Li-Ion Charger Using Max 1555

[samkim]

Hi Friends,

I am new to this forum, well I am trying to make a Li-Ion charger using Max 1555, has any one tried out doing this, if so please do tell me, I have been unsuccessful many a times doing this experiment. I am enclosing the circuit used for this experiment.I have done all the circuit connections as shown in the diagram but still when the battery has been charged after being discharged till 3.55V, while charging the LED will be in ON state, when it reaches the maximum(4.15V), the LED has to turn off, but in my case it remain to be ON. Could any one know the exact reason behind this.I am using DC input instead of USB for charging.Is it okay with it.Thank You.

[samkim]

hi friends,

I need help regarding this matter.Does any one, if they would have done the similar kind.Please help me .Thank You.

[EWorkshop1708]

Have you downloaded the datasheet for the Maxin1551/1555 chips?

I've built a few circuits with them, and they are excellent IC's.

To answer some of your questions.......

The LED pin on the 1555 is Active low. You need to use a ~330 ohm resistor from 5V going to the LED anode, and the LED cathode goes to the LED pin on the 1555. If you are using both USB and DC inputs, you can have two LEDs. I noticed in your schematic, your LED is incorrectly connected to the Li-Ion battery, that's why your LED is staying on.

Even though the datasheet calls for only 1uf, try a bigger capacitance on the 5V inputs, and the 1555 chip is more stable. I like to use over 100uf, but that's up to you.

The 1555 shuts the LED off around 4.15V, but it will trickle charge the battery up to full 4.19-4.23V (depending on temperature)

[samkim]

Hi Friends,

Thanks For the reply from EIYWorkshop1708 and all the views made for my topic.Well Let me confirm once again i am doing this Li-Ion Charger Using Max 1555 project.I wanted to specify one more thing that the Li-Ion Battery I am using is NOKIA's BL-5C/6600/3650 3.7V used for lower end mobile phones like NOKIA 6030.Is this right one is my question.

TO EIYWorkShop1718,

Well Thanks for your reply,before doing this experiment, I had a few doubts , so i wanted to confirm with you.

1. According to the circuit diagram given by me to the forum, I am connecting Anode of LED to Pin No 5(BATT) and the other end (cathode) to 330 ohm resistor and the other end of resistor to Pin No 3 (CHG_STAT).

2. As answered, you say that LED is incorrectly connected to the L-Ion Battery.I had a doubt so wanted you to confirm me.Now as you say I should connect one end of resistor to Pin No 4 (DC) and the other end of resistor to the Anode of LED and cathode of LED connected to Pin No 3(POK bar or CHG bar).Am I right with what u have said to me.Its just a confirmation that this is what you meant to say to me.

3. You also said to increase the capacitance value from 1uf to 100 uf or even more.Presently I am using 1uf (disc or ceramic ) capacitor, if at all if the increase the value of the capacitor shall i use the same ceramic(disc) or electrolytic capacitor.

Thank You.

[sivan_and]

how did u connect the charger output to the Li-ion pack ? did u remove the small circuit attached with the cell phone battery ?

[EWorkshop1708]

Originally posted by samkim

2. As answered, you say that LED is incorrectly connected to the L-Ion Battery.I had a doubt so wanted you to confirm me.Now as you say I should connect one end of resistor to Pin No 4 (DC) and the other end of resistor to the Anode of LED and cathode of LED connected to Pin No 3(POK bar or CHG bar).Am I right with what u have said to me.Its just a confirmation that this is what you meant to say to me.

3. You also said to increase the capacitance value from 1uf to 100 uf or even more.Presently I am using 1uf (disc or ceramic ) capacitor, if at all if the increase the value of the capacitor shall i use the same ceramic(disc) or electrolytic capacitor.

Thank You. [/B]

Your Welcome.

You have it correct in #2. Confirmed. 5V feeds the LED through the resistor, and the IC LED pin basically provides a negative path to ground for the LED.

And #3 Also, if you have a 1uf disc capacitor, just add the extra capacitance in parallel. Use an electrolytic capacitor, you can get them in small sizes for low voltage. It helps out if you have any fluctuations in the power supply. I noticed the LED may turn on/off or it restarts charging cycle, or completes early without clean power. That's why I recommend 100uf+ You don't have to add more, it's up to you, but I find it does help some.

[samkim]

TO EWorkShop1718,

Thanks for your wonderful help.I followed the procedure which you had told but only using 1uf disc cap.It worked out.The LED would go to OFF state as soon as it reached(4.13 V). I am really happy.
Thank You.

[luketanti]

Hello. I do not know if some one will reply to this but I followed all the instructions and the LED is still lite when the Battery reaches 4.14 volt. I left it all night long and the next morning the LED was still on and the voltage was the same 4.14 volt. What is the problem with this?? I tried 5 more max1555 chips and all the same result. Please if anyone can help reply. Thanks

[macnomad]

from looking at the previous posts, I would try flipping the polarity of your indicator LED