Convoy S21B Active Cooling Project

This project came about after my S11 Active Cooling Project. The S11 and associated heat sinks seemed a bit bulky so I looked for smaller heat sinks which would fit something like a Sofirn IF23 or a Convoy S21B LHP531. Then I found searching for 1/16 or 1/18 scale 380 sized engine heat sinks found the perfect size.

On amazon it was the 

32000RPM HighSpeed RC Motor Cooling Fan Heat Sink with Aluminum Alloy


This had a perfect 25mm inner diameter on the heat sink. With the s21B being 27.2mm the heat sink snapped on perfectly only stretching a mere 2.2mm to get a nice tight grip.
I thought it needed thermal tape anyhow so I added it as well.

AI AIKENUO Thermal Tape

The adding the following to power the fan:
Now I have this:

With this battery and fan combo the test showed no step down over the full 2 hour run time.

I was dissatisfied with the volume of the 32,000 rpm fan. 


I swapped them out for :

Liter energy battery 3.7V Lipo Battery 120mAh

This made it look much more compact:

I was satisfied with the cosmetics, saving a properly 3-D printed enclosure. The runtime test failed for the fan and battery combo. At 32000 rpms the fan stopped running at just over an hour. With a rough calculation of the 2x350 mAh lasting the full 2hr test, and the 2x150 mAh failing at half of that. I have 2 choices in my mind:
  1. Swap out the batts for something slightly larger and at 350 mAh
  2. Replace the fan with a quieter one under approximately 10,000 rpm like the fans in my S11 test
I chose option 1.
After rebuilding the charging board and battery layout I ran another test. The upgraded batts lasted until the flashlight started blinking. The the lux measurements only showed about a 10% drop up till just before the power warning blink started.




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