I have a pi model 3b. When I power it through usb the onboard Wi-Fi works great. But when I power it through the 5V gpio pins with batteries the Wi-Fi doesn't seem to work at all. I measured the voltage with a multimeter and it is properly getting a steady 5V and drawing about 0.4A.
Is what I'm trying to do even possible or there is some kind of limitation on what can be powered through gpio and the wifi will never work that way? If it is possible, any tips on how can I debug this issue? (I read that power saving mode is turned off by default now so it is probably not related to that. I'm on raspbian totally updated/upgraded).