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Home » IC 555 Solar Charger Controller Circuit

IC 555 Solar Charger Controller Circuit

Last updated on 6 June 2026 by Admin-Lavi Leave a Comment

We can make small IC 555 Solar Charger Controller Circuit, as this circuit checks battery voltage from solar panel and when battery is full then the circuit stop power from panel.

Thus, this stop battery from overcharge and damage.

Circuit Working:

IC 555 Solar Charger Controller Circuit Diagram


Parts List:

ComponentsValuesQuantity
ResistorsR1 330Ω set to 14.9V 1/4 watt, R2 330Ω set to 11.9V 1/4 watt1
470Ω 1/4 watt2
Potentiometer 10k2
SemiconductorsIC1 5551
IC2 78051
Transistor BD1391
LEDs Red 5mm 20mA (charging indicator)1
White 5mm 20mA (general indicator)1
Green 5mm 20mA (dumping indicator)1
Switches Push button (for dumping)1
Push button (for charging)1
Diode 1N40041
12V relay (40 amp)1
Solar panel (16V 60W)1
12V battery1

To begin with, if our solar panel charge battery in less than 10 hours then only we need to dump extra current.

When battery is full then solar power goes to load and uses big resistor or 12V 100W bulb as load.

Also, if battery takes 14 hours or more to charge that is like two days sun, then battery charge slow with no damage which might not be in this circuit.

So, to charge without circuit connect high watt resistor and diode in line with solar panel and battery.

Furthermore, battery will charge slow over few days.

Also, use variable power supply instead of fixed panel and there is no need for high power resistor, battery, panel or relay.

Set power supply to 11.9V and then turn top 10k pot to light charging LED and set voltage to 14.9V.

Hence, turn bottom 10k pot to light dumping LED and before use connect all parts like circuit says and check voltage is right.

If IC1 555 does not work well under 5V so white LED lift 7805 IC2 output to 8.5V and then press any button quickly to start charge or dump.

IC1 555 change state to do charge or dump and if we do not have variable power source then put small 12V battery in circuit it will charge fast and we can see voltage change.

After that, watch how it goes between low 11.9V and high 14.9V and then adjust voltage set points each time it cycle.

Moreover, this test is easy but just wait battery to reach 11.9V and 14.9V and if possible use old junk battery for test.

How To Build:

To build a IC 555 Solar Charger Controller Circuit follow the below mentioned steps for connections:

  • First, put all parts same like in circuit diagram.
  • Then pin 1 of IC 555 goes to ground.
  • Next, pin 2 of IC 555 connect to push button 1 to ground and also connect R1 resistor from pin 2 to middle leg of P1 potentiometer.
  • After that, pin 3 of IC 555 connect to 12V battery (+) through red charging LED and resistor R3; also from pin 3 connect resistor R4 to base of transistor T1.
  • Now pin 4 of IC 555 connect to 12V battery (+) and also pin 8 of IC 555 also connect to 12V battery (+).
  • Pin 6 of IC 555 connect through resistor R2 to center leg of pot P2.
  • Then IC2 7805 input pin goes to 12V battery (+), IC2 ground pin goes to battery negative (–) and IC2 output pin goes to pin 4 and pin 8 of IC 555 and also give power to rest of 555 circuit.
  • After that, transistor T1 emitter goes to ground, collector goes to one side of relay coil and other side of relay coil goes to 12V battery (+)
  • Lastly, base of transistor T1 connect through green dumping LED and resistor R4 to pin 3 of IC 555.

Solar panel of 16V Connection:

  • Positive wire goes to relay common terminal and negative wire goes to ground.
  • Dump push button (button 1): pin 2 of IC 555 to ground and charge push button (button 2): pin 6 of IC 555 to output pin of IC2 7805.

Safety Tips:

  • Better to use ready made solar charge controller, as it has safety inside and is good for expensive battery and panel.

Conclusion:

Overall, this IC 555 Solar Charger Controller Circuit helps battery charge the proper way and it stops too much charge, protect battery and use power from solar panel slowly and safely.

Filed Under: 555 Timer Projects, Battery Charger Circuits, DIY Projects, Solar Circuits

About Admin-Lavi

Lavi is a B.Tech electronics engineer with a passion for designing new electronic circuits. Do you have questions regarding the circuit diagrams presented on this blog? Feel free to comment and solve your queries with quick replies

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