5

I would like to run about 4 or 5 Pi's at once and in searching the internet for a multiport power supply, what comes up is chargers.

Does this semantic difference (power supply versus charger) matter very much if the charger is rated with a high enough wattage to support 4 or 5 devices at once?

  • 1
    I am using multiport USB chargers to run my Pi's and it works perfectly. Note that not all chargers offer the higher amp ports that the Pi3 really requires.Another thing to be concerned with is cheap/long USB cables which can negate the higher amperage supply. – Steve Robillard May 12 '16 at 1:12
  • Ok. I was paying attention to the amp/voltage specs. – Ken Ingram May 18 '16 at 19:46
4

Sorry for answering an OLD question that has a good answer, but I have a good solution too. Great for anyone who's not afraid of a little DIY.

I have a stack of Raspberry Pi's here. All of them have more than enough power at all times.

  • 2 x RPi 2B
  • 6 x RPi 3B

Since I wasn't too happy about getting expensive USB cables, and I'm tired of cheap USB cables that under-perform, due to low cable cross-sections, that drops voltages, get hot and stop working, I made my own solution.

Another plus-side to my solution, is that I didn't have to get an 8-port 20A hub (8 x 2.5A) To make sure they have all the power they could possibly need.

The explanation: They are all getting power from a 120w laptop PSU. This PSU delivers a bit more than 10A @ 19.5V regulated DC. This voltage is way too high, so I had to have some fun.

I hooked two cheap DC-DC converters up to the PSU. They take any DC voltage from 24 to 12, and the ones I got, outputs a nice ~5.1v under load.

  • Link (Not this exact module, but similar)

From the outputs on the converters, I used the cheapest 18AWG(0.8mm²) cable I could find. 18 AWG is actually alot thicker than needed.

  • Link (Looks like this. I got one red, and one black spool)

I also got a bunch of micro USB B plugs with solder tabs.

  • Link (Could be these. Not sure)

On the plugs I used, I shorted the D+ to the D- line, since I don't know if the Raspberry checks what power supply it is connected to, and I soldered the 18 AWG cables to the VDC and GND pins. Then I put shrink tubing on the connectors to make it look a bit better.

I tested with dummy loads to see how the dc-dc converters held up.

  • With a 20mA load each, they buth output 5.19V
  • With a 10A load each, one were at 5.09V, and the other 5.1V

I ran the test for 30 minutes to see if voltages and temperatures were stable.

Now, I doubt that they will EVER draw that much power, but at least they have a good supply.

PS: The reason why I didn't power the 5v rails directly, is the protection offered by the polyfuses.

A tip: I put a 10.000mAh portable charger between the PSU and one RPi3 as a simple UPS too.

  • Cool. If one has the time to take this approach it's pretty good. – Ken Ingram Oct 12 '17 at 20:44
  • Yeah. just make sure the converters supply a stable voltage, or add some caps to remove ripple.. – svin83 Oct 17 '17 at 13:01
3

I found a $20 solution -- an Obsidian Series 6-Port 8A USB Smart Charger from Monoprice. 6-Port 8amp USB Smart Charger

  • This charger shouldn't be sufficient for even 4 Pi's v3 running with full capacity. Charger might have potential problems with running multiple Pi's v3 (they need 2,5A 5V - official Power Rec reference). So if @KenIngram needs 4-5 Pi's v3, this won't work for all of them with full capacity. Generally, these chargers support max 2.4A per port, but this value is only the maximum, usually, it oscillates around 1,9-2,2A, so even 4 Pi's v3 might have some problems while working on demanding tasks. – Egel Feb 18 '18 at 1:07
  • The device indicated that it satisfies a requirement for steady 2.5 A, which is why I use it. If I had more demanding tasks, I would scale appropriately. This has been sufficient for standard tasks. – Ken Ingram Apr 3 '18 at 23:09
2

A power supply is anything that provides power. A charger is a power supply whose main purpose is to charge batteries. Since the Pi doesn't have any batteries, what you connect to it is by definition a power supply :)

Now that we got semantics out of the way... the recommended amperage for the B+ and the 2 is 2A, and for the 3 it's 2.5A. While I have never observed my Pis draw more than 1A, in fact, very rarely will they go above 500mA, if you populate all four USB ports with devices that draw power, you might reach those limits. To run 4-5 pis out of a single PSU, you'd need one capable of providing between 5A and 10A, and then you'll have to cannibalize some USB cables to power the things.

Overall, you're not going to gain much in terms of space. I'd stick to five wall warts on a power strip.

  • Thanks for the semantic clarification. That was actually where I was stumped. – Ken Ingram May 18 '16 at 19:49
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    Incidentally, I gained quite a bit in terms of space, so you were very wrong on that count. – Ken Ingram Jan 7 '17 at 12:05
2

I am using a Photive 50W power supply with 6 USB ports to power 3 Raspberry Pi: one B+, one 2 and one 3. This is the Amazon link: http://www.amazon.com/Photive-Desktop-Charger-Intelligent-Technology/dp/B00LMIA9L4/ref=sr_1_16?ie=UTF8&qid=1463030603&sr=8-16&keywords=50w+usb

1

I use a repurposed XT PSU from an old PC which has the added benefit of keeping the Pis cooled with it's fan. Mine is capable of providing 21 amps on the +5v line but they vary, it is normally written on the PSU. Here's a link to various instructables on XT and ATX PSU conversions http://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/

  • Could you give some details on the specs of said PSU? – Darth Vader May 12 '16 at 7:11
  • That's one of the things I was considering. Though I would like a low noise solution. – Ken Ingram May 18 '16 at 19:47

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