In this article, let us discuss the circuit for recharging the Lead Acid battery using the Solar panel. The concept of solar is not new for us. As day by day, non-renewable energy sources are reducing, and the usage of solar energy is improved. This energy is not only used on the Globe, but also used in space stations where no electrical power is accessible. Here is the simple circuit to charge a rechargeable Lead-acid battery (12V, 1.3Ah) from the solar panel. This solar charger has regulation of current, voltage and also has over-voltage cut off services. This circuit may also be used to charge the Lead-acid battery at constant voltage because o/p voltage is variable.
How To Recharge Lead Acid Battery Through Solar Panel
Solar battery charger worked on the principle that the charge control circuit will generate the constant voltage. The charging current permits to LM317 voltage regulator using the D1 diode. The o/p current and voltage are controlled by changing the adjust pin of the LM317 voltage regulator. The charging of the battery can be done by using the same current.
Specifications of the Charging Circuit
- Solar panel rating – 5W /17V
- Output Voltage –Variable (5V – 14V).
- Maximum output current – 0.29 Amps.
- Drop out voltage- 2- 2.75V.
- Voltage regulation: +/- 100mV
Circuit Diagram of Lead Acid Battery Through Solar Panel
The required components of the lead acid battery through solar panel includes Solar panel – 17V, LM317 voltage regulator, DC battery, Diode – 1n4007, Capacitor – 0.1uF, Schottky diode – 3A, 50V, Resistors – 220, 680 ohms, Pot – 2K and Connecting wires.
A solar battery charger circuit must have a changeable voltage regulator. So LM317 variable voltage regulator is selected. Here this voltage regulator can produce a voltage from 1.25-37V max & max current of 1.5 Amps.The adjustable voltage regulator has a typical voltage drop of 2 V to the 2.5V.So the Solar panel is closed, such that it has additional voltage than the load. Here the circuit uses a 17v/5w solar panel.
A 12v/1.3Ah Lead acid battery is used here and in order to charge the Lead acid battery, these are required. A Schottky diode is used to guard the voltage regulator and solar panel from reverse voltage produced by the battery when it is not charging.O/p Voltage & Charging Current
O/p Voltage & Charging Current
For charging the battery output voltage and charging the current include the following
Fix the o/p voltage to 14.5 volts
Current Charging = Solar panel wattage/Solar Panel Voltage = 5 / 17 = 0.29A.
Here voltage regulator can provide 1.5A current.So it is suggested to use high wattage boards if more current is necessary for your application. If the Lead acid battery requires primary current more than 1.5A, it is not suggested to use voltage regulator-LM317. Time taken to charging the battery is 1.3Ah/0.29A = 4.44hours.
Here, the solar panel has 5Watts. Power going into battery is 14.5*0.29 =4 watts Thus, 1 Watts of power going into the voltage regulator. All the above-stated parameters have to be taken into account before charging a Lead acid battery.
For 6 volts Application
Fix the o/p voltage to 7.5volts to 8 volts as mentioned on the battery.Calculate the power dissipation and charging current as shown above.
In this proposed system, power is limited due to the thermal resistance of the heatsink and voltage regulator. To maintain the temperature below 125 degree Celsius, the power must be incomplete to 10W. Voltage regulator(LM317) has an internal temperature limiting circuit so that if it becomes too hot, it shuts down routinely.
When the battery is charging, heat sink gets warm. When finishing the charging at max voltage, heat sink runs hot. This heat is because of excess power that not needed in the process of charging a battery.
As the solar panel offers constant current, it performs as a current controller. Therefore the circuit does not require any current limiting.
Protection of Solar Charger
In the above circuit, C1 capacitor guards from the static discharge. The d1 diode protects from the opposite polarity. And the voltage regulator offers current and voltage regulation.
Specifications of Solar Charger
- Solar panel rating: 12Vor 6V
- Volt range is 5V to14V
- The maximum power dissipation 10W
- Typical dropout value is 2 to 2.75V
- Max current is1.5A
- Voltage regulation is +/- 100mV
Operating the Circuit
- Give the connections to the circuit diagram accordingly.
- Arrange the solar panel in the sunshine.
- Now fix the o/p voltage by regulating pot RV1
- Check the Lead acid battery voltage with the help of a digital multimeter.
Advantages and Applications
- Output voltage can be adjusted
- The circuit is inexpensive and very simple.
- The circuit uses basic required electrical and electronic components.
- When no sunshine on the solar panel, zero battery discharge.
- This circuit is used to charge the batteries using solar energy.
- In this project, the current is limited to 1.5A.
- The circuit needs high drop-out voltage.
Thus, this is all about how to recharge a Lead Acid Battery through solar panel We hope that you have got a better understanding of this concept. Furthermore, any doubts regarding this concept or to implement any solar power charge controller project. Please, give your feedback by commenting in the comment section below. Here is a question for you, what are the applications of Lead Acid Battery?