:
My urge to build this project came when my wife's car refused to turn over after a three day weekend away. Here in Tokyo, during winter, the temperature can drop to the low 20's (F) at night and since we have no garage, her car just has to endure the cold as best it can. Many people don't realize that you don't have put up with repeated jump-starts or run to the nearest garage and plunk down 7,500 yen ($85) for a new battery every time this happens. Your old battery may just have built up a layer of lead sulphate crystals on its plates and that is preventing the acid from contacting them over their full surface area. This is caused by subjecting the battery to long periods of insufficient charge, as in the cases of unplugged golf carts over the winter, infrequently used automobiles, and PV systems that don't get enough sunlight to charge their batteries. The result is a great reduction in the battery's ability to produce electricity.
With a desulfator circuit you can reverse this process and rejuvenate the battery to like new condition. You can also save money and prevent water and ground pollution at the same time by keeping your old battery out of the local landfill. As long as nothing is seriously wrong with the battery it can last many times the two or three years that people typically use them. You can even get free batteries from garages that routinely throw them away, desulfate them, and never buy another battery again. Save money and help the environment - now there's a green ecology scheme I can get into!
Most DIY desulfator circuits in use today can trace their roots back to an article in issue # 77 of Home Power magazine written by Alistair Couper in June/July of 2000. Many versions were spawned by his design but they all accomplish the same thing, that is, they use various pulsing circuits to force the lead sulphate crystals back into the electrolyte thus rejuvenating the battery and restoring its lost capacity. The version I chose uses an NE555P timer chip for the multivibrator front end and two coils, a low ESR cap, a fast diode, and an N-channel MOSFET (hereafter referred to as a FET) to generate the high voltage (50V) spikes in the output. Credit goes to Ron Ingraham for changing the design to use an N-channel FET instead of the harder to find and more expensive P-channel types in the earlier versions. Along the way I couldn't resist adding a few tricks of my own to make the design more convenient. See this link for a description of the theory and other information on desulfators.
This circuit can be used three ways - as a standalone device powered by the battery under test; as a standalone device but used in parallel with a battery charger; or built into a charger so that the two work together as one. I chose the third option for my circuit but added a switch so I can use either device independently. Mounting the device onto my charger also allowed me to use the charger's output cables for both functions and avoid the tangle of wires that inevitably results at the battery.
Once properly adjusted, the desulfator can be left on permanently whenever the charger is charging. Just be aware that no matter what configuration you choose, the desulfator is powered by the battery under test so if you use it without a charger care must be taken to avoid deep discharging the battery.
High power versions of these circuits can be built for off-grid solar-cell systems as well where many batteries are typically arranged in series/parallel banks and attached to inverters to produce 120V AC. These battery banks can be desulfated en-masse while being charged by their solar arrays for a truly self-maintaining system minus the periodic checks for electrolyte level, as long as the desulfator circuit is scaled up in size sufficiently.
The Altoids can is the perfect box for this project as the circuit neatly fits inside it and the metal construction can shield much of the RFI that may be emitted by the output stage. You can't beat the price of these tins, and they even come with free mints, or do the mints come with a free tin, I forget... ?
So with the background out of the way, let's get to work!
After a year or so of reading and drooling over other people's wonderful projects in these pages I decided to finally make one of my own. Here is my first instructable, a version of the ever popular Battery Desulfator, which I built in an Altoids tin.
First, some background:
My urge to build this project came when my wife's car refused to turn over after a three day weekend away. Here in Tokyo, during winter, the temperature can drop to the low 20's (F) at night and since we have no garage, her car just has to endure the cold as best it can. Many people don't realize that you don't have put up with repeated jump-starts or run to the nearest garage and plunk down 7,500 yen ($85) for a new battery every time this happens. Your old battery may just have built up a layer of lead sulphate crystals on its plates and that is preventing the acid from contacting them over their full surface area. This is caused by subjecting the battery to long periods of insufficient charge, as in the cases of unplugged golf carts over the winter, infrequently used automobiles, and PV systems that don't get enough sunlight to charge their batteries. The result is a great reduction in the battery's ability to produce electricity.
With a desulfator circuit you can reverse this process and rejuvenate the battery to like new condition. You can also save money and prevent water and ground pollution at the same time by keeping your old battery out of the local landfill. As long as nothing is seriously wrong with the battery it can last many times the two or three years that people typically use them. You can even get free batteries from garages that routinely throw them away, desulfate them, and never buy another battery again. Save money and help the environment - now there's a green ecology scheme I can get into!
Most DIY desulfator circuits in use today can trace their roots back to an article in issue # 77 of Home Power magazine written by Alistair Couper in June/July of 2000. Many versions were spawned by his design but they all accomplish the same thing, that is, they use various pulsing circuits to force the lead sulphate crystals back into the electrolyte thus rejuvenating the battery and restoring its lost capacity. The version I chose uses an NE555P timer chip for the multivibrator front end and two coils, a low ESR cap, a fast diode, and an N-channel MOSFET (hereafter referred to as a FET) to generate the high voltage (50V) spikes in the output. Credit goes to Ron Ingraham for changing the design to use an N-channel FET instead of the harder to find and more expensive P-channel types in the earlier versions. Along the way I couldn't resist adding a few tricks of my own to make the design more convenient. See this link for a description of the theory and other information on desulfators.
This circuit can be used three ways - as a standalone device powered by the battery under test; as a standalone device but used in parallel with a battery charger; or built into a charger so that the two work together as one. I chose the third option for my circuit but added a switch so I can use either device independently. Mounting the device onto my charger also allowed me to use the charger's output cables for both functions and avoid the tangle of wires that inevitably results at the battery.
Once properly adjusted, the desulfator can be left on permanently whenever the charger is charging. Just be aware that no matter what configuration you choose, the desulfator is powered by the battery under test so if you use it without a charger care must be taken to avoid deep discharging the battery.
High power versions of these circuits can be built for off-grid solar-cell systems as well where many batteries are typically arranged in series/parallel banks and attached to inverters to produce 120V AC. These battery banks can be desulfated en-masse while being charged by their solar arrays for a truly self-maintaining system minus the periodic checks for electrolyte level, as long as the desulfator circuit is scaled up in size sufficiently.
The Altoids can is the perfect box for this project as the circuit neatly fits inside it and the metal construction can shield much of the RFI that may be emitted by the output stage. You can't beat the price of these tins, and they even come with free mints, or do the mints come with a free tin, I forget... ?
So with the background out of the way, let's get to work!
Remove these ads by
Signing UpStep 1Circuit Schematic and Parts List
Here is the schematic and parts list, along with some of my pencil notes.
The list is complete except for some parts (two pots, two resistors, two switches, a LED, a FET and some grommets and pop-rivets) that I salvaged out of my junk box. Feel free to do the same, just keep to the values on the schematic as much as possible. Please note that C4, a 100uf 25V electrolytic capacitor, must be a "low ESR" type (Equivalent Series Resistance) to limit its tendancy in this application to get hot. If you choose to use trim pots instead of resistors for R2 and R4, as I did, be careful with the adjustments as C4, D2, L1 and L2 can get very hot if the 555 chip is made to send too wide a pulse into the output stage. The resistor values in the schematic should program the 555 chip to output pulses of the proper width and limit any excess heat buildup, however. We'll discuss this further in the Smoke Test Steps.
The LED can be any standard type and will only turn on when pulses are present in the output. S1 should have at least a 3A rating, and if you use a DPDT type use both sets of contacts in parallel to reduce the contact resistance as much as possible. S2, at the output of the 555, isolates the 555 from the output stage allowing you to make adjustments to the front end without risking overheating Q1, D2, C4 or the inductors.
The inductors I chose are listed on the schematic at the bottom of the "Possible Inductors from Digikey" list. They fit the can nicely but will need to have one lead extended slightly to reach the bottom of the circuit board. In retrospect, an inductor with a slightly higher current rating for L2 might be better as the one I chose gets noticably hotter than L1 even though it has the same current rating of 2.4A. Digikey part number M8875-ND should fit the can, barely, and has a 3.6A rating, but the 2.4A coil that I'm using now really only gets hot if I get too aggressive with the pulse width adjustments.
D2 is a FRED (Fast Reacting Epitaxial Diode) and should not be substituted with any old diode in your junk box as the latter will probably not work well in this circuit. If it gets too hot you can use two in parallel to double the current capacity, but again, if you keep the pulse width on the conservative side it will only get slightly warm.
The FET listed works very well and is inexpensive. I mounted mine directly on the perf-board with a piece of stick-on copper foil (available from Digikey) under it to act as a heatsink. In this configuration it doesn't get warm at all so the copper foil may not actually be needed. Be aware that the metal tab on the FET is also attached to pin 2 (drain) so if you attach the FET to a heatsink you'll have to electrically isolate it from the rest of the circuit. I also used a TO-220 transistor socket to allow easy replacements but you can wire the FET in directly if you prefer. Just avoid touching pin 1 (gate) while handling it as it is very ESD (static) sensitive.
Also, I opted to use the "Turn-off Enhancement Circuit", shown in the schematic as Q2, D3, and R5, as it helps the FET to turn off more precisely. If you use these parts do not use C2 and R3.
The list is complete except for some parts (two pots, two resistors, two switches, a LED, a FET and some grommets and pop-rivets) that I salvaged out of my junk box. Feel free to do the same, just keep to the values on the schematic as much as possible. Please note that C4, a 100uf 25V electrolytic capacitor, must be a "low ESR" type (Equivalent Series Resistance) to limit its tendancy in this application to get hot. If you choose to use trim pots instead of resistors for R2 and R4, as I did, be careful with the adjustments as C4, D2, L1 and L2 can get very hot if the 555 chip is made to send too wide a pulse into the output stage. The resistor values in the schematic should program the 555 chip to output pulses of the proper width and limit any excess heat buildup, however. We'll discuss this further in the Smoke Test Steps.
The LED can be any standard type and will only turn on when pulses are present in the output. S1 should have at least a 3A rating, and if you use a DPDT type use both sets of contacts in parallel to reduce the contact resistance as much as possible. S2, at the output of the 555, isolates the 555 from the output stage allowing you to make adjustments to the front end without risking overheating Q1, D2, C4 or the inductors.
The inductors I chose are listed on the schematic at the bottom of the "Possible Inductors from Digikey" list. They fit the can nicely but will need to have one lead extended slightly to reach the bottom of the circuit board. In retrospect, an inductor with a slightly higher current rating for L2 might be better as the one I chose gets noticably hotter than L1 even though it has the same current rating of 2.4A. Digikey part number M8875-ND should fit the can, barely, and has a 3.6A rating, but the 2.4A coil that I'm using now really only gets hot if I get too aggressive with the pulse width adjustments.
D2 is a FRED (Fast Reacting Epitaxial Diode) and should not be substituted with any old diode in your junk box as the latter will probably not work well in this circuit. If it gets too hot you can use two in parallel to double the current capacity, but again, if you keep the pulse width on the conservative side it will only get slightly warm.
The FET listed works very well and is inexpensive. I mounted mine directly on the perf-board with a piece of stick-on copper foil (available from Digikey) under it to act as a heatsink. In this configuration it doesn't get warm at all so the copper foil may not actually be needed. Be aware that the metal tab on the FET is also attached to pin 2 (drain) so if you attach the FET to a heatsink you'll have to electrically isolate it from the rest of the circuit. I also used a TO-220 transistor socket to allow easy replacements but you can wire the FET in directly if you prefer. Just avoid touching pin 1 (gate) while handling it as it is very ESD (static) sensitive.
Also, I opted to use the "Turn-off Enhancement Circuit", shown in the schematic as Q2, D3, and R5, as it helps the FET to turn off more precisely. If you use these parts do not use C2 and R3.
Desulfator Schem & Parts List.pdf(781x601) 1 MB| « Previous Step | Download PDFView All Steps | Next Step » |
http://1.bp.blogspot.com/_X7IYGjOz8_0/SljTnoVMhPI/AAAAAAAAAII/8W4Q7qxwhfY/s1600-h/hi-low+charger.JPG
Because I rockie in eletronic, can you and other see and coment. This is the blog http://poormanguides.blogspot.com/2009/05/updated-chargerdesulfator.html
Yikes! You're playing around with straight 120V AC with no isolation! Touch one wire and you could receive a nasty shock, and if any hydrogen gas is around (as would be the case if any deeply discharged lead-acid batteries are nearby), one spark and an explosion is possible. If electrolytic capacitors are used and are wired up backwards, they can blow, possibly providing that spark. That said, I can't comment on if or how well it works without building and testing it myself. I can only take the author at his word that it does, and at the moment, I have no reason to doubt him. However, my circuit uses lower voltages and takes more time, but it is safer to build and use. For those of you with little or no electronics background I recommend you seek professional help before attempting this circuit.
I am very glad to be a member among all cleaver and high educated members.
With regards to all
I am : asad al hakeem from IRAQ
Also, if I insert 15K, 270K and 0.0047ufd in all those calculators available on the internet, it shows a 50% duty cycle with 500Hz.
Can you pls help here. I seem to be doing some wrong ?
My circuit is working. I hear the very faint humming noise. My Q1 is almost cold, L2 is 6A rated so almost cold. L1 is almost hot. C4 ( i have used 5 22ufd in parallel, so they are luke warm), the 2 FR306 are slightly warm.
My L1 is rated at 2.2A. Any views on why only that component gets hot ? May be its because its rated at 2.2A and the current flowing through it is higher or close to its rating. Is it a must that L1 should be 1000uh ? can i replace it with a 220uh as I have more of them and they are rated at 6A.
What is the effect if I use a 180ufd capacitor instead of 100ufd ?
I have a 200AH 5years old inverter battery. After leaving the inverter connected for 8 hrs and then disconnecting, the no load voltage of the battery is 13.5V. However, as soon as I connect the inverter and start my fans and tublights in the house, within 5 min, the voltage drops to about 10V and the inverter trips due to low battery voltage.
If I leave the inverter connected for 8 hrs to charge the battery fully and then disconnect the inverter and then connnect the desulfator, the voltage starts at 12.4V, the components get heated, faint 1Khz noise heard etc and then after 8 hrs, the voltage drops to about 11.3V and the heat in the components is also reduced which indicates that the desulfator is not able to take up enough current from the battery as its discharged....
From the above description, do you think this battery is a good candidate for resurrection using this desulfator ? I have left it connected for last 2 days and I am not noticing any significant regneration of power in the battery... may be I should leave it connected for several weeks.
I am also thinking to use a R-C voltage doubler kind of a circuit across the battery to check the max ripple voltage using a voltmeter. This will also help to ascertain if the circuit is really ringing and providing the pulses. I guess this may be a slightly accurate way instead of the touching components for heat or the LED (which in my case does not glow, may be because I have connect two FR306 in parallel)
Also, I'm not too keen on your voltage doubler idea. The spike can be two or three times the amplitude of the ring that follows it and it can be 50 volts or more in amplitude in a working circuit. The best way to see it is with a fast scope. I use an old Tektronics 200 mHz analog scope that requires a bit of knob finagling to get the spike to show itself. Deep down in the Comments section you can see pictures of the spike that I took from this scope. A 100 mHz scope might be hard pressed to see the spike, if it can see it at all.
Thanks for your responses. Unfortunately with no scope handy and no budget to a new one, I have to keep experimenting.
I have used a simple diode and capacitor as a peak voltage measurement tool. When I connect a 10 ohms, 50W resistor as load to the circuit and power it through a 12V, 10A SMPS supply and connect the peak voltage circuit, I see about 45V at the D2 and about 37V at the resistor load.
However, when I connect this to the battery and do similar measurements, I get around 20V. So not sure, why the voltage drops so much at the battery.
May be there is a lot happening out there....
Some more observations as I continue to work on this
Lets say A and B are points of + and - on the ckt board and C and D are points of + and - at the tips of the cables
Now to test the circuit, instead of using a battery, I used a PC power supply SMPS to provide 12V.
When no load is connected, the readings are
A to B 48V
A to D 42.5V
C to D 40.8V
When I connect a 10Ohms, 50W resistor across C &D, I get following
A to B 45.9V
A to D 39.8V
C to D 38V
Now, to further experiment, I connected a Power Diode to the positive cable of the SMPS ( so that the pulses don't enter the SMPS) and here are the readings
No load
A to B 61.9V
A to D 61.4v
C to D 62V
When I connect the 10 ohms, 50W resistor, the readings
A to B 49.2
A to D 48.2
C to D 48.3
Also, I noted that when I connect the SMPS through a diode, and without any load to the circuit, the transistor quickly start heating and gets hot. This indicates that all the energy in the inductors is finding its way only through the transistor.
However, when I connect this to the battery, the readings at battery is around 20V.
So my conclusions.
1. The voltage drop is majorly due to the sulphation in the battery and not due to the leads or the peak detection circuit. Now should the voltage drop from like 48v to 20v is a question I have no answer to. In your case, you get 36V. But I guess yours was a simple small Car battery which are I guess 40AH capacity. Mine is a huge inverter battery of 160AH capacity and is a 6 years old regularly used battery and has stopped providing much of capacity so indicating that there is a lot of sulphation.... so may be the voltage at the battery terminals is an indication of how much the sulphation is... :)
2. My idea of the peak detection really worked. Its a simple circuit of a diode and a capacitor connected across the measurement points. You commented that it may be loading the circuit, but since there is a diode, I think once the capacitor is charged to the peak point, it would stop drawing any current and thus not really overload. This is a very easy fix to the costlier option of buying an oscilloscope.
3. I have also changed the wiring of the 555. I used the circuit and calculations available at
http://www.horrorseek.com/home/halloween/wolfstone/TechBase/com555_555TimerCalc.html
I used R1 = 29.3K R2 = 322K and C = 0.0041ufd
This as per calculations gives me 8.34% duty cycle and 1000Hz freq. Now since i did not have a scope, I chose to this config so that I atleast have some calculated proof of the frequency. The inductors are humming and that is another indication that the circuit is really working at 1Khz.
Enough !!! I guess I am going to stop any more experiments and leave the circuit connected to the battery..... for weeks and weeks and hoping that some day, the sulphation cracks up and I get a better performing battery....
Your peak detector is a good idea. It certainly is a cheap alternative to buying a scope. However, without being able to see the waveform, it's hard to tell how much noise is in the circuit. The FET will heat up drastically if it receives noise from the front end. Keeping the circuit runs short helps there. In severe cases you might have to use a grounding plane.
Good luck with your circuit!
The schematic is essentially a switching DC-to-DC converter, 12 VDC to high DC voltage spikes. It takes 12 VDC power from the battery and pulses it back into the battery as a voltage spike using a technique similar to an automotive points controlled ignition system. The pulse rate is set by the 555 timer chip, U1 (distributor shaft) which switches the MOSFET Q1 (points) at a 1 kHz rate. When Q1 is in the non-conducting state, current is drawn from the battery through L2 (ignition coil) so it charges capacitor C4 (condensor) slowly. Q1 is then switched on for 50 microseconds causing C4 to discharge through L1. When Q1 is switched off again, the stored inductive energy in L1 pulses back into the battery through diode D1. This pulse of current can be as high as 6 amps but has a very short duration. The use of an inductor to supply this high voltage pulse is what makes it possible to restore a badly sulfated battery with a high internal resistance. The peak voltage applied across the battery can be as high as 50 VDC. This voltage will decrease as the battery's internal resistance declines or its function is restored to normal.
Looking at the circuit, when Q1 is not conducting, capacitor C4 will charge through coil L1. And when Q1 is conducting, C4 will discharge through L2.
Pls let me know if I am wrong.
I could not find good ESR resistors. So I brought 5 small 22mfd, 16V tantalum capacitors and connected them in parallel. Within first 15min of connecting to battery, 1 of the 5 blew up. Maybe the capacitors are not right.
I am still thinking what capacitors to put ? 100MFD, 25V electroylic may not be a great idea as they have higher ESR... what kind of capacitors are recommended ?
Pls suggest.
Has any one attempted to take pictures of the battery through the water holes before and after the sulfation ? May be that is a good idea to see how the desulfation is progressing.
The pdf in the instructible lists the proper part number for the low ESR cap. It works well, is very small, and fits the Altoids can. Other builders have used substitutions for this part with varying degrees of success, but no one has found one as small or smaller. They can be found listed in the Comments section below the instructible.
thanks for your quick response.
I used a green color LED and when connected as per the circuit diagram in the pdf, it did not light up.
So, i reversed it and it did turn up bright. I guess the IRFZ44 switching gave enough current to the LED to bright up.... however, with that arrangement, do you think it would alter the functioning of the circuit ?
My 1000uh coil is warm, the FR602 and capacitors are warm too,,, and IRFZ44 is almost cold ( very little warm). The coils do make humming noise, but that is heard only when i take my ear very very close to the coils... may be my coils are of good quality with a magnetic core ( got it from coil craft).
I will try to order low ESR aluminium electrolyte capacitors from digikey.
I have found a desulfator online for $30.99 ($3 more than the minimum cost of parts for this build) and the description says that the timer is CMOS. This led me to assume that it might be the TLC555 timer that you mentioned in note 5 of the circuit diagram. The picture is not detailed enough for me to see the timer's ID label but I could ask if I need to.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330507460322#vi-content
My question is:
Is it possible to replace the TLC555 timer (if that is the timer on the board) with the NE555?
I know that the rest of the circuit on this desulfator is probably critical to the answering of this question. I only ask it because in note 5, it seemed that you were suggesting that the two timers were interchangeable. I wanted to find out if this was the case because simply upgrading this ready-to-use desulfator with a $0.47 timer from Digikey would be amazing. It's a long-shot, but I though it was worth the asking.
I know the image is small, but maybe it can help.
Having said that, I have no idea how well this device works, though I don't doubt that it does so at least well enough to justify its cost. The advantage in building your own is in the lesson in electronic assembly and design that it provides. For tinkerers like me, that's priceless.
Q1: if I had a 4 baterry conected in paralel and instal on each one desulfator, will it be ok to charge with 12v max. 8 Amp charger or it must be mah 2 Amp and will be the charger fine I don't want to burn the charger in the midle of the night.
Q2: I overcharge one death 55 A car batery lefted to charge on 10A for 5h, it heated and voltage drop Immediately. The question is: if I use desulfator will it fix it.
*I wait the update of the desulfator with new features of course if you have one