Why does my Lenovo Y40-70 Flicker when in use on low battery?

Saving power, skipping cycles to save energy.

Because there are two brightness settings, one for ON BATTERY and one for ON POWER SUPPLY. The BIOS allows them to be different and remembers them for you. So obviously usually that means DIM for on battery and BRIGHT for on power supply. Alternatively its Lenovo doing their best to tell you in a few seconds the unit will go to STANDBY. You might get that situation if your power cord(plug that you push in) or/and your power JACK socket(the hole you push the power cable into) may have been damaged/lose connection/come unsoldered. Also most supplies include a CENTRAL pin wire that tells the BIOS that the power supply is INSERTED this might have a broken wire too. With the power supply unplugged from the pc it should not do that.