Hello,

My name is Aiman. My focus research area is on Battery chargers. I would like to know the part for Constant Current charging. As i have done a sample circuit for the CC-CV battery charger system.

I have conducted a few testing and simulation for the circuit but did not achieve CC-CV profile in the simulation. I am going to charge a 3.7V 3A 5000mAh battery. The charging mechanism should be CC then CV during the end of the charging. I'm using LM317 component to achieve constant current source circuit. TL431A acts a temperature compensated variable or adjustable Zener diode.

The input voltage is 12V and 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.

 

hi Arc3,
Look through the application section of these two PDF's, one is for the 78xx series, which may help.

Are you using LTSpice just for drawing the circuits or actually simulating?
Your post circuit has no Common Node.

Please post your asc file.
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hi eric,

Thank you for replying, i am using LTSpice to simulate the circuit. Below is the asc file.

 

hi Arc,
This is my version of the circuit using the standard LTS models.

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hi Arc,
This is your circuit modified driving a 3.7V Li-ion cell from a 50% state of charge. SOC = .5
Needs a design improvement.

Battery current in Blue
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hi eric,

Thank you for the modified circuit. Can you provide me the component library that you use for your circuit as I want to try simulate it as well. thanks in advance

 

hi Arc.
A zip file with some of the components.
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Hi Arc,
A couple of sim circuits that maybe useful for your circuit development trials.
X-axis in Hours
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Below is the circuit, modified to give a CC CV output with some realistic values:
(For example, you can't get 3A through a 6.25Ω resistor (R1) with a 12V supply, and the LM317 is only good for about 1.5A)

 

Vin is 12V, Vout is 3V, the difference is 9V at 3A is 27 watts. Where are you going to dump the power?
I think a switching power supply would do the job with 1W of power loss.

I can't remember how to add current limiting to this. Or just the LM2576 which limits at about 3A.

 

hi Arc.
A zip file with some of the components.
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Hi Eric,
Sorry, but i am having problem running the circuit given as the NPNdarlington.lib could not be opened. I am new to the LTSpice software.

 

Sorry, but i am having problem running the circuit

It wouldn't do much good as that is not an operating circuit that will do what you want.
Look at my posted circuit to see what you need to change.

What is the purpose of U2 and Q2 as there connection makes no sense?

 

I used the LTM8026 battery charger. It will not waist 27 watts of heat. I made the cap-battery much smaller because my computer is old like me and runs slow. 2.9A and 3.6V.

 

It wouldn't do much good as that is not an operating circuit that will do what you want.
Look at my posted circuit to see what you need to change.

What is the purpose of U2 and Q2 as there connection makes no sense?

hi crutschow,
Thank you for replying. I see that you are using LT1084 instead of LM137 right. Can i ask the purpose of using this component instead of the LM137?

 

the purpose of using this component instead of the LM137?

The LM317 is only good to about 1.5A and you said you wanted 3A.
The LT1084 can go to 5A.

 

The LM317 is only good to about 1.5A and you said you wanted 3A.
The LT1084 can go to 5A.

Hi Crutschow,

i have constructed and try to simulate your circuit. However, i did not get the same result as yours. Can you look at my circuit and possibly tell me what is wrong with my circuit or components i used?

 

Hi Arc,
You need these .include on your circuit diagram.
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Update:
The sub, lib, mod files should be placed in the LTSpice lib folder, this shows my Path.

C:\Users\ericg\Documents\LTspiceXVII\lib

 

Hi Arc,
Checking your @crutschow asc file you have an incorrect .tran setting, refer this image.
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BTW: I had to use my pot and TL431 models, otherwise it works as expected.

 

The LM317 is only good to about 1.5A and you said you wanted 3A.
The LT1084 can go to 5A.

Hi Crutschow,

thanks for helping me with the modified circuit recently. I want to ask the options i have if i want to upscale my circuit to charge 12V battery with 1-3A current. Do i need to replace any component or do i have to change the value of my resistors. Also i could not find any LT1084 in my place hence, what are the other option can i replace the component with?

 

Hi Crutschow,

thanks for helping me with the modified circuit recently. I want to ask the options i have if i want to upscale my circuit to charge 12V battery with 1-3A current. Do i need to replace any component or do i have to change the value of my resistors. Also i could not find any LT1084 in my place hence, what are the other option can i replace the component with?

I change the LT1084 to LM338 as a replacement. I intended to charge 12V battery with 1A current. Why does the voltage drop massively from 12V supply to 3V on the output?