## Wednesday, November 2, 2016

### Circuit Schematic Diagram LiPo Battery Charger using LM324 IC

ElcoHow. - This is one circuit schematic diagram of  LiPo Battery Charger using LM324 IC that very useful for you who want to build LiPo battery charger this time by your self.

In this time, we will give you global description about this  LiPo Battery Charger using LM324 IC like in Figure 1 below, beside we give you circuit schematic diagram and component parts used in this circuit.

Circuit Schematic Diagram

Component Parts

• LM7809 IC
• Resistors
• LM324 IC
• LED
• Diode
• Transistor
• LiPo Battery

Description

This is circuit schematic diagram of LiPo Battery Charger using LM324 IC that can help you to build LiPo battery charger. The main component in this circuit are LM324 IC.

According Circuitstoday site that also published this circuit describe that the heart of the circuit is an LM324 opamp. LM324 is a general purpose single supply quad opamp. You can use any single supply opamp in its place. I used LM324 because it was the only single supply opamp with me at that time. TL071, TL072 etc are other options. The LM324 is wired as a comparator here. The reference voltage is applied to the non-inverting input and it is set using resistors R1 and R2. The reference voltage here is 3.5V. It is obtained using the equation Vref=(9/(R1+R2))*(R1). The positive terminal of the battery is connected to the inverting input of the opamp through diode D1. R5 is just a pull down resistor.

When ever the battery voltage is above 4 volts the voltage fed back to the inverting input will be higher than 3.5 voltas. That is 4V-D1 drop =3.5V. The output of the opamp swings to ground and transistor Q1 will be switched OFF. This isolates the battery from the charging voltage and the battery remains safe. When the battery voltage is below 4V, the voltage fed back to the inverting input will be lower than 3.5V and the output of the opamp swings to positive saturation. This makes the transistor ON and the battery starts charging. Resistor R4 limits the charging current of the battery to 60 mA. The governing equation is (Vcc-VcesatQ1-Vb)/R4=Ib. Where Vcc is the supply voltage, VcesatQ1 is the collector-emitter voltage  of Q1 during saturation, Vb is the battery voltage when discharged, R4 is the current limiting resistor and Ib is the charging current. When substituted by values it is (9V-0.2V-2.7V)/100 ohm=61mA.