While I was driving my Vex Spin-Up Competition robot I went to replace the battery with one that finished several minutes ago, I took the battery of the charger but as soon as I plugged it into my robot and Pressed the Power Button on my Brain I received the Critically Low Battery Error, but here’s the thing if I press the button on the battery to see battery life it shows Four Solid Green Leds along with the Fast Flashing Red Led. I should go ahead and mention Two of our Batteries are doing this, I currently don’t know If we have any other batteries doing this but I will keep an eye out for them. So what does this Battery Error Mean?
this may help you
run the battery medic (make sure VEXcode is closed), perhaps one cell is failing.