This circuit is capable of providing as high as 25 Amps of current at any specified voltage between 1.25 V to 30V as per the adjustment of the given pot. The current is constant irrespective of the voltage settings. The circuit can be used for charging batteries in range of 50 to 200 AH.
How it Works
The figure below shows a straightforward design of a simple high current solar battery charger power supply circuit which would generate a constant 25 amps of current from any source which is able to generate currents in excess of 25 amps and at 32 volts maximum.
We know that the IC LM338 is specified with a maximum of 5 amp current, the IC restricts anything above this limit.
By connecting 5 of these ICs in parallel it thus becomes possible to generate a current output of about 25 amps. The great thing about using these ICs is that, these devices are internally protected from thermal runaway situations and short circuit or overload conditions.
It means the present circuit automatically becomes safe from such adverse parameters and thus becomes completely indestructible given the input is not exceeded above 32 volts.
However the ICs cannot be directly connected in parallel, because that would cause a difference in the voltages at the output from each of the ICs which in turn would cause an imbalance between the IC dissipation, this wouldn't be good for the overall functioning of the circuit.
Therefore the additional components in the form of the opamp and the transistor have been included in the circuit which controls and maintains a constant voltage output from all the ICs keeping the situation well under control.
What is the wattage of the 0.1 ohm resistors?
0.2 x 5 = 1 watt
Hi Swagatham,
this circuit is what i need for a long time, but unfortunately my panels are 36 volts so is it possible to make this circuit for 36volts input?
Hi Cem, 36 V is the maximum working limit for LM338 so I won’t recommend driving the IC at its maximum limits. By the way it is possible to create a good charger using a single MOSFET arrangement.
Please specify your solar panel V and I details and also the battery’s V and Ah details I will try to suggest a suitable design.
You are really a great man Swagatam, thank you very much. I have five sun panels 320watt per, Voc=39v max and Isc=10A. They are in parallel design and 50Amps to drive 24v water heater or some other heating tools for handcrafts such as small oven, plastic melting toll, soldering irons etc. I have bought an 50A mppt controller already but it couldn’t manage and now it is out of order. My aim is to get maximum amps at 24v to heat my needs quickly and also security for the panels. By the way my gel battery pack is 24v at 300AH
No problem Cem, I think a buck converter will be more efficient for your application than a complex MPPT. You can include the following concept with each of your panels and then combine the individual buck outputs to get the intended high power optimized output.
PWM Solar Battery Charger Circuit
THe output can be change to be 24 V by adjusting R8/R9 values appropriately
Alternatively you can also try the following concept:
https://www.homemade-circuits.com/lm317-variable-switch-mode-power-supply/
However you may have to upgrade the Q1 transistor and the coil wire thickness for getting the 10 amp output
Here’s another design perfectly suitable for your application:
https://www.ti.com/lit/ds/symlink/lm5145.pdf?ts=1592229037795&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLM5145
Thanx again Swagatam, I will try your suggestions and after now I am a big fan of you. Best wishes.
You are most welcome Cem!
HELLO AGAIN LONG TIME FOLLOWER OF YOUR BLOG I HAVE BUILT MANY OF YOUR CIRCUITS THIS IS MY PROBLEM I HAVE A 12V LITE THAT I LIKE VERY MUCH BUT IT HAS AN INCANDESCENT BULB AND AS YOU KNOW THOSE BULBS ARE A THING OF THE PAST. COULD YOU DESIGN A SOFT START CIRCUIT TO PROLONG THE LIFE OF THE TWO BULBS I HAVE . THANKS SO VERY MUCH
Thanks Bruce,
you can try the following circuit:
https://www.homemade-circuits.com/wp-content/uploads/2019/02/soft-start-for-bulb.png
Hi
I want to know it will be work on atransformer or a solar panel or both
it will work with all types DC inputs
pls send the 1a , 5a and 10a charger circuit for solar panels. i have tried with so many circuit but i am not getting exact output from that please send detailed circuit for solar charger with charging, battery low and battery full indications
you can try the following circuit:
https://homemade-circuits.com/2012/04/how-to-make-solar-battery-charger.html
use LM317 for amp…LM338 for 5 amp and LM396 for 10amp.
use a 18v panel and a 12V battery with the panel…
Hello Sir,
Sometimes the electricity can be unstable at times. But will need stable voltage to charge batteries so is it possible to have constant voltage and at the same time have a desirable constant current range depending on how many batteries I want to charge.
Basically if i have 3 (12v)batteries and I want to charge just one of them, I want to be able to selext the charging current and voltage. Then if I want to charge two batteries connected in series to give 24v then I want to selxt charge current and voltage too.
Kind of like a flexible charger.
I don't mind how many IC I have to buy but is IR doable.
Hello Michael,
yes it's possible, you can follow the instructions as given in the following articles in order to altyer the specs as per your specific needs:
https://homemade-circuits.com/2015/07/designing-customized-battery-charger.html
https://homemade-circuits.com/2015/07/designing-customized-battery-charger_13.html
Hi Swagatam,
Thanks. Can i use 2-3panels in parallel with this circuit to get 16-24 amp. Or can i add the fourth one too for getting close to 32 amp peak and generally around 20-28 during most day.
Regards
Gopal
Hi Gopal, yes that surely is possible, you may go ahead with it.
What is the power rating of resistors?
0.1ohm @ 5Watts?
the rest of the resistors @ 0.5 Watts?
yes, will do.
Hi Swagatham,
I want to use the above circuit, however the Solar panels have rated voltage as 30.04 and are generally recording about 31-32.5 Volts/8 Amp when placed in Sun, will I be able to use this circuit for charging 150AH batteries.
Gopal
Hi Gopal,
The above circuit will be able to handle upto 25amps, so according to me you can use it for charging a 150AH battery easily with the mentioned solar panel, but 8amps won't be sufficient and make the process very slow