Under-voltage problems when using the new PoE hat

Question

I'm experiencing some issues with the new PoE hat when using my NETGEAR gs108pe PoE switch.

Basically when I use my raspberry pi 3B+ with only my HDMI monitor and a USB serial converter attached (NOTE: it gives the same result without anything attached at all), the raspberry pi will randomly reboot once per day or something and the USB devices are switched off and on continuously.

The raspberry pi spits out a bunch of these messages: [ 1193.923325] Under-voltage detected! (0x00050005) [ 1198.083384] Voltage normalised (0x00000000) [56287.274719] Under-voltage detected! (0x00050005) [56288.534031] usb 1-1-port2: over-current change [56288.638020] usb 1-1.1-port2: over-current change [56288.764901] usb 1-1-port3: over-current change [56288.874920] usb 1-1.1-port3: over-current change [56289.004931] usb 1-1-port4: over-current change [56289.114923] usb 1-1.1-port2: over-current change [56289.244915] usb 1-1-port2: over-current change [56289.354923] usb 1-1.1-port3: over-current change [56289.484932] usb 1-1-port3: over-current change [56289.594925] usb 1-1.1-port2: over-current change [56289.724901] usb 1-1-port4: over-current change [56289.835019] usb 1-1.1.3: USB disconnect, device number 4

My PoE switch has a label which states that it can supply a maximum of 15.4 watts per port:

Is it a faulty PoE hat or do I need to configure my switch?

Answer 1

Version 2 of the PoE hat released a few months ago works flawlessly; version 1 had big issues. With the V2 POE Hat, I can even drive an external 1TB USB hard drive directly without a powered USB hub from the USB ports using only the power from the switch. And the Pi will stay up indefinitely until I take it down. To validate that you were sold the newer v2 PoE hat, look for a mezzanine card on the underside as shown in below picture.

If you DO have the V2 PoE hat, check Ethernet cable length in relation to its' AWG size is sufficient to squirt power the longer distance. Thin cables have smaller conductors and are less performant as distances increase from the PoE switch. Understanding AWG Ethernet cable sizing: a LOWER number offers a THICKER conductor with lower resistance. ie an AWG 24 Ethernet cable is THICKER than an AWG 26 one. It's easy to forget about the cable between the PoE switch and the Pi ;-)