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!
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Signing UpStep 1: Circuit 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
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The other battery is a wet lead acid 44A, peering inside the vents I see that the lead plates appear to be clean(dark brown), there is like a paper seperation sheet which has what looks like a grey powder on it this is also 12.45v standing charge (has been standing for a while).
Am i correct in saying that as the desulfation process continues the peak voltage declines as the lead sulfate disolves (I'm sure I read that somewhere).
Changed the 220uH 2.4 Amp to a different unknown type runs much cooler (less turns but thicker magnetic wire than the old one) the tone produced at 0.70A (as in smoke test 1) sounds more pronounced
When I do a voltage test on the output section (eg on D2) of the circuit it never exceeds the voltage of the test battery being desulfated. I say this because other videos on youtube have had voltage output of inexcess of 46V(is this correct for this circuit also). Capacitor C4 (100UF Electrolytic LOWESR) did explode so replaced with a new 1000uF Electrlytic LOWESR type this is now cold.
R2 = 6.1K
R4 = 150K
AMPARES to battery as in smoke test 1 = 0.50A on multimeter.
Have tried to locate the diode noted in previous comments not found as yet, have also read your comment with regards to how the circuit works, makes excellent reading.
Any ideas from the overheating description i provide above. thank you for your help.
Voltages on the Inductors also show only 13v max.
Parts used
Q1 = IRFZ44N
Q2 = 2N2907A
L1 = BOURNS - 2324-V-RC - INDUCTOR, TOROID V, 1000UH, 10%,2.4A
L2 = Inductor 220uH 2.4A Toroid Bourns 2116-V
Only been into electronics for a few months, a few small projects, this build certainly had me scratching my head a few times.
1/ smoke test 1, Ckecking the current with R2 as a Pot set at 15k, R4 Pot set to 270k, my multimeter is set at 10A, the reading is 0.07A, I was expecting 0.7A.
2/ I do get the tone once connected, I also get the Interference on my AM Radio.
3/ If I turn R2 Up to get 0.70A my 220Uh Inductor gets extremely hot so much so that I have had to fit a Cooling fan.
4/ I think that it is working a little as the battery I fitted it to has has had an increase in Standing charge/Voltage.
5/ the 220uH Inductor I have is rated at 3.4A, the 1000Uh inductor is rated at 2.4A both toroid inductors.
I have checked and rechecked the build against the schematic and I believe that I have done everything correct, I am not an electronic guru, just started about 3 months ago, can read simple schematics,
First (round) one is has two windings, each half of the toroid and 2.33 mH, with a measured 0.17 ohms.
The U-shaped one has even bigger gauged wire, is a single inductor, 873 uH and 0.07 ohms.
Both resistances measured with a regular multimeter, so DC.
I have a couple of the pcb's where these came from, so could easily use the U-shaped for both L1 and L2.
Or should I search for some other coils?
Thanks!
Cheers!
The car is a Peugeot 205, no ECU in it, and the Pioneer radio seems unaffected, no 1kHz signal from the speakers in any mode, exept AM receiving, certainly :-)) . Now it's cyclic desulfating, as i don't like to leave alone this proto. Results-i will come back and tell!
Ahm, LED. I got a white one, and that works only in reversed. It shows that the FET opens, and i think its enough to state that pulses are generating. But i will try red ones later.
During the winter my car's three year old battery decided it wasn't going to start my car on a cold morning so I jump started the car and took it to a battery dealer for his assessment. Naturally he said it was toast and that I'd better replace it. Hah! I said. I put it on the desulator and two months later it was good as new. Even tested it by leaving the car parked unattended for a week while I went on vacation. The car started right up when I got back.
I've made and assembled the circuit, made my own inductors as they were unavailable in the market. I can hear humming sound from the inductors, but have to place my ears very close. the led is also glowing but when i checked voltages and ampere with multimeter the dc voltage was 15v as i think because of zener diode and the current is just 0.1 amp this is not good can you tell me where i m going wrong?
Kmpres i was giving a look to charger section of your instructable, i was unable to to understand.
Did u attach the circuit parallel to charger and then attach it with battery?
If you attached parallely doesn't it affect the charger?
Or If u really attached parallely with charger can i use power diode to stop pulse going into charger, kind of insulating charger from the circuit output but on the same time using charger current as source?
Use a 1.5 to 2 amp trickle charger and leave it on while the desulfating circuit is in use. This will power the circuit and maintain the charge level at the same time.
I did make one change to my desulfating setup, however. I replaced the Japanese charger you see in the pictures with a Schumacker 1.5 amp Battery Companion slow charger (available on eBay) and attached 1 foot long leads and some simple battery clips to the desulfator circuit . The shorter leads allow a higher spike to reach the battery with less loss occurring in the wires.
Bro, i want to test this circuit on a 12v 200a wet cell battery, what i want is to give it life again in a week, what certain changes do i needed to do in your circuit? can u help me out.
As i read your previous comments i think that this circuit can work on one ampere hour ratting. if i am right the circuit will take 200 hour to fully refresh the battery.
here i have a power break down issue and i want to use it as soon as it get refreshed minimum i can wait is one week. so please help me out.
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