Need help with my li-ion charger circuit with 5V output.

Hi
I need your opinions and help about my circuit design. Here below is my projects charger part scheme. I am not a electronic engineer and not much experienced in electronics so i advised by an EE during design.
Circuit using TI's BQ24618 IC. Datasheet



I want to use this circuit to charge 4s2p Li-ion (3.7V 3000mAh samsung 18650 * 8 Li-ion batteries so 14.8V and 6000mAh) battery pack with 20V 2A wall adapter. Battery pack has included protection PCM.
I printed and soldered PCB. Here is my problems.
Charger circuit acting as charging. green led (stat1 ) and blue led (PG) on. But never complete charge after hours (theoretically green led get off and red led - stat2 - get on when charge completed is not it? ) Also the circuit was cold during all charging process so i think cirucit is not working.

Then I realised the resistance RP22 is wrong. RP22 must be arround 700K for charging 4 cell . I tought that i designed the circuit wrong and this circuit can be use for 3 cell li ion. So i tried to charge a 3s2p li ion battery pack. That time i quess circuit is working. A little heat on circuit. After a couple hours green and blue light started to blink. So I thought the circuit is failing again am I wrong ?

Also circuit has a LM2476-5.0 part with usb output for charging cell phones or etc.


When i attached battery pack to Circuit it seems i can get 5v from USB output. I can power up an arduino or teensy. But i can not charge an iphone from USB ? What can be cause problem?

Can you please evaluate the circuit design and give me advices? Any advices, opinions, helps needed.

Thank you very much.

But i can not charge an iphone from USB

Click to expand...

Li-ion batteries are popular but they need caution when charging. Look for news reports about them causing fires and explosions.

To get an experienced answer, you need to hear from someone with experience with the BQ24618 IC.

Did your Iphone come with a charger? Do you think you can make a better charger?

The risk of Li-ion type makes it risky to construct a homebrew charger. If I were to do so, I don't think I would use a control IC. IC's are easy to ruin the first time we use them. It's easy to do the wrong thing by mistake.

I think I would try to make my foolproof charger: (a) from few parts, (b) which I know exactly how they behave, and (c) cannot go above a safe charge rate, and (d) which cannot go higher than a maximum safe voltage. Possibly a simple zener diode regulator for each individual cell. The reason is because it's difficult to make certain that multiple cells are getting equal charge.

I guess it would take longer to charge all my batteries, but you can't always have everything when you homebrew.

Thanks. i handled usb output. I think the charger circuits problem is about input current now.

Hey @judasdsc79, could you make the IC work?

I'm struggling with the same IC. I tried two different designs based on the datasheet's schematics but I can't make it charge properly, I also had some MOSFETs blown-up....:sad:

what was your experience finally?

Best Regards