Boost converter single cell AA battery not delivering enough voltage when connected to Wemos D1 mini
What voltage is the battery when operating?
It will also be good to look at the battery voltage with a scope because the voltage may drop significantly when the switch in the converter is conducting but rise during the rest of the cycle. I find that it is essential to use a very low ESR capacitor at the input of the converter - a conventional small electrolytic is probably not adequate, try a tantalum or polymer electrolytic.
Make sure that the leads from the battery are heavy enough gauge, you can easily drop a 100mV or more across the leads.
Another source of voltage drop is the battery holder - the common ones for AA cells use steel springs on the negative end with a fairly high resistance - in one case I had a significant reduction in voltage drop by putting a short length of copper wire across the spring.
Also it can be very difficult to measure the input current at low voltages because the meter itself may drop 200-300mV which together with the voltage drop the cell will experience under load may drop the voltage below the 900mV limit and stop the device working.