In this post I have explained how to construct a simple solar panel regulator controller circuit at home for charging small batteries such as 12V 7AH battery using small solar panel
Using a Solar Panel
We all know pretty well about solar panels and their functions. The basic functions of these amazing devices is to convert solar energy or sun light into electricity.
Basically a solar panel is made up with discrete sections of individual photo voltaic cells. Each of these cells are able to generate a tiny magnitude of electrical power, normally around 1.5 to 3 volts.
Many of these cells over the panel are wired in series so that the total effective voltage generated by the entire unit mounts up to an usable 12 volts or 24 volts outputs.
The current generated by the unit is directly proportional to the level of the sun light incident over the surface of the panel.
The power generated from a solar panel is normally used for charging a lead acid battery.
The lead acid battery when fully charged is used with an inverter for acquiring the required AC mains voltage for powering the house electrical. Ideally the sun rays should be incident over the surface of the panel for it to function optimally.
However since the sun is never still, the panel needs to track or follow the suns path constantly so that it generates electricity at an efficient rate.
If you are interested to build an automatic dual tracker solar panel system you may refer one of my earlier articles.
Without a solar tracker, the solar panel will be able to do the conversions only at around 30 % efficiency.
Coming back to our actual discussions about solar panels, this device may be considered the heart of the system as far converting solar energy into electricity is concerned, however the electricity generated requires a lot of dimensioning to be done before it can be used effectively in the preceding grid tie system.
Why do we Need a Solar Regulator
The voltage acquired from a solar panel is never stable and varies drastically according to the position of the sun and intensity of the sun rays and of course on the degree of incidence over the solar panel.
This voltage if fed to the battery for charging can cause harm and unnecessary heating of the battery and the associated electronics; therefore can be dangerous to the whole system.
In order to regulate the voltage from the solar panel normally a voltage regulator circuit is used in between the solar panel output and the battery input.
This circuit makes sure that the voltage from the solar panel never exceeds the safe value required by the battery for charging.
Normally to get optimum results from the solar panel, the minimum voltage output from the panel should be higher than the required battery charging voltage.
Meaning, even during adverse conditions when the sun rays are not sharp or optimum, the solar panel still should be able to generate a voltage more than say 12 volts which may be the battery voltage under charge.
Solar Voltage regulators available in the market can be too costly and not so reliable; however making one such regulator at home using ordinary electronic components can be not only fun but also very economical.
You may also want to read about this 100 Ah Voltage Regulator Circuit
Circuit Diagram
NOTE: PLEASE REMOVE R4, AS IT HAS NO REAL IMPORTANCE. YOU CAN REPLACE IT WITH A WIRE LINK.
Track side PCB Design (R4, Diode and S1 not included...R4 is actually not important and may be replaced with a jumper wire.
How it Works
Referring to the proposed solar panel voltage regulator circuit we see a design that utilizes very ordinary components and yet fulfills the needs just as required by our specs.
A single IC LM 338 becomes the heart of the entire configuration and becomes responsibly for implementing the desired voltage regulations single handedly.
The shown solar panel regulator circuit is framed as per the standard mode of the IC 338 configuration.
The input is given to the shown input points of the IC and the output for the battery received at the output of the IC.
The pot or the preset is used to accurately set the voltage level that may be considered as the safe value for the battery.
Current Controlled Charging
This solar regulator controller circuit also offers a current control feature, which makes sure that the battery always receives a fixed predetermined charging current rate and is never over driven. The module can be wired as directed in the diagram.
The relevant positions indicated can be simply wired even by a layman. Rest of the function is taken care of by the regulator circuit.
The switch S1 should be toggled to inverter mode once the battery gets fully charged (as indicated over the meter).
Calculating Charging Current for the Battery
The charging current may be selected by appropriately selecting the value of the resistors R3.
It can be done by solving the formula: 0.6/R3 = 1/10 battery AH The preset VR1 is adjusted for getting the required charging voltage from the regulator.
Solar Regulator with Adjustable Voltage and Current Output
The following figure shows a high current voltage regulator circuit using the LM338 ICs.
The high current is achieved by connecting many number of LM338 Ics in parallel over a single common heatsink.
The parallel LM338 are not shown in diagram but while building it practically you can connect at least 8 numbers of LM338 ICs in parallel.
The input voltage can be as high as 50 V if LM338 HV IC is used.
The BC547 transistor is used for current control by adjusting the resistance at its base using a resistor ladder.
When many LM338 ICs are linked in parallel, the load current may be shared, enabling the circuit to tolerate larger currents.
As per the rules it is vital to remember that the output voltage of each IC may not be precisely the same, resulting in uneven load current sharing.
To avoid this, connect a tiny resistor (such as 0.1 ohms) in series with each IC's output to equalize current sharing.
However, as we have already mentioned that the ICs must be connected over a single common heatsink so that the heat dissipation can be shared and the ICs conduct equally. Therefore, adding a 0.1 ohm resistor may not be critical.
The BC547 transistor connected to the ADJ pin of the LM338 acts as a current sink for the IC, allowing the current to be adjusted by changing the resistance at the base of the transistor.
The resistor ladder connected to the base of the transistor allows for easy selection of the desired current level.
Overall, this circuit provides a high current, adjustable voltage regulation solution using the LM338 ICs in parallel.
However, it's important to ensure that the heatsink can handle the heat dissipation of multiple ICs operating at high currents to prevent thermal issues.
Solar Regulator using IC LM324
For all solar panel systems, this single IC LM324 based guaranteed efficient regulator circuit offers an energy-saving answer to charging batteries of the lead-acid type typically seen in motor vehicles.
Not taking into consideration the price of the solar cells, believed to be in front of you for use in various other plans, the solar regulator on their own is below $10.
As opposed to a number of other shunt regulators that will redirect current through a resistor once the battery is completely charged, this circuit disconnects the charging supply from the battery eliminating the need of bulky shunt resistors.
How the Circuit Works
As soon as the battery voltage, is under 13.5 volts (usually the open-circuit voltage of a 12 V battery), transistors Q1, Q2, and Q3 switch on and charging current passes through the solar panels as intended.
The active green LED shows the battery is getting charged. As the battery terminal voltage nears the open-circuit voltage of the solar panel, op amp A1a switches OFF transistors Q1-Q3.
This situation is latched for so long as the battery voltage drops to 13.2 V, whereafter the triggering of the battery charging process is again restored.
In the absence of a solar panel, when the battery voltage keeps dropping from 13.2V to roughly 11.4 V, implying a totally discharged battery, A1b, output switches to 0V, triggering the attached RED LED to blink at a rate fixed by the astable multivibrator A1c.
In this situation blinking at a rate of 2 hertz. Op amp A1d gives a reference of 6 V to retain the switching thresholds at the 11.4 V and the 13.2 V levels.
The proposed LM324 regulator circuit is designed to cope with currents up to 3 amperes.
To work with more substantial currents, it may be essential to make the Q2, Q3 base currents higher, to ensure that all these transistors can maintain saturation throughout the charging sessions.
Solar Panel Regulator Circuit using IC 741
The majority of typical solar panels provide around 19V off load.
This enables to get a drop of 0.6V over a rectifier diode while charging a 12V lead-acid battery. The diode prohibits battery current from moving via the solar panel during night.
This set up can be great so long as the battery does not get overcharged, since a 12V battery can easily become overcharged to above 1V5, in case the charging supply is not controlled.
Voltage drop induced through a series pass BJT, typically is approximately 1.2V, which appears to be way too high for nearly all solar panels to operate effectively.
Both the above flaws are effectively removed in this simple solar regulator circuit. Here, energy from the solar panel is supplied to the battery via a relay and rectifier diode.
How the Circuit Works
When battery voltage extends to 13.8V, the relay contacts click, so that 2N3055 transistor begins trickle charging the battery to a optimum of 14.2V.
This full charge voltage level could be fixed a bit lower, despite the fact that most lead-acid batteries start gassing at 13.6V. This gassing is significantly increased at overcharge voltage.
The relay contacts operate the moment battery voltage drops under 13.8V. Battery power is not utilized to operate the circuit.
The fet serves like a constant current source.
Shunt Type Solar Voltage Regulator Circuit
The shunt type solar panel regulator circuit shown above can be understood with the following points:
The op amp TL071 is configured like a comparator.
The FET BF256 along with the 500k preset P1 forms a constant current and constant voltage reference generator for the inverting input of the op amp.
THe pin3 which is the non-inverting input for the op amp is held with varying voltage source depending on the level of the battery terminal voltage, therefore this pin3 works like the over charge sensing input of the compartaor op amp.
The preset P1 at pin2 of the IC is adjusted in such a way that the potential at pin3 input of the IC is just higher the pin2 as soon as the battery reaches the full charge level.
While the battery level is below the full charge value, the potential at the pin3 is lower than the pin2 which keeps the output of the op amp to zero logic, and the FET T2 BUZ100 remains switched OFF.
However, as soon as the battery reaches the full charge level, the pin3 potential now increase above the pin2 value, which causes the output of the op amp to change state to a high output.
This immediately switches ON the FET T1, which shunts the solar panel voltage to ground, thereby preventing any further charging of the battery.
While the solar panel voltage is being shunted by the FET T1 via the diode D4, these two devices can get substantially hot, since the whole solar panel power gets grounded by these two devices.
The diode D3 ensures that once the battery is charged, it never gets discharged through the solar panel, especially during the night time.
The LED D1 indicates when the battery is fully charged and cut off, as it gets switched ON.
Parts List
Hi if the voltage out of the solar panel inverter and onto the house dis board is the same voltage level as what the grid is supplying then is it accurate to say that there is no potential difference so if the house is using 10amps then this will be 5amps from solar and 5amps from the grid. Also if the solar panel voltage is the same as the grid how can the solar panel supply current into the grid as againbhhere is no potential difference to allow any current to flow.
Hi, I am actually not very sure, I think the grid AC being more powerful than the solar inverter, it will alone supply all the power to the load, and no power will be extracted from solar inverter. The inverter power will be consumed only once the grid voltage begins to drop.
I have a 5.4 kw solar array on my house generating 240v activated by PGandE voltage. No battery system. It is tied to my house panel. If PGandE goes down. I lose power. No sychronizing voltage. I also have a gas 6kw generator that I can connect to my house panel through a transfer switch. It could provide sychronizing voltage that would activate my panels. However, I have been told that would destroy all electrical devices in my house. I don’t want to buy a Tesla power wall to regulate the voltage. Any suggestions.
I did not understand what you meant by: “It could provide synchronizing voltage that would activate my panels…”
Do you mean the generator voltage would replace the panel voltage?
If this is done with proper isolation through a changeover relays, then I do not see why your electrical devices could get damaged?
Ok sir , I will match the coil ( removed and taken from other cooker circuit 2000watts ) and capacitor is resonance at 25Khz. I will measure its frequency before removing it. Then using yours IR2153 circuir I will connect it to a 300 watts 36V ( 100w-12V X 3 nos series) solar panel directly . There will be no other circuit or user interface or display. Let us see. I have decided to go ahead with this test. I will give you the result. It will take some time. I hope very much that it should work else I will make my coil and operate it at resonance.
J K barik
No problem jk, hope it works for you, wish you all the best!
But I will use separate circuit ( yours IR 2153) but same coil and capacitor of 2000watts cooker.
Same frequency. Current is reduced so I should get low power.Why not?
That is not possible, every circuit has its own matching coil/capacitor….you cannot use a different capacitor set up with some other circuit.
If you want to reduce wattage, just reduce the input current, without changing the voltage. So if you want to reduce 2000 watts/300V circuit to 200 watts, then you can probably use a 300 V, 0.7 amp solar panel.
Inside a 2000watts induction cooker the coil works with 300V dc and 25Khz. If I give 30V dc from solar panel then will it give 200 watts ?
I don’t think so it will work with 30V, because there’s a huge difference between 300V and 30 V, and the circuit is designed to work with high voltage so a 30% to 40% reduction can be managed but not this much. But there’s no harm in trying it
I would rather not go with a Mppt.
I am putting 3x 50w 12v (17.6 vmp) solar panels in series on my ebike solar trailer to charge my 36v Li-on 12Ah battery. Can you show me a simple circuit that would prevent the battery from over charging.
I also have a second bike with a 48 volt 14Ah battery and I will be putting 4x 50w (17.6 vmp) solar panels in series on that one.
The last circuit is the one which suits your requirement perfectly. You can try that….for 3 panels you may have to use 3 MOSFETs (T2) in parallel, and same must be done with the D3 D4….just make sure to clamp the parallel devices over a common heatsink, individually for all the 3 devices.
However the IC can withstand at the most 36 v…so you may want to add a 35 V zener diode across the pin7 and pin4 of the IC…and also add a 1K 2 watt resistor in series with D2
Hi!
Fell over your site, hunting cheap and DIY made solar panel regulators.
I have a panel 15 W 18-20 Volt and I will charge a battery 12 Volt 14Ah AGM. Just curious, if I can only use the voltage regulation with LM338, without the current regulation. My calculation for my batter would be charging current of 1.4 A and that should be a resistance of 0.43 ohms, Correct?
If I don’t use the current regulation, then the solar panels max current (most bright sun and angel), should go to the battery? I don’t think the solar panel can exceed 1.4A Correct?
So for AGM 12 Volt and +22°C I should set the voltage regulator for 14.4 – 14.6 Volt. Correct?
Regards
Ham operator SM6GZL
Hi,
your assumptions are correct, since the solar panel cannot produce more than 1.4 amps, your battery is safe from over current, under all circumstances.
The result 0.43 ohms as calculated by you is also correct in case you use the specified current limiting feature.
Just make sure to adjust the LM338 output voltage to 14V which will ensure that your battery remains safe even without an over charge cut-off facility
Ok, Thanks! You say 14 Volts as maximum voltage for the battery. I think you mean when fully charged?
This Swedish site from a big producer of batteries in Sweden, let you to drag the thermometer and it will calculate the max charge voltage, with given temperature. It’s in Swedish, but it’s quite easy to understand.
Here is a Google translate of the page:
“OPTIMAL CHARGING VOLTAGE
Did you know that the temperature in the battery and the environment play a role in the battery’s charging capacity?
Most of all lead batteries and chargers are designed according to standards where the temperature is approx. + 25 ° C. This means that if you charge the battery at + 25 ° C, an optimal charging voltage for a standard battery is about 14.8 volts, and for an AGM or gel battery about 14.4 volts.
As the temperature drops, the resistance inside the battery increases. In order to achieve a proper charge, the voltage must therefore be increased. The opposite effect is obtained if the temperature is higher than approx. + 25 ° C. Then the charging voltage must be lowered, so that the battery does not get an overcharging which causes wear in the battery and higher water consumption.
We still do not recommend charging the battery with much more than about 15.5 volts, because you want to protect the electrical system in the vehicle. The battery chargers from Exide have automatic temperature compensation that provides optimal charging at all temperatures and for all battery technologies.”
Any thoughts about this?
Yes that’s right you must adjust the optimal full charge voltage to the battery as per the ambient temperature conditions in that area.
Hi Swagatham,
May I know the role to transistor in this ckt how it control current.
Hi Haron, it is for keeping the output current constant, or restricted below a threshold determined by the resistor R3.
Is it work as a series pass element.
No it is not a series pass, it grounds the ADJ pin of the IC to shut down the IC output whenever a high current is detected
Thank you for clearing my doubt in due course of time
regards,
Haron V Thomas
I have an old VW bug equipped with the typical generator with a voltage regulator which is located next to the battery under the back seat. I do alot of camping and I have solar panels to keep my bugs battery charged. Last night the voltage controller for my solar panels failed. So I was thinking what if I used the voltage regulator in my bugs charging system as the voltage controller for my panels?
The whole idea was for my panels to charge my bugs battery so I wouldnt have to keep starting the bug to recharge its battery. Wouldnt the solar panels act as the generator if connected to the voltage regulator. I know that the generator puts out AC, and the voltage regulator rectifies it to DC. But the solar panels are DC, with more voltage and less current.
Yes you can add the existing regulator circuit for controlling the panel output…
Hi
Bit of a long shot, but here goes,
I am trying to design a system that can recreate ‘natural’ light to a dark area of my house.
Installing a light tunnel is not practical.
My plan was to install a solar panel that can drive an led lamp, so when the sun is up the lamp works and at night it’s off, to keep a natural light cycle !
As I don’t want it to work at night, do I need a battery in the circuit ?
Thanks for any input
Regards
Kiaora
Hi, a battery will simply not be required, because once it gets dark the lamp will naturally shut off due to lack of power. You can use a DC LED bulbs which will perfectly replicate the sun illumination levels, and will slowly fade out as the sun goes down, until finally it shuts off.
i have a common charge controller(cheap type) have been using for my solar panels for 5years which is 98%+ efficient. i learnt voltage regulator is 30-60% efficient and best efficient regulator is no regulator which could be harmful as you said in “why we need a regulator” above.
please, which topology could be used in the charge controller to have such efficiency
You can connect the panel directly with the battery if the voltage difference is only 3 or 4 volts and current is within safe limits.
Voltage regulator will only drop the voltage, they won’t convert excess voltage to current, in this respect they can be inefficient.
If you want to convert excess voltage to equivalent amount current for the battery then you will need a buck converter.
Sir here why used transistor
to limit maximum charging current to a safe value
Sir I have two solar pannels of 150 Watt in parallel. now I need to make this circuit so please send me complet circuit through my mail.
Thanks Swagatam Majumdar
ijazwazir94@gmail.com
Ijaz, please specify the voltage of the panel, and the voltage/AH of the battery, so that I can suggest you the right data
First sorry, my english is bad.
I know, this is old thread, but i have one question.
I have one this : napelemvasarlas.hu/termekek/napelem/adatlapok/Trina_Solar_PC5.pdf
and one 45 ah battery.
Will this to work ?
R3=0.5 ohm / 5W standard resistor is good ?
Or i need to build buck converter to input ?
This will be good with IRF 540 ? :
https://www.homemade-circuits.com/2013/06/universal-ic-555-buck-boost-circuit.html
yes it will work, but make sure the panel voltage is above 15V, and current above 5 amps.
buck converter won't be required unless you want something too efficient…
I am building a model of a solar panel house for middle school students. One of the circuits I’d like to show is solar panels connected directly to a simple 12vdc -115vac inverter without a battery (no sun, no power).
Since the output of the panels varies from about 10 -18volts, I’d like to regulate it at about 12-13vdc. Can I use your solar panel voltage regulator circuit which uses an LM338 regulator without a battery to connect directly to the inverter (switch S2 connected directly from LM338 to inverter)?
yes definitely you can use it, if possible replace the IC with a LM196 or LM396 so that the max current handling capacity can extend upto 10 amps max…
Hi magheis, yes it can be done if the solar panel is adequately rated to handle the inverter load.
HiSir: can an inverter be powered directly from solar panel
hi. great circuit you got there. can i ask if the circuit can withstand 48V from the solar panel? and if not can i use a voltage divider in the input of the voltage regulator to lowered the input voltage?
I'm glad you liked it…
no 48V cannot be used at the input neither a resistive divider would work…..you can try the following design instead for your specific requirement
https://www.homemade-circuits.com/2012/01/how-to-make-versatile-variable-voltage.html
I have powerbank capacity of 30Ah and what the value R3 if I want 5V and 1A in order to charge my powerbank
It will be 0.6 ohms, 1/2 watt
Beni, the formula is given in the datasheet of the IC, please confirm it for assurance.
By the way what results are you getting?
Sir!i see this subject was before 3 years a go,i m a new one.anyway still not too late to learn.pls help me.
i saw a formula to solve the same equation,but diffrent result.Vout=1.25(1+R2/R1).is it something another.
thanks.
counting on your help
hi sir may i ask do you have any substitute regulators for LM338 that i can use? i cannot find any LM338 here in my current location. my solar panel is a 50w 20Voc with 40AH battery. what are the values of R3 and R4? also why did you use a potentiometer? what's the purpose of the potentiometer? can i just use a fix resistor with 2k ohm value? thanks and more powers
Hi mamon, there's no replacement for LM338….may be you can try the following design instead:
https://www.homemade-circuits.com/2015/03/100-amp-variable-voltage-power-supply.html
Pot is for adjusting the output voltage, you can use a fixed resistor in place of the pot by calculating it suitably
hi swagatam,
i have 5 hp solor pump set running ,now i want to use for home when not in use for pumping water ,the panels connected in serious for vfd dc 700 volt ,now i want to convert dc 700 volt to ac so i can stepdown to 36 volt by transformer and feed this to battery for charging and using it for day time ,please give me any circuit
hi shiva, converting the 700V may not be required, we can get a lower voltage option through one of the solar panels or through a couple of them…what is the rating of each panel that you you have used in the array??
sir , we're going to get the inverter out of the circuit, will it have an effect in the circuit?
sir do you have complete documentation of this project??
whatever is given in the above article, that's all I could provide…
sir, where did you derive that formula?? "0.6/x=AH/10" ?? where did it came from??
from ohms law, and from the fact the a lead battery requires 1/10 of its AH rate for safe charging.
R3 = 0.6 x 10/battery AH…… for lead acid batteries
can we also have your articles about LED drivers sir,, ?
hessika, I have already published many articles on LED drivers, just type and search "led driver" you'll find them all….
can we get the inverter out of the circuit??
yes, it has nothing to do with the LM338 circuit.
sir i just want to ask about the formula in finding the value of R3, what is the basis of its derivation?
sure hessika, you can use the circuit as a LED driver also, I already have a few articles whee the same configuration has been implemented as LED drivers
thank you sir. and sorry, for i didn't know that my reply has been sent already. another question sir, can we use the circuit in other application instead of using it as battery charger?? like can we connect some LED lights as it's output??? thank you sir,. 🙂
I have explained the formula in the above comment.
you can use LM317 instead of LM338
i have 6V/2W solar panel, will this provide an output of 1.5-4.5 volts? i will use an eveready rechargeable battery 1.5V 1300mAh for the output battery
yes it will, you can use the above mentioned circuit for the application
do we need to use a heatsink for the voltage regulator?
yes it is recommended.
sir, good day! we have 6V/1W solarpanel, what value of R3 do we need to use if we have 2500mah or 1500 mah battery? Thanks sir.
sir, good day! we have 6V/1W solar panel, what value of R3 do we need to use if we have 2500mah or 1500mah battery? thanks sir.
hessika, for Li-thium ion use the formula
R3 = 0.6/AH
for lead acid
R3 = 0.6 x 10/AH
Hey,
I tried this one, but I failed with it. I have 2 solar panels (each 4,5V) LM338, BC547, 10k pot and other stuff (resistors, diodes). I connected it, but it doesn't work as it should. If I change the position of the solar panels, the voltage changes. It should not alter or am I missing something somewhere. Isn't LM338 here to adjust the voltage so it is not changing?
Thanks
the IC is not designed to boost an input voltage, it will only produce a max output that may be 1V lower than the input and a minimum that may be equal to 1.25V.
In your case the achievable output range would be from 1.25V to 3.7V
I connected solar panels in series, so I get between 8V and 9V. In the end I set it to be 5V (just like the USB port), but when the light is changing, the output voltage is changing. Isn't that bad for the battery?
And thanks for your fast reply 🙂
LM338 ICs have excellent line regulation feature, meaning the output will never deviate more than +/-1% regardless of input voltage changes.
I think there may be something wrong with your circuit connections or the IC could be faulty (duplicate)
You are right. I'll check my circuit again. I hope IC is not faulty.
Thanks and I'll replay again to let you know how I did.
Hello,
can you please tell me what modifications to be made on your schematics in order to obtain a 12V output to drive directly a 12V dc motor of max. 90W?
Thanks in advance for you answer.
Hi, for 90 watts you will have to use LM196 instead of LM338, rest everything will remain as is except R4 that can be removed since it does not play an important role in the design.
P1 should be a 10k pot, and R3 is calculated as follows:
R3 = 0.6/7 = 0.085 ohms or any nearby value will do,
P1 must be set to obtain 12V at the output….
the input must be above 13V but less than 30V
the IC will need an heatsink.
Hi Swagatam,
I have solar panels 240W, 30.04V,7.4A, (generating 31-32.5 V in sun with no load) Open circuit 36.5V, 8.4A. I want to build a Charge controller for Battery 150AH/180AH and want to connect this to Home inverter ( 12V single Battery/24V Double Battery) to be given to two schools I want to charge the battery from both the source solar (preferably during day time ) and Mains supply (during rainy reason/night).
Please let me know if I can use the above circuit such that inverter decides which power source should be selected and in absence of Solar power supply it should feed from AC.
Regards
Gopal
Hi Gopal, LM338 will not be able to charge a 150ah battery.
you can use two LM196 in parallel for the same, but a 30V panel with 7amp current won't be combatilble for a a LM196 or any such regulator
You will probably need a buck converter circuit, which would convert 30 x 7.4 parameter to 14 x 15 for the required charging
ok will lm337 work instead of 338? i cant find 338 here. and assuming a 50 watt panel what is the maximum wattage of an inverter it can operate safely? 1 have 1000 watts modified sine inverter. thanks again
337 is a negative regulator, you can use it but the configuration will need to be reversed entirely for getting the same results.
sir good day can you give me a simple schematic of a solar charge controller able to charge 200ah thru a 200 watts panel. parts here in the philippines are very hard to find so if possible use of common parts is very much appreciated. thanks and more power…
Aureliano,you cam try this simple zero drop circuit for your application:
https://www.homemade-circuits.com/2013/08/simple-zero-drop-solar-charger-circuit.html
with the schematics above what will be the value of r3 if my battery is 200aH? is it 120 or 120k? thanks
sorry, 200AH is far beyond the range of this circuit.
sir can you give me a simple schematic of a charge controller able to charge 200ah battery? my panels are 200 watts. parts in the philippines are very hard to find. thanks
dear Swagatam
i don't know much about electronic
does this circuit have a function to automatic turn off when battery is full?
Hello! Found this page very useful. Thank you for the detailed information. I am actually looking to build a solar charger to charge my NiMH rechargeable batteries which will in turn run a dc stepper motor. My NiMh batteries are 12V 2700mAh. The solar panels that I am using are TWO 6V panels with a power of 1.5W each. The DC motor’s working voltage is 12V and current is 0.33A. Will this circuit schematic work for the solar panel and the rechargeable batteries? How will I determine the resistor values? I will be very obliged if you can help me out. Also can I use a substitute transistor instead of the BC547 and use LM317T instead of LM338.
Thanks!
yes you can use the above shown circuit for your application. Since the charging current is within the range of the iC 317, it can be used in place of LM338.
The pot P1 should be adjusted for getting 14V at the output for the battery under charge.
The panel must be capable of generating in excess of 14V, may be a couple of voltages more.
R4 is not important so it may be removed.
R3 = 0.6/1 = 0.6 ohms 1/4 watt
BC547 can be substituted with any identical NPN transistor
You are welcome,
The circuit shown in the above artice includes a current control feature which can be dimensioned as per the requirement of the battery.
The circuit which you have shown does not have this feature.
For an automatic cutoff you can upgrade the previous circuit as per the last design provided in this article:
https://www.homemade-circuits.com/2012/07/making-simple-smart-automatic-battery.html
Thank you so much Sir. Also, in the circuit above (not the upgraded version but the one that is shown above on this page), you have not used a capacitor? Could be get by without one?
Also in the upgraded version (for which you provided the link in your above reply), I would need to use a NC switch? And the resistor values shown in the upgraded version are fixed or will they vary according to our battery specifications?
Really appreciate all the help and your prompt replies.
capacitor would be required only if the supply is derived from an ac source and the bridge is 6 inches away from the IC, it's not required for a DC source such as a solar panel.
sorry i did not understand what you meant by a NC switch?
R2 should be replaced with a 10k pot for adjusting the charging voltage as per the requirements.
and the BC547 emitter resistor must be selected as instructed in the above article.
I'm sorry to bombard you with a million questions but I had a few more queries (actually not so few). So for the circuit shown above on this page, are we using a toggle switch (one that is referred to S1 above)? and what is the inverter positive? So for my requirements where I am using two 6V solar panels (1.5 W each) to charge my 12V NiMh battery, the pot that I calculated was 2K. I just wanted to make sure that I was using the right one.
For the new circuit that you mentioned, R2 would be replaced with a 10K pot (instead of the 2K that I am currently using) but the resistors connected to the IC741 chip would have the values as shown in the schematic or would they differ according to requirements? And we're only using one pot in the new schematic, right? The rest are fixed resistors? Also would it be ok if I used the npn transistor 2N2222 instead of BC547? Lastly for this new schematic, the diodes connected to the positive of the battery need to be connected to a switch?
Sir, I am also somewhat confused about another facet. I am using my 12V NiMh batteries to run a DC stepper motor (driven by a H-bridge) and controlled by an arduino. the battery is used a backup power supply to run the motor whereas the primary supply would be AC (converted to DC through the AC to DC converter of the microcontroller). I was wondering firstly how would i connect my DC motor inorder to run it with the battery? Secondly can i incorporate some sort of option where the user can use either the direct power supply to run the motor or switch to running the motor from the NiMh battery pack?
I apologize for the plethora of questions. I am not extremely familiar with the circuitry and therefore am encountering these questions. I will be grateful if you can help me out with my queries. Thank you so much. =)
Inverter is the unit that converts battery voltage to 220V AC mains, here S1 is a switch which can be used to shift the battery from charging mode to inverter mode once it gets fully charged from the LM338 circuit, so that the inverter can be used for obtaining the intended 220V AC
A 10k pot will give a bigger adjustable range, so a 10k pot is better.
other parts associated with IC 741 will remain as given.
other than the 10k pot the 741 circuit includes a 10k preset which should be used for setting the over charge threshold.
2N2222 will be fine.
the battery (+) can be connected to the motor bridge via a 1N5402 diode and also stepped down to 5V via a 7805 IC for feeding separately to the arduino board, so basically that's 12V via diode to stepper bridge, and 5V via 7805 to arduino.
With so many initial doubts and questions, I fear there could be 90% chance that you wouldn't succeed with these circuits, especially the 741 automatic charging circuit, because it's for experienced hobbyists who are already well versed with the basics.
Dear Sir,
Thanks for patiently answering my questions. I know I'm a novice in this field but I guess I'll never learn until I experiment and make mistakes. Please excuse my ignorance though. So I had gone ahead and tried making the circuit above (I'm not trying to attempt the automatic cutoff circuit just yet) and well, the circuit 'seems' to be doing something but I'm not sure if it's functioning correctly. I just wanted to clarify whether I had my connections right. I did not include the switch and the inverter. For now I only want to recharge my battery using my solar panels and possibly control the charge current.
So I had the positive of my solar panel connected to one side of the diode. The other side goes to PIN3 (input) of LM317. I have one leg of the 220 ohms resistor coming out from pin2 of LM317 and the other leg attached to a 2K pot. I also have a connection from Pin 1 of LM317 with this end (wiper and leg1) of the pot. The other leg of the pot is grounded. Then from Pin 1 of LM317 I have attached pin3 of the 2N222 transistor. Leg 1 of the transistor is grounded and leg 2 is connected to one side of a 2.2ohms resistor. The other side of the resistor is grounded. Finally I have the positive of the battery connected to PIN 3 of LM317 and the negative is grounded. I am not sure if my configuration is correct. Is there a connection between R2 and R3? Are the negative of the solar panel, Emitter of the transistor, one leg of R3, one leg of the pot R2 and the negative of the battery all commonly grounded?
My desired charging current is 0.27A. I am using a 12V 2.7Ah NiMh battery and I am using 4 (4.5V) solar panels in series with a power rating of 1.5 W (each panel) and current rating of 0.334. When I connected an ammeter in series with the positive of the battery it gave me a 0.09A which doesnt seem alright. When I tested under a bright lamp right, the solar panel was giving a decent voltage output but the ammeter read 0.0A. When I took it outside, that was when it gave me 0.09A. I am not sure if my circuit is working correctly or I have connected everything correctly. Before connecting my battery to this circuit, I measured the voltage of the battery as 6.79 and after connecting it and putting it in the sun for a while, I disconnected and isolated the battery and tested the voltage which was then 11.04V. So is my circuit charging the battery? And why is the current so low? Should I not be getting something close to 0.27 A.
Again would appreciate it a lot if you can help me clear my confusions. Thank you 🙂
Dear Zara,
You will have refer to te datasheet of the IC 317 to correctly understand its pinout connections.
However, with the present connections if the pot rotation is giving a variable output then you can assume the connections to be right.
yes all the negatives sould be made into a common line as given in the diagram.
with an ammeter connected short the output of the circuit and check the current, if it's equal to the panels maximum amp value (1.5amp max for 317 IC) then you can be sure that the circuit and the panel are working coirrectly.
For 12V set the output to 14V, otherwise the battery will not initiate the charging process.
Dear Sir,
Thank you so much for being patient enough to answer my barrage of questions. I tried the above circuit without the inverter and it seems to be charging my 12V NiMh batteries. I had a few questions that I still had some doubts about.
Firstly, I have not tested running the DC motor on the battery as yet but I was wondering whether I will be able to use the above circuit to continuously charge my battery even while it is connected to the motor and running the motor?
Secondly, I was also confused as to how to determine Icharging or the current that is charging the battery. Does the ammeter connected in series with the battery positive and one leg of the R1 resistor measure Icharging? If that is not equal to the solar panel's max current but is below the charging current set by the transistor and R3, is the circuit working? Is the charging current provided to the battery different than the solar panel max current? And is the transistor basically also helping in trickle charging the battery? And would I be able to change Icharging? Or the current I am using to charge the battery?
Lastly, I am currently using 4 solar panels to get a dc input voltage but the system I am designing needs to be compact. Would there be a way I can use only a small solar panel with a low dc voltage and somehow step it up to charge the battery? I do not want the charging current t be affected though. Would I be able to use a transformer (or that would be only in the case of AC current) or a boost converter? If it is possible, could you please explain how I can integrate it in the above circuit? So if I have a panel outputting 4.5 volts and I want to step that up to 14V to charge my battery, would that be possible?
Sir, I would be very grateful if you could shine some light on my queries. I apologize for bombarding you with so many questions every time. Greatly appreciate your efforts. Thank you.
Dear Zara, here are the answers:
I have not tested running the DC motor on the battery as yet but I was wondering whether I will be able to use the above circuit to continuously charge my battery even while it is connected to the motor and running the motor?
No, including the motor will need the charging curent to be increased which might affect the battery when motor is switched OFF.
Secondly, I was also confused as to how to determine Icharging or the current that is charging the battery. Does the ammeter connected in series with the battery positive and one leg of the R1 resistor measure Icharging?
Yes, you can see the CHRG current in that way.
If that is not equal to the solar panel's max current but is below the charging current set by the transistor and R3, is the circuit working?
The current reading could be equal to the set value by R3 or less than that, but never above that no matter how large the input current may be..
Is the charging current provided to the battery different than the solar panel max current? And is the transistor basically also helping in trickle charging the battery? And would I be able to change Icharging? Or the current I am using to charge the battery?
R3 will not cause trickle charging. It can produce a lot more than that.
R3 can be changed only to change the charging current rate of the battery.
Lastly, I am currently using 4 solar panels to get a dc input voltage but the system I am designing needs to be compact. Would there be a way I can use only a small solar panel with a low dc voltage and somehow step it up to charge the battery? I do not want the charging current t be affected though. Would I be able to use a transformer (or that would be only in the case of AC current) or a boost converter? If it is possible, could you please explain how I can integrate it in the above circuit? So if I have a panel outputting 4.5 volts and I want to step that up to 14V to charge my battery, would that be possible?
Boost circuit can be used for increasing the solar panel voltage, only if the VxI of the panel is well above the VxI requirement of the output
i have 150 watt panel and its voltage is 15v to 20v, i want exact 12v for dc fans so is it the above circuit will work for me.
yes it will work but only with a capacity of 5 amps output
what is the value of R3 than?
and is it possible or any changes in the above circuit for 10amps output?
thanks for quick reply
R3 = 0.6/charging rate in Amps
R4 can be removed, it's not so important.
charging rate should be 1/10th of the battery AH
i dont use any battery want to use dc fan with it so how to calculate R3 than?
R3 = 0.6/5 amps = 0.12 ohms? is it correct if yes what will be the wattage
thanks alot
if your fans max current limit is 5 amps, then it's correct.
i have 40 watt panel with 2.3 a operating current but it charges only at 1 amp. 40ah battery.
what is the voltage of the panel and the battery?
2.2 amps will not charge a 70AH battery….you will need a 10amp panel for that.
No, this is just a basic regulator and not a complete charging station.
Pleased with the existence of your blog,
I am very confused with my project about solar cell phone charger.
In this case I use the former solar cell flashlights that produce voltages of 7-10 volts and want to reduce the voltage to 5 volts.
I have tried to use LM7805 but is only capable of producing the range of 3 V around to the scorching sun.
What types of ic regulator 5v with small amps??
Thank you
Thank you!
7805 is a very reliable IC and it will 100% produce 5V with a minimum of 7V input.
Check the compare input and output voltages using 7805 without any load connected, you will find exact 5V at the output of 7805.
No, not for overcharge, it's for controlling overload or short circuit at the output, it will not cut off the battery when it's fully charged.
It's for grounding the ADJ pin of the IC in case the the output load exceeds the preset current limit. This results in switching off of the IC and its output voltage to the load.
…..use it in place of 741
use one opamp from the four inside LM324, it will work for voltages upto 30V