How to charge a 4V lead-acid battery

Introduction- 

In this post, you will see how to charge a 4V lead acid battery. These batteries are commonly available to everyone. These lead acid batteries are the safest among the types of batteries available. They have about 33-42Wh/kg of specific energy and have 50 - 90% charge/discharge efficiency. 

Battery info- 

Nominal voltage = 4v

Rest voltage =~ 4.22v

Top voltage = 4.60-4.98v (Full saturation)

Float voltage = 4.5-4.6v (maintenance charging)

Charging the battery-

Method 1 - Charging the 4v LA battery by using 7805 IC. 

For more information on 7805 IC click here.

Circuit diagram- 

Use input supply of voltage greater than 7v

Materials required- 

1. 7805 IC 

2. Input power supply (V>7v)

3. Rectifier diode  ( Example - 1N4001)

4. connection wires and PCB.

Method 2 - By connecting 5v supply directly to the battery from Phone chargers.

In this method, you just need to cut a USB cable and then connect the Red wire to the battery positive and Black to the negative of the battery. 

And after connecting the wires plug in the usb connector to the usb port of your charger.