I want to try one of those SST-50, P7 or the MCE drop in from Solarforce, sadly their voltage is 3-6 volts, which requires two cr123 primaries. I dont want to spend on primaries and was wondering what is the effect if I run these on a SINGLE 3.7 volts batteries, I know runtime would be reduced but would brightness be affected too ?

Which of these does not have the donut hole ?