I am in need of some help designing my battery pack. I have a few concerns, mostly around charging.
My plans consist of using a microUSB boost converter to bring the voltage to 16.8V for charging. This will go into a balancing charging BMS board hooked to four 18650 LG MJ1's. The output from those will go to a buck converter to bring the voltage to 12V and be hooked into a USB-PD car chargers guts. If the design is right I should get my USB-PD charging capability, an ability to charge the batteries with a CV setup.
The CV setup has me worried. I have seen posts warning about the high amps a highly discharged 18650 pack can pull when charging on CV alone. Since I plan on really only charging at 5V 1A (boosted to 16.8V) or at max 2A (again, boosted), do I need to worry about that? I am by no means an electronics expert and that is why I am asking.
I've seen some posts suggest wiring a resistor in series with the BMS to lower the number of amps that could be pulled. Through my poor calculations, I figured the required resistance to be around 56 ohms. Is this required? I don't want to starve the batteries of charging capability unless I have to.
If you have any questions or ideas for my build let me know!
I said screw it, I will find out temps and potential problems with the circuit to hopefully answer some questions others like myself may have. These will be coupled to a 4S setup with LG MJ1 cells. Here are my purchases:
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