In this article I have explained a simple low dropout LDO, or zero drop solar charger circuit without microcontroller which can be modified in many different ways as per user preference. The circuit does not depend on microcontroller and can be built even by a layman.
What is a Zero Drop Charger
A zero drop solar charger is a device which ensures that the voltage from the solar panel reaches the battery without undergoing any drop in voltage, either due to resistance or semiconductor interference.
The circuit here uses a MOSFET as a switch for ensuring minimum drop in voltage from the attached solar panel.
Moreover the circuit has a distinct advantage over other forms of zero drop charger designs, it does not unnecessarily shunt the panel making sure the panel is allowed to operate at its highest efficiency zone.
So I have explained how these features could be achieved through this novel circuit idea designed by me.
Simplest LDO Circuit
Here's a simplest LDO solar charger example which can be built in minutes, by any interested hobbyist.
These circuits can be effectively used in place of expensive Schottky diodes, for getting an equivalent zero drop transfer of solar energy to the load.
A P channel MOSFET is used as a zero drop LDO switch. The zener diode protects the MOSFET from high solar panel voltages above 20 V. The 1N4148 protects the MOSFET from a reverse solar panel connection.
Thus, this MOSFET LDO becomes fully protected from reverse polarity conditions and also allows the battery to charge without dropping any voltage in the middle.
For an N-channel version you can try the following variant.
Using Op Amps
If you are interested to build a zero drop charger with automatic cut off feature, you can apply this using an op amp is wired as a comparator as shown below.
In this design the non-inverting pin of the IC is positioned as the voltage sensor via a voltage divider stage made by R3 and R4.
Referring to the proposed zero drop voltage regulator charger circuit diagram we see a rather straightforward configuration consisting of an opamp and a mosfet as the main active ingredients.
The inverting pin is as usual rigged as the reference input using R2 and the zener diode.
Assuming the battery to be charged is a 12V battery, the junction between R3 and R4 is calculated such that it produces 14.4V at a certain optimal input voltage level which may be the open circuit voltage of the connected panel.
On applying the solar voltage at the shown input terminals, the mosfet initiates with the help of R1 and allows the entire voltage across its drain lead which finally reaches the R3/R4 junction.
The voltage level is instantly sensed here and if in case it's higher than the set 14.4V, switches ON the opamp output to a high potential.
This action instantly switches OFF the mosfet making sure no further voltage is allowed to reach its drain.
However in the process the voltage now tends to fall below the 14.4V mark across the R3/R4 junction which yet again prompts the opamp output to go low and in turn switch ON the mosfet.
The above switching goes on repeating rapidly which results in a constant 14.4V at the output fed to the battery terminals.
The use of the mosfet ensures an almost zero drop output from the solar panel.
D1/C1 are introduced for maintaining and sustaining a constant supply to the IC supply pins.
Unlike shunt type regulators, here the excess voltage from the solar panel is controlled by switching OFF the panel, which ensures zero loading of the solar panel and allows it to operate at its most efficient conditions, quite like an MPPT situation.
The LDO solar charger circuit without microcontroller can be easily upgraded by adding an auto cut off, and an over current limit features.
Circuit Diagram
NOTE: PLEASE CONNECT THE PIN#7 OF THE IC DIRECTLY WITH THE (+)TERMINAL OF THE SOLAR PANEL OTHERWISE THE CIRCUIT WILL NOT FUNCTION. USE LM321 IF THE SOLAR PANEL VOLTAGE IS HIGHER THAN 18 V.
Parts List
- R1,R2 = 10K
- R3,R4 = use an online potential divider calculator for fixing the required junction voltage
- D2 = 1N4148
- C1 = 10uF/50V
- C2 = 0.22uF
- Z1 = should be much lower than the selected battery over charge level
- IC1 = 741
- Mosfet = as per the battery AH and the solar voltage.
Using N-Channel MOSFET
The proposed low dropout can be also effectively implemented using an N-channel MOSFET. as indicated below:
NOTE: PLEASE CONNECT THE PIN#4 OF THE IC DIRECTLY WITH THE (-)TERMINAL OF THE SOLAR PANEL, OTHERWISE THE CIRCUIT WILL CEASE TO WORK. USE LM321 INSTEAD OF 741 IF THE PANEL OUTPUT IS HIGHER THAN 18 V.
Adding a Current Control Feature
The second diagram above shows how the above the design may be upgraded with a current control feature by simply adding a BC547 transistor stage across the inverting input of the opamp.
R5 can be any low value resistor such as a 100 ohm.
R6 determines the maximum allowable charging current to the battery which may be set by using the formula:
R(Ohms) = 0.6/I, where I is the optimal charging rate (amps) of the connected battery.
Finalized Solar zero drop battery charger circuit:
As per the suggestion of "jrp4d"the above explained designs needed some serious modifications for operating correctly. I have presented the finalized, corrected working designs for the same through the below shown diagrams:
According to "jrp4d":
Hi - I've been messing about with Mosfets (voltage control circuits) and I don't think either circuit will work except where the line in voltage is only a few volts large than the target battery voltage. For anything where the line in is much more than the battery the mosfet will just conduct because the control circuit can't control it.
In both circuits its the same problem, with P-channel the op-amp cant drive the gate high enough to turn it off (as observed by one post) - it just passes the line voltage straight thru to the battery. In the N channel version the op-amp can't drive the gate low enough because its operating at a higher voltage than the -ve line in side.
Both circuits need a driving device operating at the full line in voltage, controlled by the op-amp
The suggestion above looks valid and correct. The simplest way to rectify the above problem is to connect Pin#7 of the opamp IC with the (+) of the solar panel directly. This would instantly solve the issue!
Alternatively the above designs could be modified in the manner shown below for the same:
Using NPN BJT or N-channel mosfet:
In the above figure the NPN power transistor could be a TIP142, or a IRF540 mosfet .....and please Remove D1 as it's simply not required.
Parts List
- R1, R2 = 10 K
- R3, R4 = use an online potential divider calculator for fixing the required junction voltage
- D2 = 1N4148
- C1 = 10 uF / 50 V
- C2 = 0.22 uF
- Z1 = should be much lower than the selected battery over charge level
- IC1 = IC 741
- Lower Transistor = TIP142 or as per the battery Ah and the solar voltage.
Using PNP transistor or P-mosfet
In the above figure, the power transistor could be a TIP147 or a IRF9540 mosfet, the transistor associated with R1 could be a BC557 transistor......and please Remove D1 as it's simply not required.
How to Set up the LDO solar charger circuit
It's very easy.
- Do not connect any supply at the mosfet side.
- Replace the battery with a variable power supply input and adjust it to the charging level of the battery which is supposed to be charged.
- Now carefully adjust the pin2 preset until the LED just shuts off....flick the preset to and fro and check the LED response it should also blink ON/OFF correspondingly, finally adjust the preset to a point where the LeD just shuts off completely....seal the preset.
- Your zero drop solar charger is ready, and set.
You can confirm the above by applying a much higher input voltage at the mosfet side, you'll find the battery side output producing the perfectly regulated voltage level that was previously set by you.
The mosfet in this circuit will only work when the battery has the lowest internal resistance. Otherwise-overheating and failure.
Mosfet does not have time to give heat to the radiator.
I try 2nd circuit (Simplest LDO N-MOS) but when solar panel voltage drop below battery voltage, then current flow back to solar panel. I want to replace schottky diode with your circuit. How could I do?
Please replace the MOSFET with a BJT and try again. Let me how it goes.
Good day Swag, I designed the second to last circuit for solar controller 3years ago, worked perfectly without fans, but recently I designed same circuit but the mosfets blow without fan. Now I must use fan, please what could be wrong.
Hi Seun, are you referring to the following circuit?
https://www.homemade-circuits.com/wp-content/uploads/2013/08/zero-1.png
I guess you used the mosfet in place of the upper power transistor.
As you can see that the upper transistor has only the battery as the load. If your mosfet is correctly rated to handle the battery current then it should not heat up much.
You can try using a BJT instead of a mosfet and check the results because BJTs are more reliable and predictable than mosfets.
Try using a TIP36 and makes sure the base resistor (ground resistor) is adjusted correctly for maximum current delivery.
Please how can I use one circuit of the n-channel MOSFETs below to control 4 DIFFERENT SOLAR system setups, can it supply adequate voltage to the gate?
Can I modify the circuit for 6V battery, how, Sir?
Thanks
Tinu, I did not understand your question…which circuit are you referring to?
Using the second to the last circuit here, can one circuit used to drive 4 MOSFETs sets, single for 4 different solar systems, e.g say 1kw solar system for 4 different inverter power systems.
Also, how can I modify it for 6v battery?
For 4 different solar panels, 4 different op amp circuits would be required, a single circuit cannot be used for controlling 4 solar panel systems.
6V can be used but only R3/R4 will need to be changed accordingly.
Hi Swagatam. It’s Chris ????
I’ve got two solar panels here and both are 150watt panels.
But the problem here is that their voltages don’t match. One has an open circuit voltage of 23.5v(which even rises to 24v most times) the other panel has open circuit voltage of about 21.2v.
Is there a way to connect them both to my solar charge controller so that I can make use of them both to charge my 100Ah solar battery?
Just a suggestion. I was thinking of building your circuit above but with lm324(where I’d make use of two it’s opAmps) for each panel to lower down their their voltages to a common voltage (let’s say 19v or 20v) then connect them in parallel and feed it to the solar charge controller.
Please if you’ve got any other better ideas please help me. Thanks.
Hi Chris,
Surely you can do that! You can build two of the following circuits and connect their outputs in parallel to feed your controller circuit. Make sure to mount the transistor over a very large heatsink.
Thanks for the response.
1) Please what are the values for R1 and Zx that would give Me the required amount of volts I need for this purpose?
Can I replace TiP35 with TIP41c as this former is not available here, but TIP41C is.
R1 will need to be experimented to find which value provides the maximum solar panel output current.
TIP41 cannot be used since the 100 Ah battery would require 10 amp current minimum,and each panel would need to deliver 5 amps each….TIP41C cannot handle 5 amps.
Okay.
1. How about in each Solar panel’s circuit, I connect two TIP41c in parallel(just like MOSFETs in parallel). would it help increase the amount of current each circuit would deliver?
Or can I use MOSFETs in the circuits in place of the the transistors?
You can connect them in parallel, just make sure they are mounted on a common single heatsink, very close to each other.
MOSFET source follower will drop around 5V so that may not be very efficient.
Alright. Mr swag, Thank you so much.
I’d do just that. If I encounter anything else. I’ll be sure to text you.
No problem Chris, all the best to you. Let me know if anything goes wrong.
Hi Swagatam. I’m kinda new to making circuits.
1) I’m confused on how to setup the circuit. You made mention of using a LED to test the circuit. Where am I going to connect the LED?
2) In your above circuit (after the 5th circuit posted in this page), you made mention that pin 4# should be connected directly to the (-ve) of the solar panel(i.e for the NPN mosfet version). My question Is, should we still connect pin7# directly to the (+ve) of the solar panel as well? Or ignore connecting pin7# directly to +ve of the solar panel but ensure we connect pin4# to the -ve of the panel?
Note: this questions are for the NPN mosfet version.
Thanks.
Hi Chris, The set up procedure is explained for the last two circuits. I am sorry, I forgot to show the positions of the LEDs. Actually in the last two circuits the zener diodes connected at pin#6 of the IC 741 must be replaced with LEDs for the required indications. The polarity of the LEDs will be exactly opposite to the shown polarities of the zener diodes.
2) For the 4rth and 5th circuits using N channel mosfets, the pin#4 can be connected directly to solar negative terminal but nothing needs to be done to the pin#7 because the entire positive line is already associated with the solar panel positive terminal.
Thanks Swags for the quick response. Here’s another question.
I intend building the 5th circuit, but for now i don’t need the current control feature.
1) Could i still build the circuit without including the bc547, then ignore Rx and link it directly?
2) There’s this Shining diode connected to a 1K resistor in the 5th circuit beside the IRF540 mosfet. Is it necessary to include it?
*And if yes, what’s the number of the diode?
* if no, can i just remove both the shining diode and its companion(the 1K resistor)????
Thanks.
You are welcome Chris!
1) Yes if you don’t the want the current limiting feature you can remove the BC547 and RX network from the design. The RX can be replaced with a directly link.
2) The shining diode is actually an LED. You can remove that if you don’t want any kind of indication feature in the design.
Okay Swags.
You said in the last two circuits, its mandatory to replace the zener diode with a LED. I actually want to build the 5th circuit in this page, but the 5th circuit has a zener diode, Z2 at pin 6#. Must i replace the zener in the 5th circuit with a LED too..
If yes, please tell me.
If no, Please what’s the value of the zener diode.
Thanks
Actually, an LED connected at the gate of a MOSFET will not illuminate due to the high impedance of the MOSFET gate, so LED cannot be used in series with a MOSFET gate. You can put a zener diode instead as indicated in the diagram. The LED indication can be put between pin6 of the IC and the ground line, if required.
The value of the of the zener can be a 4.7V zener
Thank you so much Swags.
I really appreciate the quick responses here. When I’m done building this circuit, I’ll let you know.
No problem Chris, let me know if have any further questions.
Hi swag. Its me again????.
My solar panel’s open circuit voltage is 21.2v, and in your instructions, you said we shouldn’t use ic 741 but rather lm321. Stores here don’t have lm321. So please, what other alternative ic can i use?
Can i use lm324? Or maybe lm358?
Sure Chris, you can use LM358 or LM324 op amps for your application, instead of 741
Good day Sir, I noticed some installed Solar panels of about 1.7kw for one 200ah battery, releasing about 84amps to the battery, is it advisable,
Also, what are the advantages and disadvantages of this in the tropical region with high solar irradiance now. Thanks.
Hi Seun, applying 84 amps to a 200 Ah lead acid battery will ruin the battery soon. The correct amount of current which could be applied continuously to a 200 Ah battery is 20 amps….which may take more than 10 hours for the battery to get fully charged. On the other hand if a faster charging is required, then the 84 amp may be applied to the battery until it reaches its 60% charge value, and then the current could be reduced to 20 amps, until fully charged
Thanks Sir for your reply,
Please which n-channel MOSFETs will you recommend, but even with 12pcs of mosfets, heatsink and fan, the MOSFET got damage.
For controlling 20 amp charging current a single IRFP2907 should be quite enough
I discovered that mppt controller also has fan. Sir, if the fan in it stops,what will happen to the mppt.
Please Sir, how can a circuit sense this, and stop the charger.
Your MPPT should have an internal thermal overload protection which will shut off the charger if the circuit overheats. If overheat protection is not there in your MPPT you can add your own overheat cut off circuit using the following circuit:
https://www.homemade-circuits.com/wp-content/uploads/2019/08/LM35-Temperature-relay-controller-circuit.jpg
Sir, can a mppt charge controller intelligently charge the 200ah battery with 84amps?
It will depend on the MPPT specifications. If it is designed to sense and control the 84 amp current in steps, then it can be used.
Thanks Sir, Swag, how will I know Mppt that can handle this stepwise control?
Seun, If you want to buy an MPPT then you will have to specify the step control feature to the dealer, he will help you out. Thee should be LED indicators on the MPPT which will tell you about the changeovers.
Good day Swag, please I don’t know what happened to my battery bought 2weeks ago.
Initially, with my 900w panels I set to control at 14.5v, and while on load it holds at that for long.
But now on same loads it drops to 14.1v even at peak sunshine. Please what could be wrong?
Hi Seun, according to me supplying 14.5V to a 12V lead acid battery for long hours can be harmful for the battery. Ideally you must have an auto cut off at 14.3V. If you intend to charge the battery continuously without cut off then you can keep the full charge level restricted to 14.1 V.
It seems your battery has degraded a bit and therefore it is unable to deliver its full capacity.
OK Sir, thanks. At this damage, is it safe to put it at 14.1v or lesser. If it can salvage the damage.
Yes, 14.1 V or 14V continuous charging will not harm a lead acid battery, since its full charge cut-off level is 14.3V. No, once the battery is degraded there’s no way to revive it….the low voltage will not revive the battery condition.
Thanks for this circuit, I use it to control about 60amps current from my panels, I used heatsink and fan to prevent the mosfets from getting hot that could lead to damage.
Please how can I safeguard it from sudden failure of the fan, because if the fan stops it damages the mosfets.
Th only way to protect the mosfet is by reducing their dissipation by adding more number of mosfets in parallel and by installing them over an appropriately dimensioned heatsink.
Hi, Thanks for all the information.
Just for my understanding
Why do you claim at the beginning of this article:
“These circuits can be effectively used in place of expensive Schottky diodes, for getting an equivalent zero drop transfer of solar energy to the load.”
The circuit consists of 3 active components an a resistor. A Schottky diode costs about 0,30€ up to 1,50€ depending on power. I do find the same price range for the MOSFET.
Hi, Actually, the price is with reference to the high current schottky diodes in the range of 50 to 100 amps. For example a typical 100 amp schottky diode may cost 2 times more than a 100 amp MOSFET such as IRF3205, according to my knowledge.
OK, I understand. Thanks alot.
I am looking into a design which should be imune to rapid changing particular shading.
My idea is to have each cell cut into 40 segments and souldering those in serial. That would make Vmax of about 20 Volt and Imax less than 1 Ampere per 1 cell panel. I expect, that there would be no overheat protection needed for partical shading of a single segment in one of those panels. Panelsize would be around 170×170 mm. Alot of those panels could be in parallel with each a Schottky SMD diode 40V 1,5A in flow to protect from other such panels.
Now I am looking into mppt or other method to charge a lifepo4 battary bank with such an array.
Any ideas?
P.S. I expect, that normal MPPT would be to slow to react to shading changes with frequencies of 1/2 Hz or more. So I thought that some lightsensor to measure bright sunlight, partly covered or full covered sky and adjusting to it would be a way.
Sorry I am not sure how a light sensor can be connected with an MPPT for correcting the issue?
I have a few MPPt circuits posted in this blog, you can find it in the following link.
https://www.homemade-circuits.com/mppt-circuit-using-pic16f88-with-3/
Please Sir, I need a circuit which activate relay when it is sunny but turns off on a cool day.
Should it be a temperature triggered circuit, or a light triggered??
Maybe high current or voltage sense from solar panel
It can be very easily done through an opamp comparator circuit. Clamp pin2 of a 741 opamp with a zener/resistor, and put a preset on pin3 of the opamp. The output pin6 can be configured with a relay driver through a LED at the transistor base. The whole system can be connected to a solar panel.
Good day Sir, I bought 2 same wattage and type panels of 2 different brands but one charges faster and better than despite same rating and price.
What factors could be responsible?
Hello Seun, it is the current output that may be higher or optimum in one of the solar panels compared to the other, which may be causing the difference.
Good day Swag, please what is the value of z2, it’s function, and why is its direction for pnp and npn different. Thanks
Hi Seun, the function of Z2 is to block the leakage voltage from the op amp output from reaching the transistor base. Its value can be 3 V. You can replace it with an LED also for the same purpose. For PNP the current flows from emitter to base, whereas for NPN current flows from base to emitter, that is why the zeners are positioned differently for the two versions.
Good day Swag, please what is best discharge current for 100ah tubular battery.
2. Between 100ah tubular and 150ah agm battery, better?
Thanks Sir
Hi Seun, for all 100Ah batteries except Li-ion or Lipo, the safest charge discharge rate is normally 10 Ah.
2) tubular batteries are better than agm batteries
Yes Sir, tubular are better but comparing the safe discharge current of 10A of tubular and 15A for agm from the analogy. Which is better in this regard.
Ideally both the batteries must be charged/discharged at 1/10th value of their Ah rating.
But how first circuit can be considered as zero drop? There is drop from 18V on PV to 12V on zener diod. So there is 5V drop, when PV gives full 18V.
The output will be 18V only, the 12V zener is used only for protecting the FET gate from over voltage
Thank you for quick answear. Sorry for trouble.
Good day Sir, I am trying to design zero ldo controller for 48v system, I tried to connect the 48v solar supply to control circuit of 12v, but couldn’t control it.
So I want to design 48v design, please what are the modifications
Hi Seun, you can try any of the following circuits:
https://www.homemade-circuits.com/low-dropout-5v-12v-regulator-circuits-using-transistors/
Change the zener to 48 V zener for getting 48V output, or set it as per whatever value you want to get at the output.
Good day Sir, please will capacitor across the battery terminals have any good effect, if yes what value.
Hi Seun, Yes it will have a good effect, the larger the better, in general you can put a 2200uF, or a maximum of 4700uF
Thanks Sir, for knowledge reason, what’s the effect of value more than 4700uf
Higher values will only help to improve the response!! But it is absolutely not necessary because the improvement is quite minimal….it may slightly help to charge the battery faster
Thanks for this article, it is working well. The issue I have is that my panel’s open circuit voltage is 22.5v for 12v system. At peak sunlight, the voltage overshoot the 14.1 set value, but with panel with 18v open circuit, it is well controlled.
Please how can I handle the first panel and the last design
Seun, Please mention which circuit you are referring to, it is not possible to remember the older thread conversation?
I used the last circuit as a topology for N channel MOSFET
OK, then definitely your circuit has problems, because the transistor will block the excess voltage regardless of whether the solar panel voltage is 18V or 22V. You can try replacing the transistor base zener with an LED which will indicate the correct working of the op amp during over voltages above the et value….otherwise your transistor might have gone faulty…
Hi, can you please help me. I would like a simple circuit that goes between the micro miniature solar strip ( taken from an old not functioning calculator ) and rechargeable batteries ( 1.5 x 4 v ) , so as to avoid current flowing back from the batteries to the solar strip and burning it. They do it on the calculator, so it must be very simple and cheap circuit…… a simple diode will do ? Thanks for helping me out. Cheers. Jack
Hi, you can use a suitably rated schottky diode for blocking the reverse battery flow
Please how can I prevent back flow into solar at night
Use the LDO technique explained in the above article.
OK sir, thanks. How can I choose a good N-MOSFET with minimal losses.
Seun, it will depend on the wattage of the load, the MOSFET maximum power dissipation rating should be at least 50% of the load wattage
OK sir, thanks. What value of mov can I use to protect the solar system
MOVs are not designed for solar panels, it is designed for mains AC applications.
OK sir, how can I protect this controller from surge. Thanks
Seun, Solar panel will not produce surge, it will produce peak voltage periods during peak sunlight, for that you will need a constant voltage regulator. Please specify your exact load requirement and panel specifications.
I meant surge from lightning .
For lightening you must have an earthed rod installed near the panel. And also use industrial based MOV such as below:
https://www.homemade-circuits.com/high-power-industrial-surge-suppressor/
Thanks sir, I tried the simplest ldo circuit of n channel, I also added LED indicator. But the issues are:
1. The LED is still on at night despite no sun, I observed the positive line is linked between the panel and battery, so I think that may be the cause
2. I don’t know if my n MOSFET has no internal diode, because there is battery drain even when I remove gate voltage supply at night. I have looked into the circuit to know how to circumvent it, no solution. I only disconnect the solar input at night to prevent this occurrence. Please help out
Seun, that may be surely happening due to the body diode of the MOSFET, otherwise there can be no path for the battery voltage to drain through the solar panel.
Please replace the MOSFET with a BJT and check the response again. You can try a TIP122 for the experimentation.
Thanks so much sir, it is working well with MOSFET. Please how can you help with incorporation of voltage follower, that will help to a automatically adjust instead of using the preset.
I noticed during cool days, the preset needed to be increased which makes it charge faster but needed to readjust the preset not to overcharge the battery.
Thanks sir.
Seun, which circuit are you referring to??
I used the last circuit as a topology for N channel MOSFET
The preset should not be changed once it is set, if you change the preset setting then the cut off level will change and that may not be good for the battery. In winter the current from the panel may drop which may cause slower charging, and the only way to correct this is by adding more panels in parallel, or alternatively you can use a buck converter which will convert excess voltage to current
Good day sir, well done. I have 5panels 2 150w and 3 100w. Please how can I combine them for my 24v system using the design above, which is not mppt. Thanks
Seun, if their voltage specs are same then you can join them in parallel
Hello – I have a small 6-9 VDC generator charging a 6 VDC lead acid battery C20 capacity: 50 Ah. Maximum charge rate is 15 amps. This is a positive ground system. Would you recommend any changes to the “simplest LDO, zero drop solar charger circuit” above using the low side IRF540 mosfet in a simple charging circuit? Thanks! Steve
Hi, No changes would be required in the IRf540 design
Thank you! Steve
Please how can I use solar panels and inverter without battery. Thanks Swagatam for your usual assistance.
yes you can, as long as the solar panel specs matches the required inverter specs
How sir, I have 720w panels.
The voltage and current specs of the panel must be approximately as per the inverter DC input specs.
Sir can i use the circuit uve made using n mosfet 1 diode and 1k and 12vzener diode? Ihave 100ah battery and 150w 19v solar panel is this ok?
Yes you can use it.
Hello sir, please how can I add an indicator to show sun is on and off
Thanks Swag.
You can add an LED in series with a zener diode and resistor. The zener cut off voltage will decide at what solar level the LED is supposed to switch OFF
Thanks sir, I meant the led will light when sun comes up in the morning and goes off at night when there is no more sun.
Yes the suggested idea will do exactly the same.
Please sir, what type of zener diode and resistor can I use for 24v system and 12v system. Thanks sir, Swagatam
Adeyemi, for all systems the gate zener will be 12 V
Hello Sir, can you help me again to use Op-Amp in designing a circuit in making conventional Fire Alarm Circuit Sir? I know that using op amp is the cheapest to be used in making the circuit but i am encountering difficulties in designing th Circuit Sir thanks a lot Sir…
Hi Allan, it’s actually easy if you understand the basic working of an op amp comparator…you can refer to the following posts for more info:
https://www.homemade-circuits.com/comparators-using-ic-741-ic-311-ic-339/
https://www.homemade-circuits.com/how-to-use-ic-741-as-comparator/
https://www.homemade-circuits.com/how-to-build-simple-electronic/
Hello,
I must thanks your support which helped charging and discharging 12 V lead acid batteries with different capacity in parallel.
I plan to add current meter, logic switch and Arduino control in the future.
For the N-Channel Ideal Diode (second circuit) I plan to use:
IRFB7437PBF (0,8027 €) -N Channel-
– VDSS: 40V
– RDS(on): typ.1.5mΩ / max.2.0mΩ
– ID (Silicon Limited)250Ac
– ID (Package Limited)195A
For 12 V and 24 V solar panels:
1) Is the circuit the same?
2) Are Zener, Diode and Resistor values the same?
3) Should power values be chosen (Zener, Diode and Resistor) for so high N-Mosfet power?
Best,
Nacho
You are welcome Nacho!
Yes the MOSfeT is perfect, no problems.
The circuit will be the same for 12V and 24V. The zener and the resistor can be of any minimum wattage. The value of the zener and the resistor will be the same.
For the first circuit where will I put the led bulb to set the battery level.
2. How can I add a float charging feature to it instead of switching on and off.
Thanks
Don’t use the first circuit, use the second last circuit. Replace the op amp output zener with an LED to see the charging status.
Add a 100K resistor across pin3 to pin6 to latch it OFF once the battery is fully charged.
Keep a 1K 1 watt resistor connected across emitter/collector of the lower NPN. This will serve as the float charge voltage supply for the battery.
Remember, while setting up the preset you must keep the 100K latching resistor disconnected, reconnect it once setting up is complete.
Thanks Swag, I got lm358 how can I adapt it for it, having known the inverting, non inverting and the output.
Tolu, replace 741 with one of the op amps.
With the lm358 the output led doesn’t shut off just light on despite varying the preset
Did you check the comparator separately, by connecting it to a normal DC power supply?
see at the end of this video, how LM358 responds to preset turning:
https://www.youtube.com/watch?v=phPVpocgpaI
As the input voltage from solar is 18.5v, getting to the battery, is it safe for the battery, Sir
It is safe since the 18V won’t be constant and will keep getting lower with time…and also if the current is not a lot higher than 1/10th of the battery Ah (lead acid)
I am staying in the tropics with average of 6hours intense sunny day, all things equal, hope this is still safe because 3years ago I connected my panel differently to wet battery, within a month, the battery wet bad.
I that case you can use an LM338 based voltage/current regulator.
https://www.homemade-circuits.com/how-to-build-solar-panel-voltage/
Ok sir, I have tried lm317 regulator, is 338 efficient like zero ldo
LM338 is the higher current variant of IC LM317…LM338 is not an LDO, it will control the solar voltage accurately to the battery level. An LDO will pass the entire solar voltage to the battery…what is your requirement??
I need a output voltage of 14.4v to battery at high efficiency of 95% solar conversion. I have tried Lm317 solar regulator which had low efficiency
We have already discussed this, you will need a PWM buck converter which I referred to you earlier…
Please how can I prevent backflow from battery to solar panels at night, using diode reduces the efficiency. How can it be done that the diode line is activated at night to preserve the efficiency during the day
The two circuits on top are exactly for this purpose!
I raised the question because that is the issue I having at night with the circuit. Moreso, the diode in4148 is not in line of the supply, and the source and drain have supply from solar during day and battery at night
The MOSFET source is connected with the panel negative, which means during night the supply from the battery will have no effect no the MOSFET conduction. The MOSFET will respond and conduct only to the solar panel voltage, not the battery. The 1N4148 is only for safeguarding the MOSFET gate from reverse polarity.
When the circuit latches at full charged, how will it reactivate charging.
which circuit are you referring to?
“Add a 100K resistor across pin3 to pin6 to latch it OFF once the battery is fully charged.” From your comment up, for the second to last circuit.
If latched how will it reactivate.
It will restore when the 100K is no longer able to support the latching, when the battery voltage drops to a lower level.
refer to the last diagram from this article for more details:
https://www.homemade-circuits.com/opamp-hysteresis-explained/
Sir,
Wish you a healthy and prosperous 2019.
Thank you BB, wish you all the same!!
Hello Sir, I am thinking about harnessing the excess radioactive frequency in space to be converted into electrical energy but it is too difficult for me to think of a circuit to be used. Can you enlighten me, Sir, if it is possible? I know it is quite a difficult Sir but if it is possible Sir can you help me also Sir in making the circuit Sir THANK YOU SO MUCH…
Hello Allan, did you mean radio waves? I tried to search about radioactive wave but could not find any relevant information, however radio wave certainly is abundantly thrown into the space by the many stars and supernovas and may need a lot of research and investigation to learn about its effective harnessing procedures
Sorry Sir, yes sir its radio frequency, i mean those excess radio frequency signal from transmitting antennas sir,..is it possible to harness that sir? thank you sir, i appreciate your immediate response sir..
Allan, I don’t think that’s possible, because Rf from space could be too weak near the surface of the earth, and may be scattered over a wide area, therefore getting a concentrated amount of RF which could do some useful work looks remote to me.
thank you so much Sir, I also have a problem of my Motorcycle’s CDI sir, can also ask your help Sir to come up with a circuit to test the condition of my motorcycles CDI Sir thanks…
Hi Allan, you can try the following concept
https://www.homemade-circuits.com/cdi-tester-circuit/
thank you so much sir..
you are welcome 🙂
Hi Mr swargatman.,
I have 50watt solar pannel and 12v/18amp pb- battery.im planing to set up these in a place where sun is shining good 6hours.what changes shuold i do in your circuits.
Hi Rasanga, you can use any of the last two designs for your applications….make sure your panel produces over 15V at 2 amps rate
HiSwagatam, Cold I use P-channel mosfet to avoid reverse currant in small panels? I have a very simple circuit with 3v/3w solar panel, a 3.2v lifepo4 3A battery and a stepup 0.9v controller usb. But I'm unable after 7h of full sun to charge the battery more then 30%. Do you have any advice apart how stop reverse current? Thanks in advance for your help. Andrea
Hi Andrea, yes you can configure a P channel BJT or mosfet with the positive of the panel and prevent reverse discharging of the battery….
alternatively you can also try a schotky diode for the same
Hi Sir, Thank-you so much for replying,
I made circuit but output 540 burn out after increasing input voltage. but there was wrong wiring connection.
I used Ic lm358 as it is, can I use irf p250n instead of irf 540? I have also connected Ic2 of pin no8 to supply line directly, is it OK? because when input voltage will increase to 100 volt so it may get damaged ics.
There is no voltage on second opamp pin number 7, after turning present of Ic2, and IC1on pin no 5 I am getting 3.5 to 4.5 voltage, currently using 12 and 24 volt DC supply to test circuit, please suggest me what to do?
Mahesh, I wil reply it here, but for further discussion please post under the same article which we are discussing:
https://www.homemade-circuits.com/2013/04/solar-water-heater-with-battery-charger.html
do not bother about the right side opamp, first make sure the left side opamp operates correctly.
for this apply around 18V input from the solar panel side…then adjust RV1 such that the voltage at the cathode side of D1 becomes 14V…you can connect an LED in series with the base of T1 to ensure that T1 is shunting the excess voltage to ground.
first do this and make sure no matter how much the input is increased , the cathode side of D1 stays at 14V fixed.
this might make T1 very hot…use a large heatsink while doing this.
I will talk about the other parameters once you finish this….
Hi Sir, Mahesh Lalya here last four days back we talk to you regarding DC voltage control digram for wind wheel generator my generator generates 30 volt @ 4.5 amp normal speed and max may be 100 volt you send me circuit diagram using of solar-water-heater-reg circuit not able to read value of some resistors as flows r7/r6/r9/r10/r11 also can I use opamp as 741 with replacements of LM358 and can I use t1 as IRF9540, & T2 as tip147 and T3 as 840. & D1 as blocking diode,. Or email me on maheshlalya@gmail
Com Z's not able to find that link also because website had changed now. Pls replay soon
Hi Mahesh, yes the previous comments are lost due to a change in the site platform, I am sorry about that.
please click on the diagram to get an enlarged view of it and you will be able to see the parts clearly.
the IRF9540 is a P-channel mosfet and TIP147 is a PNP device and both of these will not work….because it needs to be N mosfet and NPN BJT as per the circuit's requirement….so please change them to IRF540 and TIP142
2nos of IC 741 can be used instead of LM358
hello sir can i adapt your circuit for experimentation sir? i was amazed because it is more efficient as compared to other commercial designs, you're so great sir, instead of an op amp sir what other component can i replace to it?
Thank you Allan, surely you can use the design for your requirement, however can you please elaborate why you think it's more efficient, because you are yet to test it practically ?? 🙂
just a curiosity, that's all
sorry you cannot replace the opamp by anything else since it's the most efficient and straightforward device than anything other option
hello sir,can i adapt your circuit sir for experimentation sir? thanks …
why your circuit need to use op amp and zener diode? may I use 3v3 Zener diode?
for enabling a reference voltage for the opamp, the value is not critical
Hi Sir How do I prove there is not voltage drop ?
the max output voltage will show equal to the input voltage from the solar panel
1) Hi Sir may I use TIP31C transistor?
2) I follow (NPN BJT) construct the circuit only the voltage regulator work only I have no idea.
3) There are extra ground connect below BC547?
4)if the solar panel out greater than 14.4v it will turn off the transistor?
Hi Swagatam, I want to know your opinion with regards to our solar system. Each panel rated 310W, total of 32 Solar Panels and divided into two groups (16 each) and connected to Growatt 4000. I was wondering, the Power output from the solar produces only around 2289W from the LCD Display. if we total all 32 panels with 310W rating that is around 10KW. How come it did not even reach a 3KW output from the growatt display panel? PV voltage output is 275Vdc (both PV1 & PV2)… Please advise…
Hi Dwines, It would be difficult for me to judge why the display is not showing the assumed wattage, however the best way to confirm this is by practically checking the voltage and current of each of the panels at a given instant and then comparing it with the display reading, if the display reading shows some other vague reading then it can be considered as incorrect and misleading.
or alternatively you can simply measure the V and I at the junction of the parallel connection and check the actual final wattage delivered at this combined junction for confirming the same…
hi sir,
can i use two or three irf 540 to charge higer voltage and current battries.such as 120 v and 40 amp charging current.thanks
Hi Ravipal, I don't think IRF540 is rated at 120V…you may have to go for some other fet rated above this limit…