Inductor Sizing for Boost Convertor - Part 3

As mentioned in this post I used a 22k resistor to program the boost convertor current. However, it made no difference to the results. A large number of the tested inductors lie withing the recommended range of  4.7-22uH yet refuse to work.

I set the output voltage a little higher and repeated the measurements. Destroyed yet another MT3608L in the process. They are not very robust.

When I sat down to look closely at the data it revealed that:

1. Efficiency is highly dependent on battery voltage
   
   

   

   Curious that 22uH wirewound inductors are atypical
   

   
   

2. I didn't test at voltages typical of a LiFePO4 battery, and
   

3. It was unlikely I had the step change in efficiency I was after.
   
   
   

   
    
   

Conclusions

• If anything, I have gone backwards. 
• The atypical 22uH inductor size results could be a clue that I need to be able to get smaller inductors to work with this part to get the efficiency I am after. 
• I am presently stumped why inductors smaller than 22uH don't work.
• Need to re-test with 3.2-3.3 volts at the PCB.