Hi, I am new to KICAD. Can you please tell me how REG25 and REGIN (the one with red circles) are connected ? and how to connect them ?
Not sure what your KiCad specific question is ? if it’s a general electronics question you would be better served at a general Electronics forum:
etc.
These are voltage levels, you connect them as you would any other voltage level, e.g. 5V, 3.3V etc.
In the schematic editor you would create a “label” of that name (keyboard shortcut “L”, or right-click context menu, or an icon), and place it where you have circled things.
You would also create labels of the same names and place them at pins 6 and 7 of your IC. By naming these nets with labels, this tells KiCad they are connected (without having to draw difficult to follow wires)
They look like regular local labels to me. See also this section:
The parts you encircled just have an “extra” horizontal wire that makes them look a little bit like a power symbol.
Ah okey thanks for the clarification, I tried to use power symbols and simulate the model, here is the error I got :
where the U1 is the yellow bloc which I already added to the library and its the same component w"ve been talking about
Thanks for the information, when I tried to simulate the circuit I’ve made before I go to the routing step, I am getting this error:
DO you have any idea how to resolve this question ? knowing that I’ve download that circuit before which is BQ35100PW.
Your schematic looks … sub optimal 
It’s a mess of wires, with some passives thrown in at seemingly random places. In the original posted schematic, the IC is drawn with all pins in pin order, wich is also not very good, but at least the passives around it are organized in a comprehensible manner. It’s quite important to draw schematics in a form that puts emphasis on how the circuit works and the function of each symbol in it. With the schematic you have created there are probably not many people attempting to untangle the wires to get some comprehension.
For the other screenshot. You got the error message:
No simulation model definition found for symbol ‘U1’.
The schematic symbol (the yellow thing you see in the schematic) is something different then the simulation model. If you want to simulate the schematic you will need both, and you will have to add the simulation model for your IC to the schematic symbol. You can do that in the symbol properties of the schematic symbol. I do however not know whether there is a simulation model for the BQ35100 that is compatible with ngSpice, or where to get it.
Thank you so much for the clarification, here’s an updated version of the circuit, any advice regarding this one ?
This is a direct copy from the TI datasheet PDF and its on the first page, did you know that please? if you do then you need to continue reading or if you dont then I would start to read it.
There is little we could do any different than that at this point 
Hi, Can you please tell me what do you mean by TI?
Ah! Yes, I know that and I am trying to make a PCB for that circuit to measure the current provided by a solar panel while charging a battery! So, I think that the first step is to make the BQ35100 works and to do that I have to make the circuit that is the on datasheet to :
1-Power the BQ35100
2-Connect it via I2C to a µC
3-Connect the battery with the alert function
So, that’s why I am trying to do right now.
I think you should concentrate on getting it to work on a breadboard before worrying about making a PCB. Your idea of running a simulation shows that you don’t understand what you are up for. If I were you I’d test the reference circuit on a breadboard (you can get SOIC to DIP adaptors) using an Arduino or similar platform to communicate with it, using a library like this one:
This looks like a breadboarding and software project, and not much to do with KiCad.
The problem is that I don’t have the BQ35100 right now, so I am trying to make the circuit before sending it to JLCPCB to place the components and send me back the pcbs.
BQ35100 is a LCSC extended part, which I think means there are minimum order quantities, even if you only want one board made, and IIRC you have to buy 10 boards before JLC will assemble all of them, otherwise they just assemble one (or is it two) and send you the rest of the parts.
Unfortunately the TI evaluation module is quite expensive and I don’t see any third party evaluation modules.
As @retiredfeline states: this thread has little to do with Kicad. Sourcing and design use of components is outside the purpose of this forum.
This thread will close in one hour unless questions on the use of Kicad are asked.
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How can I verify that BQ35100 is an LCSC extended part ? I think I need 5 pcs, If I order 5 pcs and they sent me the rest of the parts separately, it will cost less than the BQ35100 that TI are selling, don’t you agree with me in that point ?
I’m sorry @Zaki23Madrid , your question has absolutely nothing to do with Kicad.
Your questions are far better asked in the forums @RaptorUK suggested way up in this thread. This Kicad forum is for question relating to the use of Kicad.
You are most welcome to return when you have questions relating to the use of Kicad.
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