Did any one tried to replace the cooling fans for the battery with aftermarket or using 200 mm pc cooling fans instead?

 

The stock fans are extremely robust and move a LOT of air. A 200mm fan moves less air and would present a mounting challenge.

If you want to ensure your pack is sufficiently cool, make sure you maintain your A/C system, establish cooling patters such that the entire vehicle is cooled down (don't aim all vents at the driver's face) and keep the three battery fan inlets and rear seat floorboard area clear of obstructions.

RX4XXh and Highlander battery cooling systems have proven to be more than sufficient even in hot environments like Phoenix.