Hi ginochip and welcome to the forum!
I tested my 2014 version earlier this week and it started blinking at 3.04V. I'm not sure if it actual protection to cut the current. I was using protected battery and after the light started blinking I tested it with Predator and the protection circuit cut the current. You can notice the decrease in voltage when the three highest modes all seem equally bright and that should be time to change the battery.
I can repeat the test with my 2016 version if you're interested, but it may take some time.