on video Battery Low | 50% Charged | Fully Charged..Automatic 3.7V Battery Charger

Battery Low | 50% Charged | Fully Charged..Automatic 3.7V Battery Charger

Welcome to my channel "Tech help" here you will learn how electronics is work..Here you will also learn to make diy electronics circuits, handmade crafts, new inventions, mechanical, computer software..Here you will find lots of electronics projects and handmade circuits..

Friends in this video we will learn how to make 3.7v automatic battery charger..It is a 3.7v battery charger with 3.7v battery level indicator circuit..

The advancement in Electric Vehicles, Drones and other mobile electronics like IoT Devices seems to be promising for the future. One common thing among all these is that they are all powered by batteries. Following Moore’s law the electronic devices tend to become smaller and more potable, these portable devices should have their own source of power to operate. The most common battery choice for portable electronics today is Lithium Ion or Lithium Polymer Batteries. While these Batteries have a very good charge density they are chemically unstable under harsh conditions hence care should be taken while charging them and using them.

In this project we will build a Two Stage Battery charger (CC and CV) that could be used as to charge Lithium ion or lithium polymer batteries. The battery charger circuit is designed for 7.4V lithium battery pack (two 18650 in Series) which I commonly use in most robotics projects but the circuit can be easily modified to fit in lower or slightly higher battery Packs like to build 3.7 lithium battery charger or 12v lithium ion battery charger. As you might know there are ready made Chargers available for these batteries, but those that are cheap are very slow and those that are fast are very expensive. So in this circuit I decided to build a simple crude charger with LM317 ICs with CC and CV mode. Also, what’s more fun than building your own gadget and learning in it’s process.

Remember that Lithium batteries should be handled carefully. Overcharging it or shorting it might lead to explosion and fire hazard, so stay safe around it. If you are completely new to lithium batteries then I would strongly advise you to read through the Lithium battery article, before proceeding further. That being said let’s get into the project.

  CC and CV Mode for Battery Charger

The Charger that we intend to build here is a Two Step Charger, meaning it will have two charging modes namely Constant Charge (CC) and Constant Voltage (CV). By combining these two modes we will be able to charge the battery faster than usual.

Constant Charge (CC): The first mode to get into operation will be the CC mode. Here the amount of charging current that should enter the battery is fixed. To maintain this current the voltage will be varied accordingly.

Constant Voltage (CV): Once the CC mode is completed the CV mode will kick in. Here the voltage will be kept fixed and the current will be allowed to vary as per the charging requirement of the battery.

In our case we have a 7.4V Lithium battery pack, which is nothing but two 18650 cells of 3.7V each is connected in series (3.7V + 3.7V = 7.4V). This battery pack should be charged when the voltage reaches down to 6.4V (3.2V per cell) and can be charged up to 8.4V (4.2V per cell). Hence these values are already fixed for our battery pack.

Next we have decided the charging current in CC mode, this can normally found in the datasheet of the battery and the value depends on the Ah rating of the battery. In our case I have decided a value of 800mA as Constant Charging current. So initially when the battery is connected for charging the charger should get into CC mode and push in 800mA into the battery by varying the charging voltage accordingly. This will charge the battery and the battery voltage will start to increase slowly.

Since we are pushing a heavy current into the battery with higher voltage values we cannot leave it in CC till the battery gets fully charged. We have to shift the charger from CC mode to CV mode when the battery voltage has reached a significant value. Our battery pack here should be 8.4V when fully charged so we can shift it from CC mode to CV mode at 8.2V.

Once the charger has shifted to CV mode we should maintain a constant voltage, the value of constant voltage is 8.6V in our case. The battery will drain a significantly less current in CV mode than CC mode since the battery is almost charged in CC mode itself. Hence at a fixed 8.6V the battery will consume less current and this current will go reduce as the battery gets charged. So we have to monitor the current when it reaches a very low value say less than 50mA we assume that the battery is fully charged and disconnect the battery from the charger automatically using a relay.

To summarize we can list the battery charging procedure as follows

Enter CC mode and charge the battery with a fixed 800mA regulated current.

Monitor the battery voltage and when it reaches 8.2V shift to CV Mode.

In CV mode charge the battery with a fixed 8.6V regulated voltage.

Monitor the charging current as it gets reduced.

When the current reaches 50mA disconnect the battery from charger automatically.

The values, 800mA, 8.2V and 8.6V are fixed because we have a 7.4V lithium battery pack. You can easily change these values as per the requirement of your battery pack. Also note that there exist many stage chargers. A two stage charger like this is the most commonly used one. In a three stage charger the stages will be CC, CV and float. In a four or six stage charger the internal resistance, temperature etc will be considered. Now, that we have a brief understanding of how the Two step charger should actually work, let’s get into the Circuit Diagram.

The complete circuit diagram for this lithium battery charger can be found below. The circuit was made using EasyEDA and the PCB will also be fabricated using the same.

As you can see the circuit is pretty simple. We have used two LM317 Variable voltage regulator ICs, one to regulate Current and the other to regulate Voltage. The first relay is used to switch between CC and CV mode and the second relay is used to connect or disconnect the battery to the charger. Let’s break the circuit into segments and understand its design.

The LM317 IC can act as a current regulator with the help of a single resistor. The circuit for the same is shown below

For our charger we need to regulate a current of 800mA as discussed above. The formula for calculating the value of resistor for the required current is given in datasheet asIn our case the value of current is 0.8A and for that we get a value of 1.56 Ohms as the resistor value. But the closest value we could use is 1.5 Ohms which is mentioned in the circuit diagram in previous step.

For the CV mode of lithium battey charger we have to regulate the voltage to 8.6V as discussed earlier. Again LM317 can do this with the help of just two resistors. The circuit for the same is shown below.

Battery Low | 50% Charged | Fully Charged..Automatic 3.7V Battery Charger

Welcome to my channel "Tech help" here you will learn how electronics is work..Here you will also learn to make diy electronics circuits, handmade crafts, new inventions, mechanical, computer software..Here you will find lots of electronics projects and handmade circuits..

Friends in this video we will learn how to make 3.7v automatic battery charger..It is a 3.7v battery charger with 3.7v battery level indicator circuit..

The advancement in Electric Vehicles, Drones and other mobile electronics like IoT Devices seems to be promising for the future. One common thing among all these is that they are all powered by batteries. Following Moore’s law the electronic devices tend to become smaller and more potable, these portable devices should have their own source of power to operate. The most common battery choice for portable electronics today is Lithium Ion or Lithium Polymer Batteries. While these Batteries have a very good charge density they are chemically unstable under harsh conditions hence care should be taken while charging them and using them.

In this project we will build a Two Stage Battery charger (CC and CV) that could be used as to charge Lithium ion or lithium polymer batteries. The battery charger circuit is designed for 7.4V lithium battery pack (two 18650 in Series) which I commonly use in most robotics projects but the circuit can be easily modified to fit in lower or slightly higher battery Packs like to build 3.7 lithium battery charger or 12v lithium ion battery charger. As you might know there are ready made Chargers available for these batteries, but those that are cheap are very slow and those that are fast are very expensive. So in this circuit I decided to build a simple crude charger with LM317 ICs with CC and CV mode. Also, what’s more fun than building your own gadget and learning in it’s process.

Remember that Lithium batteries should be handled carefully. Overcharging it or shorting it might lead to explosion and fire hazard, so stay safe around it. If you are completely new to lithium batteries then I would strongly advise you to read through the Lithium battery article, before proceeding further. That being said let’s get into the project.

  CC and CV Mode for Battery Charger

The Charger that we intend to build here is a Two Step Charger, meaning it will have two charging modes namely Constant Charge (CC) and Constant Voltage (CV). By combining these two modes we will be able to charge the battery faster than usual.

Constant Charge (CC): The first mode to get into operation will be the CC mode. Here the amount of charging current that should enter the battery is fixed. To maintain this current the voltage will be varied accordingly.

Constant Voltage (CV): Once the CC mode is completed the CV mode will kick in. Here the voltage will be kept fixed and the current will be allowed to vary as per the charging requirement of the battery.

In our case we have a 7.4V Lithium battery pack, which is nothing but two 18650 cells of 3.7V each is connected in series (3.7V + 3.7V = 7.4V). This battery pack should be charged when the voltage reaches down to 6.4V (3.2V per cell) and can be charged up to 8.4V (4.2V per cell). Hence these values are already fixed for our battery pack.

Next we have decided the charging current in CC mode, this can normally found in the datasheet of the battery and the value depends on the Ah rating of the battery. In our case I have decided a value of 800mA as Constant Charging current. So initially when the battery is connected for charging the charger should get into CC mode and push in 800mA into the battery by varying the charging voltage accordingly. This will charge the battery and the battery voltage will start to increase slowly.

Since we are pushing a heavy current into the battery with higher voltage values we cannot leave it in CC till the battery gets fully charged. We have to shift the charger from CC mode to CV mode when the battery voltage has reached a significant value. Our battery pack here should be 8.4V when fully charged so we can shift it from CC mode to CV mode at 8.2V.

Once the charger has shifted to CV mode we should maintain a constant voltage, the value of constant voltage is 8.6V in our case. The battery will drain a significantly less current in CV mode than CC mode since the battery is almost charged in CC mode itself. Hence at a fixed 8.6V the battery will consume less current and this current will go reduce as the battery gets charged. So we have to monitor the current when it reaches a very low value say less than 50mA we assume that the battery is fully charged and disconnect the battery from the charger automatically using a relay.

To summarize we can list the battery charging procedure as follows

Enter CC mode and charge the battery with a fixed 800mA regulated current.

Monitor the battery voltage and when it reaches 8.2V shift to CV Mode.

In CV mode charge the battery with a fixed 8.6V regulated voltage.

Monitor the charging current as it gets reduced.

When the current reaches 50mA disconnect the battery from charger automatically.

The values, 800mA, 8.2V and 8.6V are fixed because we have a 7.4V lithium battery pack. You can easily change these values as per the requirement of your battery pack. Also note that there exist many stage chargers. A two stage charger like this is the most commonly used one. In a three stage charger the stages will be CC, CV and float. In a four or six stage charger the internal resistance, temperature etc will be considered. Now, that we have a brief understanding of how the Two step charger should actually work, let’s get into the Circuit Diagram.

The complete circuit diagram for this lithium battery charger can be found below. The circuit was made using EasyEDA and the PCB will also be fabricated using the same.

As you can see the circuit is pretty simple. We have used two LM317 Variable voltage regulator ICs, one to regulate Current and the other to regulate Voltage. The first relay is used to switch between CC and CV mode and the second relay is used to connect or disconnect the battery to the charger. Let’s break the circuit into segments and understand its design.

The LM317 IC can act as a current regulator with the help of a single resistor. The circuit for the same is shown below

For our charger we need to regulate a current of 800mA as discussed above. The formula for calculating the value of resistor for the required current is given in datasheet asIn our case the value of current is 0.8A and for that we get a value of 1.56 Ohms as the resistor value. But the closest value we could use is 1.5 Ohms which is mentioned in the circuit diagram in previous step.

For the CV mode of lithium battey charger we have to regulate the voltage to 8.6V as discussed earlier. Again LM317 can do this with the help of just two resistors. The circuit for the same is shown below.