Low-battery measures
When your cellphone battery runs low, you have to take take low-battery measures such as reducing brightness, closing applications or maybe even switching on airplane mode.
A: "Why is your screen so dark? Do you even see something?"
B: "I'm running low on battery, I have to take low-battery measures to make it through the day."
B: "I'm running low on battery, I have to take low-battery measures to make it through the day."