Powering AStar 32U4 Mini ULV with 3V Lithium Battery CR2032

I just got my A-Star 32U4 Mini ULV’s yesterday. When powering with usb, the blink example ran without any issues. But when I tried to power it with a 3V lithium battery thru BAT +/- pins, the LED blinked very rapidly, though a little dimmed, for ~2 seconds then it went dark (only BAT +/- pins were connected for this test). I thought the battery was probably old so I tried again with 2 brand new CR2032s but the same problem persisted. Then I switched to a 3.7V CR123 battery and the blink example worked again.

I measured >2.8V on all three CR2032 batteries so they should work per specs. Both my boards exhibited the same issue so I think it’s unlikely that both were defective. I haven’t measured how much current it draws from the battery. I will check that next.

Has anyone successfully power the ULV with a CR2032?

You are expecting far too much from those tiny cells, using that processor board. According to the documentation provided by Pololu, the Astar mini draws 30-40 mA at 5V, so the current draw from a 2.8 V source will be about double that taking the efficiency of the step-up regulator into account.

The conventional wisdom for CR2032 cells is that you should never draw more than about 15 mA, but many cells cannot even supply that much current for very long. See this technical note: ti.com/lit/wp/swra349/swra349.pdf

You can run an ATmegaxx8 for a long time from a CR2032 cell, but with an entirely different approach. This page covers all the tricks for the ATmegaxx8 processors, and most should work for the 32U4 as well: gammon.com.au/forum/?id=11497

Thanks for the info. I measured ~95mA @ 3.0V running the blink sketch so the CR2032 is out.