Best way to Power Multiple Raspberry Pi 4 Model Bs

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frankv

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#2581496 8-Oct-2020 16:36

Paul1977:

So I assume this one, or similar, would be more than sufficient?

But how do I connect the pis to it? Just connect all four in parallel to the output terminals?

Yes, connect them in parallel... GND & 5V to each RPi. Don't daisy-chain them -- in that case to carry 12A the wires from the PSU to the first RPI would need to be 11AWG (2.3mm diameter conductor!) (https://www.powerstream.com/Wire_Size.htm). For 3A, you only need 1mm dia conductors. At low voltages, shorter wires (within reason) are better.

NB: Cheap USB cables have less than 1mm dia wires

huckster

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#2581550 8-Oct-2020 18:24

Keep us posted on which way you go. I bought an Anker but it doesn't cut it for the newer Pis.

Paul1977

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#2581793 9-Oct-2020 09:56

huckster:

Keep us posted on which way you go. I bought an Anker but it doesn't cut it for the newer Pis.

@huckster I'm almost certainly going to go the passive PoE hats I linked above, but will be a few weeks to get them from China.

I'm fortunate that I already have a switch capable of passive 24V PoE. They're half the price of the official 802.3af hats, and can also output more amps / higher wattage (15W vs 12.5W) - so for me I can't see a downside.

Once I get these I'll let you know how they go.

Paul1977

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#2581851 9-Oct-2020 11:20

Another question:

What are peoples thoughts on cooling requirements for the Pi 4 Model B?

I'm looking at getting a case with multiple layers and open sides so I can stack the Pis, but not sure if I need active cooling? The PoE hats I'm looking at come with a heat sink for the CPU, but has some pins that may prevent a fan being able to be placed above CPU.

They will be in a small 9RU network cabinet in garage that has fans running (but a large switch will prevent the fans blowing directly on the Pis).

PoE Hat and Heatsink

Layered case without fans

Layered case with fans, but suspect pins on PoE hat will be in the way of fans?

richms

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#2581876 9-Oct-2020 12:41

You can always get some longer standoffs to space things out furthur if the fans hit.

I only have single pi's deployed and half of them are just running emulators which dont seem to really stress it enough to even need a heatsink.

Richard rich.ms

Paul1977

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#2581881 9-Oct-2020 12:56

richms:

You can always get some longer standoffs to space things out furthur if the fans hit.

That's a good point, thanks.

HP

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PANiCnz

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#2581973 9-Oct-2020 16:02

Have you seen this case? Would probably provide the best cooling performance.

Paul1977

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#2581978 9-Oct-2020 16:13

PANiCnz:

Have you seen this case? Would probably provide the best cooling performance.

No, hadn't seen that one. Probably quite a good option, but perhaps a little bulky?

A bit late for me as I've ordered this one now anyway, which I'm hoping will do the trick and take up less space if I lay it on it's side. From the same seller I notice.

huckster

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#2653233 10-Feb-2021 19:32

Hey Paul1977.

How's the Pi Powering going?

Are your PoE hats working?

:-)

neb

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#2654631 11-Feb-2021 13:44

frankv:
Yes, connect them in parallel... GND & 5V to each RPi. Don't daisy-chain them -- in that case to carry 12A the wires from the PSU to the first RPI would need to be 11AWG (2.3mm diameter conductor!) (https://www.powerstream.com/Wire_Size.htm). For 3A, you only need 1mm dia conductors.

That always amuses me with 12V power bricks, typically for LED lighting, they'll claim 10 amps with something like 28 AWG cable, so it's actually a hot wire cutter for styrofoam for the first 30 seconds and an open circuit after that.

Mehrts

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#2654799 11-Feb-2021 17:30

Edit: Just saw the date of the original post 🤦‍♂️ Anyways..

I've got a couple of headless RPis (3B+ and 4B) both powered via the "official" PoE hats.

I've removed the tiny fans which these come with, and made a case to house both RPis plus an 80mm 12v fan which I power from the GPIO pins off one of the RPis. This keeps things cool, while also reducing the fan noise. Both RPis have small heat sinks on the appropriate areas.

The beauty of having everything PoE powered, is that I can remotely do a hard reboot by disabling/re-enabling PoE, and also monitor the total power drawn by each RPi via the switch port stats page. I also love only having the ability to power them via one cable each.

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