The EV3 programmable brick should be powered with 6 1.5 V AA batteries for a total voltage of 9 V.
When total voltage drops below 5 V, you will get strange issues such as the programmable brick spontaneously shutting down.
Connecting to Wi-Fi can quickly drop the voltage.
If you use ev3dev, you can make it easier to learn when the EV3 is dipping below 5 V. The following is an example using ev3dev with Python.
In a shell or script, use
PowerSupply() to access the power_supply class:
ps = PowerSupply()
Then get the battery's voltage at the time of measuring through:
Now you can have the EV3 give you a warning if the voltage drops below a threshold you specify. For example:
if ps.measured_volts < 5:
ALL_LEDS = [Leds.LEFT, Leds.RIGHT]
for l in ALL_LEDS:
Sound.play("Feed me. Feed me. Feed me.")
Read more about the available methods in the ev3dev documentation.