What do the Ninja Blast light colors actually mean while charging?

blink to charging confused me when I first got the device. I thought it was an error so I unplugged so waited around 20 minutes before I remembered how it works.
 
Ninja could have easily added an extra paragraph in the quick start manual stating the blinking indicators for the device. Blink red = critical battery level, blink yellow = low battery level, blink green = charging, solid green = device ready to use. Four lines. Instead they bury it on page 11 of the manual.
 
genuine question, has anyone tried to charge it off a power bank? worried about the low output from the power banks maybe it never gets to solid green.