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About the PoE HAT...with respect to the Pi4B

Posted: Thu Jul 18, 2019 11:41 pm
by W. H. Heydt
According to the box my PoE HAT came in, its output is 2.5A. While that is enough to run a Pi4B, so long as there aren't any really power hungry peripherals, the Pi4B spec is, as we know, 3A. So...Is an upgrade to the PoE HAT to provide the full 3A intended to happen some time?

Re: About the PoE HAT...with respect to the Pi4B

Posted: Thu Jul 18, 2019 11:51 pm
by trejan
Yeah. I've been wondering about this as well.

Is the 3A requirement for the RPi 4 because USB-C only offers 500/900mA, 1.5A and 3A or because it does actually want 500mA more than a 3B/3B+? The PoE HAT is listed as compatible with the RPi 4 but as mentioned in the above post, it only does 2.5A. Can it fully power a RPi 4 with everything installed/connected because the actual maximum curent draw is 2.5A or should we be conservative?

The PoE HAT would have to be upgraded to support 802.3at aka PoE+ if we want 3A out. 802.3af supplies 15.4W but only guarantees 12.95W delivered to the device due to cable losses. 12.95W would be 2.59A at 5V. Trying to draw more will cause most PoE switches to cut power entirely as it'll detect it as an overcurrent fault.

Re: About the PoE HAT...with respect to the Pi4B

Posted: Fri Jul 19, 2019 7:38 am
by jardino
I've been running my Pi4B 2Gb on a PoE HAT for about a week with no problems. I've not heavily stressed the 4B yet, though.
Alan.

Re: About the PoE HAT...with respect to the Pi4B

Posted: Fri Jul 19, 2019 8:15 am
by alphanumeric
For what its worth, I'm running my Pi 4B on the official 2.5A Micro USB supply, with a USB C adapter. With no issues. I haven't plugged much into as of yet though. Monitor keyboard and mouse. The official 3A supply was out of stock when I ordered my 4B. And I didn't want to chance my 4B going out of stock while waiting on the power supply. Will tag along in this thread though to see what info comes down the pipe.