As per title really i am new to this and trying to learn! But I want to make sure there is certain things in place for this little adventure of mine! so to outline it simply,

1. It has to have protection! overcharge, undercharge etc
2. USB C interface to charge - possible to use micro USB B but C is preferred.
3. If possible make it so it can be charged and used at the same time!
4. Be suitably fast at charging 2 cells connected in parallel but only if safe to do so!

So with that in mind it will be 2 18650 batteries in parallel which ideally can be charged using a quick charge IC this is where I am stuck and have looked at lots of different power banks and ripped them apart to understand them better, watched way to MANY YouTube videos and come to the conclusion that majority are not exactly safe.

I ordered some charger boards on amazon, rubbish little things and was informed they will work but charging them is not possible whilst using a connected device.

This, although not a major issue is something I want to address but what I really want to know is the best IC's to pick to make a decent and safe circuit and could do with some help on that! One that i am almost certain i WILL be using is the DW01 as i have seen this in almost all of the powerbanks I have pulled apart.

A few on my list but that I am not sure of are a B205A - my understanding is that this chip will do some kind of isolation of the supply which leads me to believe it has something to do with how I would change the IC to allow charging and use of the charger?

The 4056 - which I understand is what deals with the charging itself, a common chip that I have seen a lot and another user did inform me it wouldn't be up to the task I want hence me wanting to look at other options.

Now some other chips i have seen are S28N but I cannot find a datasheet in English to understand it better one thing I do know is it gets HOT when charging two 18650 cells although that was its configuration so assume it to be "safe" per say, but I have had one burn itself out (I bought multiple of these)

Another chip I have seen is the LM324? I've looked at the data sheet for this and I'm slightly confused why they would be in a powerbank?

Next the final chip I have looked at which is confusing me is 1210 0b44, I cannot find any info on this chip?

So I suppose what I really want is help in picking the right IC's that would be suitable for my needs

 

The fact is that the voltage required to charge a LI cell is greater than the voltage it delivers. How else can power be forced into the cell?
So you can not expect to use a cell while it is charging. So forget that concept. It could be that a separate supply can provide power while charging.

 

was informed they will work but charging them is not possible whilst using a connected device.

Charge can't flow into and out of a cell at the same time. However, load current can be drawn from a suitably rated charger while the charger is also providing charging current.

 

Assuring the best SAFE charging scheme PLUS providing enough power for some other device would be complex. It makes more sense to have a separate power supply from the charging system.

 

Very delayed response from me, apologies for that!

So as i said before charging and using the speaker wouldn't be a major factor just something I did think about! easier to just forget that idea mind!

I'm now moving onto working on the design, moved over to a PAM8406 and the 8403 seems to be hard to get one that isn't a clone which in turn the past 3 delivery's I have had have all been some cheap clone that is just useless to me.

So I'm redesigning it and onto my next question!

I am getting a ground loop I think? Remember I'm still learning so not 100% on this!

In connecting the Pam8406 and Bluetooth module together from the same power source I am experiencing "noise" like a very low level hissing from the speakers, I decided to test with two different power sources and the problem was resolve, how would one tackle this? Is this a ground loop or do I just need to isolate the power supply to the Bluetooth module?

 

The first rule is to not have any current sharing in the power feeds. That means a separate wire from each module to the supply, both sides, positive and negative. That prevents current drawn by one from affecting the voltage to the other. Often that is called a "star point" scheme. If that is not enough, then the next thing is to add impedance at the frequency of the noise in series with the power feed to the module receiving the noise. Also a shunt that has a low impedance at the frequency of the nois,e across the power terminals.
Not simple, really, but fairly clear as to what needs to happen.
Worst case is separate filter sections in the power supply.