10 solar charger for 6V battery

This is a solar charger based on LM317 regulator IC. The charger is similar to the 6V charger project but made simpler. When battery has reached is full charge voltage (Bat voltage is higher than VDz + 0.7), the charger automatically cuts the charging to protect the battery form damage. The led light will indicate the full charge state in the battery. This charger will work only when the voltage from the solar panel is much higher than the battery voltage, unlike the solar charger with regulator and controller that can charge regardless the solar voltage.

charger schematic diagram

Part List:
Solar - 12V solar cells array
C1 - 470uF electrolytic capacitor rated 25V
D1, D2 - 1N5400 or any rectifier diode rated 2A minimum
Dz - 1N5235B or any 6.8V zener diode
R1 - 3 kilo ohms 1/4W
R2 - 330 ohms 1/4W
R3 - 560 ohms 1/4W
R4 - 2 kilo ohms 1/4W
LED -3mm or 5mm  Red or any low power LED
Q1 - 2N2222, CS9013, or similar NPN transistor
Bat - 6V lead acid battery

LM317 pins

2N2222, CS9013 pins

Note: You can convert the charger into 12V by replacing the solar panel with higher voltage ; zener diode DZ; and values of R2 and R1.

0 Solar Street Light circuit

Same with the normal street light, this one automatically turns on when environment is dark (night or gloomy rainy days) and off during bright day. An advantage of this lighting system is very easy to build since uses minimal and very common electronic parts. Another advantage is it uses solar power as main source of energy, thus no more 220V supply is needed and environment friendly. It has a built in battery that is charged during the day and supplies power during the night.

Street light circuit

Part List:
R1 - any light dependent  resistor (LDR)  2k to 1Meg
R2 - 50 kilo ohms 1/4W
R3 - 120 ohms 1/4w
R4 - 1 kilo ohms 1/4W
D1 - 1N5817, 1N5818 or any diode with low voltage drop
Dz - 2.7V zener diode rated 1W
Q1 - 2N2907, 9012, or similar PNP transistor
Q2 - 2N2222, 9013, or similar NPN transistor
Lamp - 1.5V to 2.5V rated flashlight bulb 30mA to 75mA
Bat - 2 NiCd cell rated 1.2V @ 800mAh or higher
Solar cells - MPT3.6-150 Flexible Solar  or any  3.6V @ minimum 100mA cells

If you plan to use LED instead of  lamp, just follow the diagram below. The resistance is equal to 10 ohms rated 1/4W. Use only red or orange LED to make it work. Other LED like white or blue requires higher forward voltage (see LED forward voltage table for more info ) and our source is around 2.4V only.

Replacing buld with LED

White , blue and other high intensity LED requires 3V to 3.6V forward voltage. Our battery can supply only 2.4V, thus impossible for us to use these LEDs using the same circuit above. But if you want to use these LEDs, try modifying the circuit above and add the joule thief circuit.

5 solar battery charger with charging controller and regulator

Solar power is a good and clean source of electricity.But  before it is used in houses, it is first used to charge battery then the battery, with the help of inverter circuits, will power up household appliances like lights and TV sets.

During hot sunny days, solar panels can generate voltage above 14V dc or higher , enough to charge a 12V lead-acid battery. But during cloudy days, solar panels can generate voltages even less than 9V to 8V, which is very low enough to charger a 12V battery. In short, during this days, solar panels are useless.
The purpose of this project is to design a low cost (cheap) and simple solar battery charger that has a built in charging controller and regulator that can maximize the solar panels charging capacity and at the same time help the battery charging process continuous regardless the weather is sunny or cloudy.

The project uses a 555 timer IC to generates pulses of voltages at a specified duty cycle and frequency. This generated voltage will be feed to the input of bipolar junction  transistor and as a result generates an output voltage which is enough to charge the battery. This operation is similar to 3V charger project. The circuit also has comparator IC  that  monitors charger output voltage  and  controls the charger off when the battery is fully charge. The comparator also controls the output to more than 13.6V (15V) to ensure proper and continuous battery charging. The project also has an output regulator that limits the output voltage  acceptable to battery charging.The charger project also has a voltage output indicator and a diode to avoid battery charge draining.