In this article we investigate 4 simple yet powerful battery desulfator circuits, which can be used to effectively remove and prevent desulfation in lead acid batteries. The first method uses PWM pulses from a 555 PWM circuit, the second method implements an ordinary bridge rectifier for implementing a 100 Hz frequency based desulfation, the 3rd concept involves high voltage spikes, while the fourth design discusses desulfation using a 555 IC based high amplitude current pulsed circuit.
Sulphation in lead acid batteries is quite common and a big problem because the process completely hampers the efficiency of the battery. Charging a lead acid battery through PWM method is said to initiate desulfation, helping recover battery efficiency to some levels.
What is Sulphation in Lead Acid Batteries
Sulphation is a process where the sulfuric acid present inside lead acid batteries react with the plates overtime to form layers of white powder like substance over the plates.
This layer deposit seriously deteriorates the chemical actions inside the battery while charging or discharging making the battery inefficient with its power delivering capabilities.
Normally this happens when the battery is not being used for long periods and the charging, discharging processes are not done very frequently.
Unfortunately there's no effective way of tackling this problem, however it has been researched that the jammed sulphur deposits over an effected battery may be broken down to some extent by subjecting the battery to high current bursts while charging it.
These high current charging pulses should be well optimized through some control circuit and should be diagnosed carefully while implementing the process.
1) Using PWM
Implementing the method through PWM controlled circuit is probably the best way of doing it.
Here's an excerpt from wikipedia, which says,
" Desulfation is achieved by high current pulses produced between the terminals of the battery. This technique, also called pulse conditioning, breaks down the sulfate crystals that are formed on the battery plates. Short high current pulses tend to work best. Electronic circuits are used to regulate the pulses of different widths and frequency of high current pulses. These can also be used to automate the process since it takes a long period of time to desulfate a battery fully."
https://en.wikipedia.org/wiki/Talk%3ABattery_regenerator
The circuit of a PWM battery charger discussed here can be considered as the best design for carrying out the above desulfation process.
How the Circuit Functions
The IC 555 is configured and used in its standard PWM control mode.
The output from the IC is appropriately amplified through a couple transistors so that it is able to deliver the said high current pulses to the battery which needs to be desulfated.
The PWM control may be set at low "mark" ratio for implementing a desulfation process.
Conversely if the circuit is intended to be used for charging normal batteries, the PWM control may be adjusted for generating pulses with equal mark/space ratios or as per the desired specs.
The controlling of the PWM will solely depend on an individuals personal preference, so should be done correctly as per the battery manufacturers instructions.
Failing to follow the correct procedures may lead to fatal accidents with the battery, due to a possible explosion of the battery.
An input current level equal to the battery AH level may be chosen initially, and reduced gradually if a positive response is detected from the battery.
2) Desulfating with a Transformer and Bridge Rectifier Circuit
To make this simplest yet effective battery desulfator with charger circuit you would just require a suitably rated transformer, and a bridge rectifier. The design not only desulfates a battery, it keeps the new batteries from developing this issue and simultaneously charges them to the desired levels.
At the beginning of this post I have explained how to desulfate using PWM concept, however a deeper research shows that the process of desulfating a battery may not necessarily require a precision PWM circuit, the supply just needs to be oscillating at some given rate, and that's enough to initiate the desulfating process (in most cases)... provided the battery is still within the curing range and is not beyond the reviving state.
So what would you need to make this super simple battery desulfator circuit which will also charge the given battery, and additionally possess the ability to keep the new batteries from developing the sulfation issue?
A suitably rated transformer, a bridge rectifier and an ammeter are all that's needed for the purpose.
The transformer voltage must be rated approximately 25% more than the battery voltage rating, that is for a 12V battery a 15 to 16V supply may be used across the battery terminals.
The current can be approximately equal to the Ah rating of the battery for those which need to be revived and are badly sulfated, for the good batteries the charging current could be around 1/10th or 2/10th of their Ah rating. The bridge rectifier must be rated according to the specified or calculated charging levels.
Desulfator Schematic using Bridge Rectifier
How Bridge Rectifier Operates as a Desulfator
The diagram above shows the bare minimum requirement for the proposed battery desulfator with charger circuit.
We can see the most standard or rather crude AC to DC power supply set up, where the transformer steps down the mains voltage to 15V AC for the specified 12V battery.
Before it can reach the battery terminals, the 15V AC goes through the rectification process through the attached bridge rectifier module and gets converted into a full-wave 15V DC.
With a 220V mains input, the frequency before the bridge would be 50Hz (standard grid spec), and after rectification this is supposed to become double that is at 100Hz. For a 110V AC input this would be around 120Hz.
This happens because the bridge network inverts the lower half cycles of the stepped down AC and combines it with the upper half cycles, to finally produce a 100Hz or 120 Hz pulsating DC.
It is this pulsating DC which becomes responsible for shaking-up or knocking down the sulfate deposits on the internal plates of the particular battery.
For a good battery this 100 Hz pulsed charging supply ensures that the sulfation ceases to occur on the first place and thus helps to keep the plates relatively free from this issue.
You can also see an ammeter connected in series with the supply input, it provides a direct indication of he current consumption by the battery and provides a "LIVE update" of the charging procedure, and whether or not anything positive might be happening.
For good batteries this will provide the start to finish info regarding the charging process, that is initially the needle of the meter will indicate the specified charging rate by the battery and may be gradually expected to drop down to the zero mark, and that's when the charging supply needs to be disconnected.
A more sophisticated approach can be employed for enabling an automatic cut-off once the battery is fully charge by employing an opamp based automatic battery full charge cut off circuit (the second diagram).
3) Using High Voltage Pulse
The configuration detailed below provides the most up-to-date methods of desulfating lead-acid batteries. It is a circuit which routinely supplies quick yet intense pulses to the battery, while discharging the battery marginally between the pulses.
This technique, as much as recognized right now, is the best way to knock of undesirable build up of sulphate crystals and to bring back the battery plates into a good condition.
Because the voltage necessary for the high voltage pulses comes from the battery itself (this might appear a little bizarre initially, however the discharge of the battery is likewise a part of this technique), it is advised to hook up a charger in parallel with the battery and desulfator once the battery has not much capacity remaining.
Pulse generator
It could be noticed in the circuit diagram that the parts needed for the desulphator tend to be extremely humble. The circuit consists of a couple of stages: a high voltage generator constructed using IC1, IC2d and T1, that generates the charging pulses, and an indicator circuit which involves not more than 3 op amps (IC2a, b, c) and three LEDs, that indicate exactly what condition the battery is in.
Let’s go through the pulse generator initially. Just like the other parts of the circuit, its supply voltage is obtained from the battery itself through K1. Although we’re discussing the supply voltage, this must have a pretty consistent voltage and should be devoid of any spikes (except those produced by the circuit itself).
Inductor L1 works like a suppressor, and is included in order to eliminate undesirable voltage spikes, along with C2 and C3 which work like smoothing capacitors.
LED D1 illuminates as soon as the supply voltage is switched ON. To proceed with the pulse generator, IC1 (a 4047) produces a square wave having a frequency of 1 kHz and a duty cycle which typically is 50 PERCENT. When the Q output of IC1 turns high, FET T1 switches ON. This results in a (discharge) current to move through the battery by means of L2, that boosts linearly until the voltage across R4 is approximately 0.35 V; the current can now be around 1 A.
At this instant comparator IC2d changes state, triggering IC1 to be reset and T1 to become switched off. The stashed magnetic energy inside L2 now gets converted to a voltage spike, which is inflicted to the battery through D3. How big the spike is can be determined by the condition of the battery.
If the battery is in a decent condition and its internal resistance is rather small, in that case the spike voltage level may also be reduced (under 15 V). In case the battery has a high internal resistance then the peak level of the spike could be as huge as 50 V. Its highest magnitude will be restricted and equal to the value of the two series connected zener diodes, D4 and D5.
LED Indicators
Considering that the health of the battery could be dependent on how big the charging pulses are, we have included a straightforward LED circuit which indicates the optimum value of the pulses. The 3 comparators IC2a-c evaluate the peak value inside C4 and changeover at voltages of 15, 20 and 30 V correspondingly.
Therefore in case the battery is in a reasonably good shape, the green LED (D8) illuminates, with a under-performing battery, the yellow LED (D9) lights up, and with an incredibly bad battery the red LED (D10) glows.
We have an information that needs to be pointed out regarding the indicator circuit: in order to prevent all three LEDs from illuminating simultaneously in response to a high peak voltage, they are attached in parallel to a single common series resistor (R9).
Since the red LED carries a smaller voltage drop compared to yellow LED, they may in no way illuminate together. But the yellow and green LEDs have got a identical voltage drop, so a similar technique will not do the job here, which explains why the green LED comes with an normal diode (D7), hooked up in series with it.
You will find three alternative methods through which the desulfator may be used. The first is to apply it within an existing system (inside a car as an example) to avoid sulphation from taking place inside a battery having minimum sulphation.
The advanced desulfator circuit is built-in with the system by hooking it up straight to the battery using shortest possible cabling. Because the circuit could be kept connected forever, absolutely nothing more needs to be done.
The current consumption is approximately 20 mA, therefore the battery might discharge in case it is not charged up from time to time. Recovery of batteries which have previously sulphated can be carried out in a couple of techniques. The first method would be to charge the battery, eliminate the charger and after that hook up the desulfator circuit.
Since the power for the charging pulses is derived directly from the battery itself, it is going to gradually discharge. This technique needs to be observed carefully because a completely discharged battery must be recharged quickly.
Most likely in real life many charge/discharge cycles will probably be necessary before a terribly sulphated battery could be restored to life. Since the approach described above needs a great deal of attention and has a danger that the battery could be left in a discharged condition unnecessarily (which can be extremely harmful to a lead acid battery!), another method can be perhaps much better.
The battery is coupled to the desulfator circuit, using a trickle charger hooked up in parallel. This implies, no chargers must be integrated that supply a current of 7 A or higher, yet one that provides a optimum of 1 or 2 A. This could be left coupled to the battery endlessly with no issues.
4) Using High Amplitude Pulsed Current from 555 Boost Circuit
We are not going to offer you a solution that will magically solve all the problems with lead batteries. However, the battery desulfator that we will describe in the following lines has proven its effectiveness, mainly in the United States for now, and the measurements we have been able to make on our model have been very promising. As it costs less than twenty euros, which is negligible compared to the price of a new high-quality battery, why not try it out and see for yourself?
Understanding Battery Chemistry
As you may know, a lead-acid battery involves a chemical reaction that can be written as follows during the discharge process:
Pb + 2H2SO4 + PbO2 -> PbSO4 + 2H2O + PbSO4
In other words, the porous lead of one electrode and the porous lead dioxide of the other are transformed, in contact with sulfuric acid, into lead sulfate and water.
Conversely, during charging, the chemical reaction that occurs is as follows:
PbSO4 + 2H2O + PbSO4 -> Pb + 2H2SO4 + PbO2
In other words, lead sulfate and water are transformed, under the effect of electric current, into lead, lead dioxide, and sulfuric acid.
The reaction is theoretically perfectly reversible, and that is why a battery of this type can be charged and discharged many times.
Unfortunately, over time and especially due to incomplete or poorly done recharges, the "reverse" reaction, i.e., the one that transforms lead sulfate into lead, is incomplete and leaves lead sulfate present on the surface of the battery electrodes or plates.
The phenomenon is unfortunately cumulative because, as this lead sulfate is a poor conductor, it tends to thicken where it has started to deposit, which only worsens the problem.
When the sulfation of a battery has reached a sufficient level, no traditional recharge process can overcome it.
Indeed, due to the poor conductivity of lead sulfate, the internal resistance of the battery increases, reducing its charging current and therefore the effectiveness of the charging chemical reaction, leaving even more lead sulfate present on the electrodes.
The resistance of the battery eventually becomes so high that it cannot hold a charge, meaning it can no longer supply significant current due to its excessively high internal resistance.
The Working Concept
This phenomenon has been known for a long time, and there is a chemical process that can be used to eliminate lead sulfate from a battery before it's too late.
However, it's delicate to implement and relatively dangerous due to the chemicals involved. In fact, the battery must be emptied of its electrolyte (corrosive!) to fill it with the cleaning product (also corrosive), and once this operation is complete, the battery must be refilled with fresh electrolyte.
The approach we propose is different and comes from various studies conducted in the United States on the influence of high-amplitude pulsed currents applied to a lead-acid battery.
According to these studies, and provided that very brief but high-amplitude impulses are applied to the battery, the lead sulfate crystals would gradually be broken down by the resulting ionic agitation occurring at the level of the plates and electrolyte of the battery.
This phenomenon is very slow, but since it can be achieved by simple electrical means, this process doesn't pose any particular problems as no manipulation is necessary on the battery being treated.
Circuit Description
The diagram that we propose is widespread on the internet on the other side of the Atlantic and, as far as we could verify, is attributed to Alastair Ocup. As you can see from in the following figure, it is relatively simple and has many similarities with a boost-type switching power supply.
IC, which is nothing other than a classic 555, is configured as an astable oscillator operating at a frequency of around kHz. It produces very short duration pulses on its output available at pin 3.
When the level of these pulses blocks T1, capacitor C1 charges to the value of the battery voltage via inductor L2.
When T1 is made conductive, which only lasts for a brief moment due to the duty cycle of the pulses produced by IC1, capacitor C1 discharges abruptly across T1 and L1 since it is almost short-circuited by these components.
As soon as T1 is blocked again, the current generated by this discharge cannot abruptly cancel due to the presence of inductor L1. It is therefore sent to the battery via diode D2.
If capacitor C1 is of good quality and if the connection between the circuit and the battery is short and made of a suitable diameter wire, a current peak of the order of 5 to 10A can be obtained with a moderately sulfated battery.
Given the operating frequency of the 555 and the duty cycle of the signals it produces, the circuit's consumption remains relatively low and does not exceed an average value of 40mA
I just build it, but not work and then checked using an oscilloscope nothing pulse or voltage spike Yo the battery.
Adivice me, give solving about this problem.
sir, i want use led for pulse show in this circuit where i connect please help
connect it from pin#3 to ground through a 1K resistor, but the LED will appear continuously lit with any frequency higher than 4Hz
Hi swagatam please i need your help i have a 12v battery@200A and they are 4 in number connected in parallel and i want to make a charger for it, a charger that provide at least 80A for the battery connected in parallel please can you give me pulse width charger circuit with cut off that can handle such high current thanks
Hi Faith, the 80 amp is supposd to come from the transformer of the charger power supply….you can use any relay based automatic charger posted in this website and attach a 14V 100 amp power supply to its input for achieving the required results.
PWM is not required for this
Please can u give me the link to relay base automatic charger
you can try the following
https://www.homemade-circuits.com/2011/12/high-current-10-to-20-amp-automatic.html
can i use irf640 instead of irf540…..or is it work without toroid coils which are arranged in order to make hi pluses.. that is 1000uH and 200uH
torroid coil is not necessary….i am not sure about IRF640, if its current/voltage specs are compatible then it can be used
Can we use this circuit for sealed lead acid battery 6 volts please reply
yes can be tried…
cause mosfet need at least 5v to operate normally.
best regrads
IC 555 will produce a voltage that's exactly equal to the supply voltage, so in the above case the output will be 15V at pin3…not an issue for the mosfet.
hi mr swagatam,i hope you are good
i suggest to add a simple mosfet driver using a transistor cause 555 output voltage is weak and thus will overheat the mosfet,i tried before to connect 555 output to mosfet gate with a resistor and mosfet gets hot.
Hi Hisham, I am good thanks,
555 IC has an output that's more powerful than most ICs, however mosfets never require a powerful signal to operate, they just need a voltage above 9V for operating optimally.
You can try reducing the gate resistor to 10 ohms and check the response….or may be the load you have connected could be above the mosfet range
Interesting circuit. I had a thought, perhaps this could be combined with adding a very small (<3ml) of acid to each cell technique for unmucking dead SLAs typically run to death in UPSs.
If they are at 0.0V I doubt any technique will work but its the ones which have good voltage but next to no capacity that could be salvageable.
thanks for updating this info, appreciate it!
Thanks for circuit skema
is there any inductor on the above schematic ????
which simulator i can use to make this circuit and can have a dead battery in it for charging?
if you plz don't mind…can you plz send me the whole process from the begining till the battery desulphation.. what all the pins are doing … plz .. i will be gratefull to you.
simulation is not required, just procure the parts and the build the circuit, the circuit is explained in the articles itself…
Good day to you sir.
Thank you for sharing all the great work.
A few questions about this circuit :
1. What is the 5k POT for ? & how to adjust it ?
2. Does the IRF 540 need a heat sink ?
3. The negative of charger is directly connected to IC Pin #1 ?
4. How to connect a LED to this circuit, that illuminate when connect to battery ?
5. Any harm if connect to the battery permanently ?
Thanks a lot in advance .
Good day Alaa,
1) 5K is for playing with the output pulse width, which might in turn help to implement a optimal desulfating effect….it could be a matter of some trial and error and dependant on the connected battery condition. however it's not so crucial, you can keep it at the center to begin with
2) Normally it shouldn't require a heatsink, however you can test it practically by touching it, to be on a safer side..
3) yes the negative of the charger needs toeb connected to the pin#1 line of the IC
4) charging indication might not be possible, however an ammeter may be connected in series with the battery positive to get a direct reading regarding the batt response to the charging procedure.
5) yes if the battery begins responding and desulfating…an ammeter can be used for monitoring the same as explained in the above point
Thanks Sachin,
shorting would be advisable only if the battery has sufficient charge on it, unless it's charged fully, shorting won't induce any effect on the plates.
The pulse charger explained in the above article is the ultimate way of dealing with this mess, if the battery responds and wakes up to the pulsed charging only then the shorting of the terminals can be tried, however as shown in the video a high amp resistive load would be more appropriate than shorting since here we don't have to worry about the delay period in ms
Sir, I'm planning to add this circuit on my existing 72v ebike charger. It has 6 pcs.12v 20ah battery connected in series. Would it be possible? What ic regulator should I use for LM555's supply voltage? And what mosfet would you recommend?
Hi Jusi, yes you can try it, just make sure to disconnect the battery positive from the shown point and connect it with the +72V supply……..and connect the positive of the circuit with the positive of last 12V battery in the series which has its negative connected with the bike's ground or the bike's negative….
the negative of the circuit can be joined with this ground that is the common ground line.
Thanks Mikel,
changing 1nF to 1uF will reduce the frequency or the pulse rate, but that will not affect the results, so it's OK.
the mosfet and the supply voltage are also OK, but the current input must be well over 20 amps for desulfating a 100AH battery, so make sure the supply current is at this level.
Hi Mikel,
you can connect an LED across pin3 and ground with a series 1K resistor but it will appear continuously glowing due to high frequency pulses from the IC
Hi swagatam! What is the ideal mosfet for a below 20amp battery?
IRF540 is the ideal mosfet as shown in the diagram
Hi swagatam! Is there a need to change some parts of the circuit if my battery is ranging 7 to 14 amp?
Hi Josue,
no changes would be required for your mentioned application.
can we ad two LEDs to show it is charging and one for it is charged?
I've built the first circuit and when i connect the battery the coil heats up and smokes
please try the above circuit without the coil, the TIP122 will need to be upgraded if your battery AH is higher than 20AH
my battery is 80 AH
Can I use IRF540N instead of IRF540
IRF540N will do and will work for an 80AH battery
Hi,
I started building your old circuit and only realized you have changed them ,but I have bought parts for the old diagram,so can I build the circuit without the inductor with the TIP122 ,or should I Change it IRF540.
Hi, I changed the circuit a long time ago may be a half year ago, it's strange you are building it now.
I would recommend you to make the above shown design instead of the earlier one since adding a coil will not make much of a difference.
Hi Mr. Swagatam, newbee here.
So I've finished assembling the circuit, how to tell that it's working before I start attaching it to the battery? I mean is there some type of indication there or do i've to measure anything first?
thank you.
Hi Imanul,
There's no circuit which can guarantee a perfect desulfation in dead batteries, so you can only hope that this circuit produces the intended results as it's designed as per the standard recommended specifications.
Use the circuit for about 4 hours and then check the battery with an appropriate load, if the charge sustains for an appreciable amount of time you can assume it to be revived, otherwise you may repeat the procedure with some change in the PWM frequency and/or the input current to the circuit and check the response in a similar manner.
…please change the 1n caapcitor with a 10uF capacitor.
connect an LEd across pin3 and ground via a 1K resistor.
When switched ON this LED must flash rapidly indicating a proper functioning of the circuit, changing the pot would change the flash rate on this LEd
you can keep the new capacitor connected and use the circuit for the required purpose, it won't make any difference in the performance.
Is it possible to desulphate my 6v,5ah sealed lead acid battery by this ckt.
yes it's possible
How it to be possible?what changes in the ckt for 6v,5ah sla battery desulphating.and how much time taken to desulphate.
use 10V supply with 3 amp current,
use TIP122 instead of the mosfet
time is not known……. also the result may not be positive, will depend on how much your battery may be recoverable.
Thanks for your information.tell me the Pin connections of TIP122 while using instead of mosfet in this ckt.
pls check its datasheet
thank you I already done it just downloaded the ic pin out then I know the number 1 leg is the ground.
thank you again for your fast response and attention.
hi
I just realise in the circuit there is no ground to the circuit?
if we use power supply to connect to this circuit the plus 15V pole goes to the battery and the circuit where then the negative pole goes?
I know if I use coil and transistor I have to connect the negative pole to emitter but on mos fet not sure looks like this one joint missing from the circuit
could you please correct me if I am wrong?
The line connected with pin#1 of the IC is the negative line and must be connected with the power supply negative.
So Avenger is saying that there is no coming back from hard crystalline PbSO4 .
OUCH!
One should have all batteries under full time trickle charge.
Avenger ,…. which one of Swagatam's designs did you use for your charger?
Carl
Lead Lead Sulfate PbSO4 is part of battery charge discharge cycle. The structural form of PbSo4 makes the difference. While amorphous PbSo4 is reversible while hard crystalline PbSO4 is irreversible and inactive. Shallow cycle batteries never have to be discharged under 12.5 volts. If this happens an immediate charge will consume and transform PbSO4 in to Pb, H2O, PbO2 and H2So4. If let staying there for sometime the PbSO4 crystallize and turns inactive. To make a long story short if battery isn’t in use immediately use Float charging with a battery trickle. Harbor freight tools sell a battery trickle (Floater) for $9.99, which I bought on sale for $6.0. The manufacturer 13.2Volts was only a promise, but replacing VR1 with a 100-Ohm trim pot, I can adjust the voltage from 12.6V to 14.25V. I set it at 13.25V but this is only the first aid. What you need is EQUALIZE the BATTERY; this can be done at 14.5V for some hours. During this process the strong cells start boiling but the weakest cells continue charging. This can be done with a battery tender. I bought one from Wal-Mart connected to my VW Touareg and the next day the relay was chattering ON / OF non-stop. Measured Voltage a found 14.85 Volts. The electronic system of the car was fighting hard against this stupid tender. I solved the problem building up my Battery Tender with precision voltage Window 14.5V stop charging and 12.6V restart charging giving the battery a chance to rest, RELAX. Charging a discharged battery you have to deal with Bulk Charge Current Density that depends from electrode surface and is expressed on mA / Cm2. If a have to deal with an accidentally fully discharged battery I use my Automatic Smart Battery Charger, with Equalizing and reconditioning features.
how can i indigate this is working correctly irf 540 get heat?
Hello Swagatam,
I would like to build a hi/lo adjustable relay/contactor.
Say ….12v on 13.5 off
I could then put it in series with any charger.
It would be great for maintenance and prevent over charging.
A variant of this could also kick in a discharge cycle.
This would be good for desulfating.
Do you have a design lik this?
Yours
Carl
Hello Carl,
Please see the last diagram in the following link, it'll fit your need well:
https://www.homemade-circuits.com/2011/12/how-to-make-simple-low-battery-voltage.html
The second relay shown is not relevant, you may remove it.
Hi Swagatam
Since I was focusing only on the mosfet so I didn't gave you the details of the other sections.
As mentioned earlier, one cycle consists of mainly 3 steps + 1 step to monitor battery voltage. Each step is controlled by a 555 and another 555 is controlling all these 4 ICs (the entire cycle). If you want to have a look at the circuit, here it is.
https://dl.dropboxusercontent.com/u/20969135/Desulfator%204-stage.gif
I am sorry, that is maximum available resolution of the picture.
Now, I repeat my question in other way. If the mosfet can be driven directly by the 555, why the author deployed 0.8A transistors to drive the mosfet. You can find them at the top-right corner. I haven't linked the website as per your general instruction however, if you want to see the circuit description I can send you the link.
Hi Abu-afss,
It could be for allowing the mosfet to conduct and restrict correctly, especially the use of the push-pull (PNP/NPN) stage which ensures safe charge/discharge of the internal cap of the mosfet, because as we all know how sensitive these mosfets can be at times.
Hi Swagatam 🙂
One complete cycle includes 3 steps:
1) 15 sec pulse charging
2) 1 sec delay for settling
3) 100ms shorting battery terminals
I am just curious about the driving of the mosfet as I asked in my previous post.
Hi Abu-Hafss 🙂 how are these three steps implemented because i can see only one active input from the IC 555.
I wanted to know the relevance of the transistor stages for answering your question correctly.
Normally we know that a mosfet gate can be integrated with any IC output may it be a 555, a cmos or a opamp, as long as the voltage is below 15V
Hi Swagatam
I came across a desulfator circuit which, apart from the regular desulfation process, also shorts momentarily battery terminals as shown here:
https://dl.dropboxusercontent.com/u/20969135/Desulfation.gif
I want to know, couldn't the signal from the 555 pin#3 be directly fed to the gate of the mosfet (point A) or at point B?
Hi Abu-Hafss,
How does this circuit desulfate…is it by charging and shorting the battery alternately? I could not understand the concept.
Hi Swagatam
I have read some of above posts talking about an inductor L1. Where is that inductor, I can't see it in the circuit or any reference in your article?
By the way, I am working on a trickle charge desulfator. I am considering to integrate a circuit to measure battery's internal resistance (BIR). There are a few BIR measuring circuits on the net but, they need to take occasional measurement manually. Here are two of them:
https://dl.dropboxusercontent.com/u/20969135/internal-resistance-tester-for-batteries-2.jpg
https://dl.dropboxusercontent.com/u/20969135/accutest.jpg
My idea is to have three-LED indication……..the red LED to indicate high resistance, yellow to indicate medium and green for very low resistance. The BIR circuit will operate in parallel with the desulfator circuit. The illumination of the green LED would indicate that the battery has been desulfated, now it is ready to use.
A relay could be used to connect the BIR circuit to the battery periodically to check the status. A latch can be deployed to keep the indicator LED on but, I just cannot sort out how to get the output on LED as the output is just 5-50mV.
Can you please help me in this regard? If required, I can send you the links of the sites to have the description of those circuits.
Hi Abu-Hafss,
In the original design I had used an inductor but later found that it could be avoided and came up with the present design , the inductor related comments that you see were posted with reference to the earlier design
A BIR could be a very useful ad-on.
50mV can be amplified by using a opamp may be. What do you think?
Hi Swagatam
Here is my basic design for LED indication of BIR status. The reference voltage is 12mV.
https://dl.dropboxusercontent.com/u/20969135/BIR%20indicator.gif
But, later I realized that the output is is mVAC. Any suggestions, how to deal this issue?
Hi Abu-Hafss,
I am not able to recollect the previous discussions and the simulation made by me with reference to this diagram, so not able to figure out much about the circuit, if you can point out specific concerns in your diagram then probably I can try suggesting my opinions.
Hi Swagatam
Kindly refer to my post of January 12, 2014. Here is the link for your ready reference.
https://dl.dropboxusercontent.com/u/20969135/accutest.jpg
The battery internal resistance is measured in mVAC. A good battery would show less than 12mVAC. And with higher internal resistance would show more than 12mVAC.
I am just wondering how to compare the fluctuating mVAC with a reference voltage.
Hi Abu-Hafss,
I think it would be a better idea to use a LM3915 IC for detecting the relevant voltage levels because the opamp circuit could become too complex.
Refer to the last diagram in the following article, the mic can be removed and the transistor may be directly fed from the 100k pot output
https://www.homemade-circuits.com/2012/03/how-to-make-vibration-detectormeter.html
please ignore these initial comments, the diagram has been modified and updated differently, so these comments have no relevance with the present diagram.
i am very proude of you . how can i indicate this circuit is working after design
keep a voltmeter attached with the battry, if the voltage increases gradually within 4 hrs means it's working.
Thanks again Swagatam, will update the thread with my results.
btw, I read somewhere (maybe here..) that the high current pulse may burn out shorted cells restoring even batteries that are considered unrepairable.
Hi Sean,
Then that would be an added feature of this design.
Looking forward to your updates…best wishes!
Hi Swagatam
Finally have parts to make the pwm but looking for a hi current supply.
It occurred to me that lead acid batteries will not sink as much current as it starts to get full. Does the circuit take this into consideration ?
When the transistor is on, is it essentially grounding the battery ?
When it is off, is there any ringing without an inductor ?
Sean
Hi Sean,
If the voltage is set at some higher level then that will force the battery to sink the current which in turn will hopefully initiate the desulfation process.
Here you can try with a 15V DC, current may be equal to the AH level of the battery and the pot set to provide short pulses.
When the transistor is ON, it connects the negative of the battery to the negative of the power supply completing the circuit for the battery so that it receives the required charging pulse.
No, there won't be any ringing effect due to the absence of an inductor.
hi Swagatam,
Thanks again for your reply. How do I limit the current ?
I planned on using an old server power supply or rewinding the secondary of a microwave transformer. Won't the circuit try to pull all the current it can unless its limited ?
Sean
Hi Sean,
The circuit will not draw anything above 5mA, as long as the voltage does not exceed 15/16V mark, above this anyway the IC555 would get damaged, so I don't think any current control for the circuit would be required.
Hi Swagatam, I think you mis-understood my question.
With your circuit you recommend limiting the current to the battery initially to 1C. so if I have a 40AH battery, I should limit the pulse current to 40AH. I was asking how I could do this since I don't have a power supply with a current limit. I am thinking of making a power supply by stepping down 240VAC to 15VAC and rectifying it. But this will not be limited. Is there a clever way to control the max current the battery draws ?
Hi Sean,
You can select a transformer rated at around 20 to 30 amps, that will itself take care of the current…actually the current is not a critical value, anything higher than the normal charging method can be employed, and expected to work here.
Thanks for your clarification. I was curious about the use of the inductor (i.e. collapsing magnetic field/pulse, etc).
Anyhow, I will try this circuit out as its simple enough to make. I would like to try to revive some large capacity (100AH) NiMh batteries I have pulsing with high current. I am hoping the technique will lower the internal resistance of the batteries even though the chemistry is different (i.e. they don't sulphate).
I wanted to keep it simple, so I eliminated the inductor part, I hope it works for you….:)
Thank you Sean,
Actually the circuit has gone through many changes since it was first posted, so please ignore the previous comments as those are with reference to the previous diagram which had quite a few flaws.
The present design looks to be easier and viable.
Hi Swagatam, your circuits are incredibly practical. Thanks for sharing and explaining.
I am a bit confused as I read the thread as I saw reference to a 100K pot and L1 inductor but the circuit above for PWM 555 pulser does not show these. What am I missing ?
2.bp.blogspot.com/-L9UBEjJp8XU/UUQLd8oW6YI/AAAAAAAADkk/FlaSh6PwIos/s1600/battery+desulfator+circuit.png
Sean
Thanks!
The negative will go to the rail which is connected to pin#1 of the IC
Hi Swagat,
I need a signal strength meter for direct to home disc alignment at roof.
Can it be made simply at home with transistor and led.
Thanks
Hi Nawnit,
UHF Signal meters are complex devices, not within my reach.
But m not sure if it will be failed for high voltage input. Vl try to make a diagram of switching.
Please comment.
It's difficult to guess how it will do with high or low voltage condition, we can't say without practical testing, let's see…
Thanks Swagat,
Tryed smthing diffrnt with the stablizer that i must share wid u.
There are 5 taps in auto transformer, 1st n 3rd tap has been used as input with a relay control and rest for output wid 2 more relays.
I inspected the 1st relay status at power on, it was making 1st tap as as input for 1 sec then change it to 3rd tap as input, so there was high volt at power on.
I interchanged 1st and 3rd tap input with relay.
Now its working good .
Thanks Swagat,
sorry for one more problem,
I inspected the stablizer, it has 24 volts relays, so i need to operate the "delay on" circuit on 24 volts instead 12 volts.
What modification i need?
Thanks
You will have to use a 24V relay in the circuit, that's all, no other change would be required.
The 24v supply for the circuit can be derived from the stabilizer board itself.
Thanks buddy,
will it work fine upto 4 kw load?
You will have to select the relay appropriately, I think a 30 amp relay would do the job.
Hi Swagatam, I have installed automatic voltage stabliser for home supply,
the only problem is, when it starts, initialy it supply high volts(300 ) for less den 1 sec. den it functions well..
Pls let me know what is the problem n how can i fix it..
Hi Nawnit,
You will need to add a delay ON timer at the output of your stabilizer as shown in the following link, a similar situation has been addressed at the bottom of the article.
https://www.homemade-circuits.com/2013/02/make-this-simple-delay-on-circuit.html
Swagatam:
Very nice, I appreciate your attention to my queries. Best wishes from Guatemala.
Hugo
You are welcome Hugo!
Swagatam:
Swagatam:
Thanks for your reply and recommendation. If working at 555 with 5 volts regulated from 7805, the oscillation frequency is not affected?
Are pleased to greet and congratulate again the excellent circuits published.
Thanks Electronica,
yes it will not be affected.
Swagatam:
Excellent circuit, I'm about to try arm. I'd appreciate if you tell me regularly cnveniente a zener and 100 ohm resistor voltage to the 555 and ensure it does not overheat.
Thank you for your attention
thanks electronica,
the IC can work safely with upto 15V, yet for extra stabilization you may use a 7805 IC for it.
Good day, Swagatam,
I didn't get nF capacitors (not available at the shop I went to), I bought a 1 microF and a 100 microF. If I substitute these into the circuit, how will it affect the output?
Thanks,
Satyam.
Good day Satyam,
The circuit needs to be operated with high frequency so a 1uF or 100uF will not work.
1nf = 0.1uF, so can try other closer values like 0.22uF etc. or any value between 0.01uF to 0.1uF will also do.
oops, correction: 1nF = 0.001uF
better use a 680pF for pin6/2 and 103 or 0.01uF for pin5
Good day,
Thanks for your quick response. I've built the circuit with the components that I described, however I'll keep looking for the correct capacitors. (I got some surface-mounted caps yesterday, but destroyed them trying to install them.)
I suspected that my frequency would be affected. Using f= 1/(0.693 x C x (R1 + 2R2)), the frequency of my circuit would be somewhere around 300 Hz, whereas your design is for 300 kHz. Does that sound about right?
At any rate, I'm using it on a number of car batteries where I suspect sulphation. Will come back & update when I replace the caps, or with results.
Best regards.
Higher frequency would produce better effects according to me, however the pwm pulses would finally decide the optimization rate.