Simple Li-ion Battery Charger Circuit using IC LTC4056

In this blog we will talk how to make a Simple Li-ion Battery Charger Circuit using IC LTC4056

We have used one special chip name LTC4056 and this chip control charging and stop when battery is full.

To make chip work we have used only few parts in this circuit.

This article show step by step way how to make this charger circuit.

What is Li-ion Battery Charger Circuit with LTC4056:

LTC4056 IC is made for charging Li-ion and LiPo batteries.

It is small, simple and good for charging many type of rechargeable batteries.

Below we can see easy circuit design using LTC4056 for charging one Li-ion battery.

Circuit Working:

Parts List:

IC LTC4056 can take input voltage from 4.5V to 6.5V and this circuit gives fixed output voltage of 4.2V and maximum current it gives is 700mA.

Here is some simple information:

• Input Voltage (Vin): 4.5V to 6.5V
• Output Voltage (Vout): 4.2V
• Max Output Current (Iout): 700mA

There is one resistor R2 and one capacitor C2 and these two parts control how long the timer will run.

We can choose value of R2 and C2 using this formula:

T = 1.1 × R2 × C2

where:

• T is time
• R2 is resistor in ohms
• C2 is capacitor in farads
• 1.1 is a fixed number used in formula

R2 and C2 are very important to set how long charging will go.

To get right charging time we can use correct values of R2 and C2.

One more capacitor C1 is also used as it keeps voltage stable during charging.

When picking value of C1 we need to think about our power supply and what our circuit needs.

One LED is added to show charging is happening.

LED will turn ON when charging and when battery is full and timer is finished LTC4056 stops charging and LED goes OFF.

LTC4056 also has one CHARG pin and when no power is coming in then this pin becomes high resistance and this helps protect battery and the circuit.

For more exact part values and details check LTC4056 datasheet.

This chip makes it easy to build and run a simple Li-ion battery charger for one battery cell.

How to Build:

Below are simple steps to make Li-ion battery charger using LTC4056 IC:

First put the LTC4056 IC on breadboard or PCB.

Be sure power pin and GND pin of IC are connected to power and ground properly.

Connect positive wire of power supply to Vin pin of LTC4056.

Connect negative wire to GND pin.

IC LTC4056 will give 4.2V output for charging.

There is no need to set this, it is already inside the chip.

Now connect PNP transistor between battery and LTC4056.

Check datasheet to find correct pin on IC for connecting transistor base.

Transistor gives current to battery.

To control current which is max of 700mA we can use base resistor R1 by using this formula:

R1 = VBE / Idesired

• VBE is base-emitter voltage which is about 0.7V
• Idesired is the charging current we want

For setting charge time use resistor R2 and capacitor C2.

And use formula:

T = 1.1 × R2 × C2

This gives timeout time T.

Choose R2 and C2 values based on how long we want battery to charge.

Add capacitor C1 to input side to keep voltage stable during charging.

Pick C1 value based on our power source and what the circuit needs.

Add LED with small resistor to show charging status.

LED ON = charging

LED OFF = charge done means IC goes to shutdown mode

Be sure CHARG pin of LTC4056 goes into high resistance (high impedance) when there is no power.

This protects battery and circuit when power is OFF.

Connect PNP transistor to single cell Li-ion battery.

Use correct values for current and timer to safely charge the battery.

Before using, test the charger with battery to check if charging and timeout works properly.y charger.

Conclusion:

This Simple Li-ion Battery Charger Circuit using IC LTC4056 is easy, works good and charges one cell Li-ion battery in correct way.

It is good to check LTC4056 datasheet and application notes to find correct part values and other important things based on our project need.

Always follow safety rules and standards for using Li-ion batteries.

References:

Linear Li-Ion Charger with Termination in ThinSOT