Hello, My name is Wan. My focus research area is on Battery chargers. I would like to know the part for Constant Current charging. As i have done a simple circuit for the cut-off battery charger system without constant current. As I have conducted a few testing for the current control it is not constant at all. I am going to charge a 48V 8Ah battery lithium-ion. The charging mechanism should be CC then CV during the end of the charging.
I'm using a rectifier AC-DC as input with a regulator for 56V and a voltage cut-off circuit with a current limiter. However, the current limiter is not working as i try to maintain at 3A the current drops while charging. Besides, i have tried LM338 as a current limiter also, the result is still not constant unless using led it is constant. The input voltage is 56V and the OP-AMP 741 will compare the input if the battery is fully charged at 54V so the OP-AMP will cut off. It is set up by varying the trimmer pot to 54V. My consent is for constant current at 3A, can anyone share with me how to make it constant at 3A. I am very happy if you can share with me tips or fundamentals for Constant Current Charging/battery charger.
Dear Wan Muhamad Hakimi Bin Wan Bunyamin
To achieve constant current charging for your 48V 8Ah lithium-ion battery, you can use a current regulating circuit in addition to the voltage cut-off circuit you have already designed.
One way to implement constant current charging is by using a current regulating IC such as LM317 or LM350. These ICs have an adjustable output voltage and a current limiting function that can be used to regulate the charging current.
Here is a simple circuit using LM317 that can be used for constant current charging:
By using this circuit, the LM317 will regulate the charging current to the desired value (in this case, 3A) as long as the input voltage is high enough to provide the required power to the circuit. The voltage cut-off circuit you have designed can be used to terminate the charging when the battery voltage reaches the desired level (in this case, 54V).
Please do let me know if it works.
Take simple 0-30V (or required voltage), 5A(or required current rating) power supply. Set the voltage to required value. Then Short circuit the power supply by wire. Then using current control knob, set constant current which you want to use. Then, remove short circuit. Now connect your battery to be charged, it will get charged by constant current set by you as above. Once battery reaches near full charge condition, it will come out of constant current mode and will move to constant voltage mode where current will start dropping towards zero value
LM317 input voltage is 4.25-40V. The output current is 0.01-1.5A. Can this IC regulate the charging current?
This is the circuit that I have drawn based on your descriptions. So the potentiometer is important the adjust the output current? Kaushik Shandilya
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Metals
- Alloys
- Steel