Hi Steve,
I am not planing to outsource my project to anyone. If that's a case, I would have done it long a go. I am here to clear my doubts, and learn something. My question was:
* How to charge 2 cell (18650 x 2) batteries (3.7v & 3800mAh)
* How to step-up the voltage (convert 3.7v to 5v)
* How to indicate the battery status (to indicate the voltage to the user using few LEDs)
Lighter note: I wish my lecturers were more supportive, unfortunately they are not.
Actually I came up with a small indicator circuit (using Zener diodes) and did the simulation on Proteus software. It look fine to me, I would like know expertise opinion on this..
Please see attached image for your reference.
Well, I did some homework before posting this question on this forum. I also watched many Youtube videos as well. Also learned about 3 stage charging of Lipo/Lit-ion batteries.
The Raspberry Pi-3 (it has a bluetooth and Wifi therefore it draws more current compare to previous versions) requires 5v (5.1 or .2 volts will do) and it draws 2A to power the system. And as you know, Lit-ion (18650) battery has 3.7V and the maximum charging will be 4.2V and it will be discharged current flow at that point, if I am not mistaken. I have done some practical test using $1 module. But it took me forever to charge the batteries, perhaps I used a low ampere charger..
My plan is to connect two 18650 batteries parallel mode to get more Amp-hours, so I can keep the Pi on for a long time. The battery output will be 3.7 volts but it will have 7600mAh, if I am not wrong.
I need a circuit design to charge these two battery at once, simultaneously, rather than charging each batteries one by one.
Why Fast charging?
As I mentioned before, the $1 module takes a long time to charge one battery (almost 3-4). I think it releases 800 - 1000mA current to the battery. What if we (perhaps "I") increase the current flow?
Power-supply
I will be using power-supply 5v, 2A USB charger
Many thanks,
Raiz
