4V Lead Acid Battery Charger

Note- You can use any Li-ion charger which is used to charge phone's 3.7v Battery as they both are charged with a 4.2V DC. but if you still want to make one of your own. just go through this instructable.

Here's a step-by-step guide to making a 4V lead acid battery charger using a 5V regulated supply:

1. Gather the materials needed for the project:

  - 5V voltage regulator (such as L7805)

  - Header pins or connectors for connecting the battery to the circuit

  - 1N4001 rectifier diode

  - ECB (Experimental Circuit Board), breadboard, or any other suitable prototyping board

2. Begin by connecting the components on the ECB or breadboard:

  - Insert the 5V voltage regulator (L7805) onto the board, ensuring it is oriented correctly.

  - Connect the input pin (Vin) of the voltage regulator to the positive terminal of your 5V regulated power supply.

  - Connect the ground pin (GND) of the voltage regulator to the negative terminal of the power supply.

  - Connect the output pin (Vout) of the voltage regulator to one end of the rectifier diode (1N4001).

  - Connect the other end of the rectifier diode to the positive terminal of the lead acid battery.

  - Finally, connect the negative terminal of the battery to the ground (GND) of the power supply.

3. Once all the connections are made, double-check them for accuracy and ensure there are no loose or shorted wires.

4. Plug in the 5V regulated power supply to a suitable power source.

5. The voltage regulator will regulate the input voltage to a steady 5V output, which will charge the lead acid battery connected to it. The rectifier diode prevents the battery from discharging back into the power supply.

Note: It's important to monitor the charging process and ensure the battery does not overcharge. Lead acid batteries typically require a specific charging profile to avoid damage or reduced lifespan. If you're unsure about the charging requirements for your specific battery, it's recommended to consult the manufacturer's guidelines or use a dedicated lead acid battery charger.

Remember to exercise caution when working with electricity and follow safety precautions to prevent any accidents.

To ensure proper functioning of the battery charger, it is essential to have a DC power source with a voltage greater than 7 volts. You have a couple of options to obtain such a power source. One option is to connect a laptop charger with a DC jack, while another option is to utilize a set-top box adapter. Once you have secured the appropriate power source, you can proceed with connecting the battery to the output of the voltage regulator.

For a more detailed visual representation of the circuit, please refer to the provided pictures.