Raspberry PI cluster - what's the best power source?

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Currently I have my openHAB running on an RPi4, and as I’m using some legacy 1.x bindings, I have to use another one for those in parallel.
I also have some Pis running for other purposes (multiroom audio, etc.), so I was wondering if there is some decent enough powersource to power all those devices? I searched up and down, and I came only across some 2.4A USB hubs or power cables - but noone offers more than one 3A+ USB-Port for loading…

Am I just blind? or do I have to use a bunch of single-3A power sources (which should have significant lower efficiency as one “big” one?), I imagine?

Someone out there also using a cluster of Pis with a good power solution for that?

IMO this is a question for a Raspberry Pi forum where the Pi experts post.

You could get a PC power supply, they usually have 10-12 phases incl. some 5V.

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Along a similar vein as the above: just a normal embedded switch mode power supply would also work. As an example:

I’m considering something like this, for very similar reasons to you. I’d prefer not to have to use a separate power supply for each Pi. Of course, this means if the one supply fails for whatever reason, all the Pi’s go down, but for my use case this is fine…

I use this for my stack of Pi’s with mains power supplied by a UPS. Its been running fine since 2018 with 4 to 6 Pi’s

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Thanks for all the suggestions, the newest Pis since 4 need stable 5V (best 5.1V) and - that’s the more important part - more then 2,5A. And that’s where in my experience all the power supplies lack stable Amperes… most do have 2.4A for their ports, which is not enough for Pi4s…

But yeah, I already took a peak into Raspberry forums - and they don’t seem to have this issue I have…

Surely it’s just the case that a Pi4 can draw over 2.5A when it’s doing something super-duper intensive (and if there are hungry USB devices or other interface peripherals plugged in), but otherwise it will be way less? See these articles, for example (though they don’t show instantaneous, which might be important):

In any case, that’s why I recommended an embedded power supply - no limit on draw up to the supply’s rating, but that’s also because it doesn’t have individual (or any) USB ports - you’ll have to use or make up your own cables.

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I use one of these: https://www.kjell.com/se/produkter/el-verktyg/stromforsorjning/nataggregat/mean-well-switchat-nataggregat-5-v-dc-50-w-p44814
to power my pirack and that seems to work fine. Connected the power directly on the GPIO pins so I didn’t have to work with different USB connectors since I have both pi3 and 4’s in the rack.

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I power all mine from POE with the switch on a big UPS. Does mean you have to buy the POE adapters.

Ira

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I’m also running my Pi Rack with a: https://www.amazon.de/dp/B01JFO9T9E
@John_Galt what kind of cables are you using to the io pins? IO cables seem really thin, but maybe it works anyway given that it is only at 5v.

I have a power supply similar to yours. However, I have soldered a number of USB-A connectors of a perf board and connected both USB-C and micro USB to these. This gives me ~5.09 V and the protection that the USB circuitry on the Pi provides against power spikes. You can but the USB type A connector for cheap at both Kjell and Amazon.

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@seaside I started with dupont wires but then I got a problem with power warnings so I bought 0.5mm2 cables and soldered directly to pins 2 and 6. Worth to note is that I am using a homeprinted box where I have placed a female dc-connector, https://www.kjell.com/se/produkter/el-verktyg/stromforsorjning/natadaptrar/dc-kontakter/dc-kontakt-for-chassimontage-hona-p37331, next to the USB ports so there is no strain on the cables .

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I struggled finding something myself and this was the closest thing I could find:

https://www.amazon.com/gp/product/B076V9PMSM/

my requirements were that able to provide over 2.4A on all ports as most phone charger devices only promise amperage on 1 port.

so far i’ve run it with 2 rpi4’s and it seemed ok. you’ll need a separate power supply though and i think i ended up using a 12V 3A or possibly a 24V ??A from an old laptop. i ended up hiding it in a box that’s a little hard to reach as i run OH from and it and i wont want anybody messing with it.

the downside is that its “open” and kinda a little more of a novelty item and it has crazy bright led lights between the last cap and usb-out port. not good for my “discrete” install.

on another note, i was looking for something like this but with 5 ports b/c my ultimate goal was to also power a 5 port ethernet switch (typically 5v, just rig up the cable) and 4 rpi’s

I have one of these: https://eu.dlink.com/uk/en/products/dgs-105-5-port-gigabit-ethernet-switch installed in my pi-rack that is powered from my PSU as well since it only requires 5V.

That’s nice, I need managed switches though, I experimented with https://www.amazon.com/GAF-5v10w-802-3af-PoE-Splitter-Output/dp/B0167JHY3I Since I have a beefy POE switch next to the cluster, but they weren’t good enough I would say. The PoE hats are a bit too expensive IMO.

This is a managed alternative: https://www.dlink.com/en/products/dgs-1100-05-5-port-gigabit-smart-managed-switch

@seaside thanks for the tip on the switch, nice to know there is one even though I stopped splitting my network since most consumer electronics can’t handle it well, on the other hand, if I get really in to K3S i might like to hide the nodes…

To summarize my thoughts regarding the original question, I think that any external 5V PSU will work better than any USB hub or similar, and with a 5V switch the only problem I have found so far is that I have a 120mm fan cooling my whole setup that needs 12V, but has solved that one with a DC booster.

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Thing is, with many devices drawing >2A power or more, the voltage drops.
Just tested with a 60W, 5port USB device (https://www.quntis.com/products/5-port-60w-usb-power-delivery-wall-charger).
I put a raspberry4 on the USB3-port (18W aka >3A) and put three more Pis on the USB2-ports (12W aka 2,4A) - the pi4 lasted for about 30mins, then the voltage dropped and I got this:

Under-voltage has occurred since last reboot.
ARM frequency capped has occurred since last reboot.

so, my pi4 isn’t worth a dime anymore, if crippled…

I can’t be the only one wanting to use Pis - or charge more than one >2,4A smartphone?

I suspect this speaks to the quality of the power supply more than anything else: constant voltage output over the full rated power range of the power supply should be expected from a good quality supply. As mentioned a few times in this thread by me, @John_Galt and @bdollerup, a real power supply does work, with the disadvantage of not having actual USB ports.

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I had similar challenges with my 7 node pi cluster using “normal” chargers. Even though their nominal power output was rated at 5v, I rarely got more than 4,8 - 4.9 (I measured it). Finally, I had enough and after some YouTube research, I decided to build my own power supply using a 5v power supply and type A USB breakout boards.

I used the following part from Amazon (UK):

@John_Galt I would’ve bought the above from Kjell’s, but they don’t ship to Denmark :wink:

There’s a fair amount of soldering involved, but the header boards make it easier. I ended up creating two “groups” of 5 USB ports each and wired them to the respective outputs on the power supply. The nice thing about this setup is that I can “dial” in the voltage. I set it to 5,09. Now I have all of my Pi working perfectly and I never see an “under voltage” warning.

Feel free to reach out for more details.

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I tried a bunch of them, mostly “brand names” from Anker, Ansmann to TP-Link and RAVPower…
There’s not much left for power supplies!

My 5cent are on the fact, they all do well in charging phones and tablets (even if it is a bit slower and even if the phone tells you, that it’ll load slower as usual) - and are A-OK with voltage dropage, because it’s just 10cent more expensive to invest in solid electronic…