I was working on designing a single-cell Li-Ion MPPT solar charger PCB. I am relatively new to PCB design and was struggling understanding why most PCBs, like the "Sunny Buddy" linked below, use resistors with really small power rating values (typically 1/4W) that seemingly don't correlate to the input voltage and current.
I wanted to test my PCB design with a breadboard before I finalized any component choices so I was wondering if anyone could explain why the resistors chosen have really small power ratings, because to my understanding based on the description of the Sunny Buddy with a 20V max input and a 450mA charge current that is around 9 watts of power going through the board which the resistors definitely would not support.
I feel as if the answer is right in front of me and very simple but it is just not clicking yet. Any clarification or help would be greatly appreciated. Thank you.
Sunny Buddy link : https://www.sparkfun.com/products/12885