An year ago, I've shared a circuit of USB li-ion charger based on LM358opamp. The circuit had some problems as reported by commentators that inclide wrong direction of LEDs.
Features:
- Charging via mini-USB connector which is very common.
- Charging status display by LED
- Simple circuit by using opamp, resistor, and not by any complex dedicated IC or micro-controller.
- Charges completely drained (0V) battery packs.
- Max charging current 500mA(limited by USB supply), depending on battery.
Here's the corrected schematics and the board design of the circuit.
Update: https://www.circuitsdiy.com/usb-li-ion-charger-build
Boards are available for buying.
What software is this for 3D visualization of PCB?
It's done using Eagle3d and POV-Ray.
Hi Arup,
I am Nelson from Malaysia/Kuala Lumpur.
I am not a complete electronic wizard but I am a handy man in every ways.
Currently I am in the midst of making a small solar light as following:-
LED 1 set 40pcs -3.2-3.5V each - 6 sets.
Solar panel 1pcs - 7 Volt X 1W X 150mW - 6 or 8 pcs.
12 Voltage Lead acid or any rechargeable battery.
I would like to make night light-up with this 240 high bright LED.
To tell the truth. I am average in calculating, not much knowledge on components and don't really know how to begin.
Some information for you.:-
The circuit board for 40 LED will be on a 3" in diameter circle shape board.
Other components.... I am not sure?
Solar Panel 2.5" x 4" - 1 pcs.
There should be a light sensor with relay to enable battery usage at night.
Battery ...you recommend it. Lead asid 12V x 4.5 AH or any... as long it is not as car battery size.
To be frank... I would like to light up my Parents Tomb which I will be making from Glass and acrylic. I want it to be lighted up at night everyday.
Tell me how can we go about.
Give a shout by the "Wish a Circuit" form and we can discuss it.
hi
how could i change circuit for 3.7v 2.4a battery?(please help)
thanks
Replace the transistor to a higher Ice one.
Hello,
I've built your circuit just as you show in your schematic, with the exception that I'm using a barrel jack connector, and a 5V switching power supply purchased from Sparkfun.com. When I test the voltage coming from the part of your circuit that you use to charge the battery, it's reading 3.77 Volts...is this correct? I had a 'dead' (measure 0V) Nokia 3.6 battery and the circuit seemed to work. However, when trying to charge a newer Samsung 3.7V, it doesn't seem to work. When fully charged, the battery reads 3.99V. I put it back in the phone until it was about 3/4 full...which it then reads 3.79V. When I connect it to the charger, it doesn't seem to do anything. Is this because the charger is outputting less voltage (3.77V)?
I'm very new to electronics, so forgive me if this is a dumb question.
Thank you for sharing your circuit though, hopefully I can use it eventually.
Thanks!
The resistor values are critical. Use exact and not near valued resistors and it would work.
At full charge a 3.7V li-ion measures 4.0-4.2V, so it's no problem.
Demo: https://www.youtube.com/watch?v=wJ_uI1uWbes
I did use exact resistor values...however they have 5% tolerance...is that too high?
Is the following transistor ok?
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/SS8550DBU/?qs=%2fha2pyFadujt6F5VxVsILMAzTOoVTACO85s0WXtxwfWcIooqYaVsJw%3d%3d
(It's what I used)
Do you see anything wrong from the following picture? It's what I have on my breadboard:
http://domiflichi.hopto.org/images/LiIonChargerAttempt-sm.jpg
and plugged in:
http://domiflichi.hopto.org/images/LiIonChargerAttemptPluggedIn-sm.jpg
Hi,
The linked transistor is the same as used in the circuit.
Everything looks fine (I didn't analyzed circuit design which I assume you followed correctly).
5% tolerance is fine as the resistances remains constant when temperature is constant in these applications where resistors doesn't get heated.
Just check every resistor once in multimeter to be sure there are no faulty ones whose value is junk. There are two 2K resistances in board but 2K is not a popular value, you can replace by 2.2K (nearest one) but you need to use 2.2K in both places.
PS: Can I show your prototype (2nd image) in this website under user gallery?
Hi Arup,
I checked all the resistors with my multimeter and they appear to be fine. I did use actual 2K resistors (I bought them specifically for this circuit) on this prototype.
Any other ideas?
Yes, you may use my image on your website. Thanks for asking. 🙂
Thanks,
Jamie
The battery voltage is measured through R3-R4 voltage divider (the 2K ones). I suggest you replace R4 with a 2.2K pot and set the value to slight less than 2K. Then the circuit will charge the battery to a bit higher volatge. After some tries you'll reach to a specific value say 1.8K which will charge your battery to 4.2V(full charge). Then replace the pot with a fixed value resistor of that value.
Hi Arup,
I got your board in the mail and soldered everything on yesterday:
http://domiflichi.hopto.org/images/LiOnChargerProBoardPopulated1sm.jpg
However, I'm having a very similar problem as when using the breadboarded circuit. I still am using 2K resistors even though it says to use 2.2K resistors on the sheet that came with your board. (Not sure if this matters too much)
There are a couple of different things though: 1. I'm only getting 3.51 volts on the output side. 2. The charging LED (#2 - the one in the middle) never comes on. (On my breadboard it would at least come on a little bit and 'flash' just a little bit). 3. I'm providing power via a USB cable from my PC. (Not sure if that matters, but thought I would mention it)
Thanks!
Hi Jamie,
Sorry for late reply and Happy new year to you.
Now this thing is even confusing me. If you had it working on breadboard with same diagram as in the PCB, it will work the same as breadboard. Then you just had to calculate the new resistor value for your desired voltage and replace a 2K resistor.
2K, 2.2K both are fine.
Hi,
Is there anything specific about transistor used, S8550d ? These are not very popular in Poland, can I use any similar PNP transistor (with respect to its pinout) ?
Keep up Arup, thank you for sharing your projects to the community 🙂
Regards,
Michal I.
--cont--
I forgot to specify - when I meant similar PNP transistor i was thinking od BC557 or BD140
You can use any general purpose PNP transistor, just make sure they have enough current rating. For example, the S8550D is rated for 1.5A, while BC557 has 100mA and BD140 has 1.5A rating.
So, use BD140 and mind the pinout.
Hi,
thank you for this charging circuit. I just finished it with BD140 and 2.2k for R3,R4. Now I measure only 3.73V without battery connected from collector to ground.
How can I set charging voltage to about 4.2V?
Thanks,
Matthias
Just soldered a pot in fpr R4 at 1.8k and testing. The battery charges, my yellow led is on but not flashing? Any suggestions?
I guess you used yellow in place of blue LED.
Try altering the value of R8 to fix the issue.
thanks, works great
The charging led doesn't lit at all. What i done wrong?
i want to 40-0-40v dc 3amp from 12vdc .i have 3524 mos circuit,but need transfarmer data ,transfarmer should nt b heat nor mos should heat
Is it possible to make 12v ac 2A from 230v ac without transformer?
Hello.
I would like to use full power of s8550, it means a 1, 5 ampere charging current. I have strong 5V power supply, which can deliver about 2A of current. How can I change Your schematic, to obtain current of 1 to 1,5 ampere? I need such a high current, to charge high capacity 18650 Li-Ion cells. Thanks in advance for Your reply.
Hello,
can I use some other transistor like a 2n3904? as this transistor doesn't seem to be very common.
Hello I built the circuit exactly how you stated but i used a TIP2955 instead.
my output power was very low but when i removed LED 1 the voltage a lot more to what i would like. However i am only getting a 80mA out but i would like something a lot higher.
Is there anything you could suggest that could help me fix these problems please?
Thank you in advance
hi arup, first of all, congratulations and thanks for this schematic, it can be very usefull 4 all of us. 😀
I just have a question, i done this circuit on my breadboard, but my exit tension is something like 3,6v is this normal? that's because the finish led light up until my battery reach 100% of charge.. maybe 30% or 40%... I've read somewhere on internet that this chargers has a 4,2v and 10% of the current on output... I'm alone-home-learning electronics and hope your help for my project.. by the way, my batteries are 2x 3,7v 3000mah parallel connected.
Thanks you!
Thumbs up from Portugal!
i changed my r4 to aproximately 1,4k and my output tension is 4,12v seems like to be alright, now the two batteries are charging and i'll till tomorrow to check if they charged properly... my only problem now is the charging led not flash, just light up static...
Best Regards!
how can i control the charging current & voltage for 8.4v?