It was switching itself off last night, so I took this reading between switch-offs:
It's close to the '0%' reading which is 114. I'm curious, why doesn't it do a subtraction so that empty is vcc=0, and maybe a further calculation to make it percent? This Forth code would work, assuming the 'vcc' word returns the battery level:
114 vcc - 100 18 */
'18' is there because the scale is 96 to 114, 18 steps. (EDITED to fix the code.)
There is a flash from the LED, I was wrong about that, but of course I have to be looking directly at the Twiddler. In any case, it's very brief and it's green, not red.
I wonder if I'm asking too much of low-battery indication. I think I am, because unless it comes up on the computer screen I'm not going to see it.