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Generally, the only parts that should need cooling are precharge FETs and resistors, DC-DC module, Raspberry Pis (maybe), Solar MPPTs, lights boards, batteries, etc.

Any parts that produce over 1W or so should require further evaluation for heatsinking or better component selection. The 1W number is not precise, and changes a lot based on package size, with larger packages having a lower thermal resistance and thus a higher max power in ambient air and without a heatsink.

Here is a great Application Note by Texas Instruments that explain PCB thermal design:

https://www.powerelectronictips.com/heat-sinks-part-1-thermal-principles/

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