What are the conditions which cause the lightning bolt to show up on the Raspberry PI HDMI display, upper right? Does it do this during normal operation? Does it do it while booting with text scrolling on the display?
I have a dozen field deployed systems built out of a 12v to USB switcher supply providing 4.95 to 5.1 volts and successfully running Raspberry PI B+, 2 B and 3 B boards. Some of these show an intermittent color square in the upper right at some points during booting but all seem to run ok. Some of them have been up 24/7 for years. All are presently running Raspbian 8-jessie. Does the intermittent color square do the same thing the lightning bolt does?
Should I be worried about using Raspberry PI 3 running Raspbian 9-stretch with those power sources? I need to run the systems from battery power some of the time and all of the sites have gel-cel and 13.8v AC-DC power supplies so using conversion from 12v to USB voltage is reasonable.
Can you recommend a power supply for the Raspberry PI that draws power from 12V DC?