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I'm trying to decide what is the best option for powering a Pi4. The specs mention for a minimum of 3A. Let's consider we would also like to connect a 2.5" drive to the Pi4. Could someone more experienced with power supplies help me with the following?

  • How far can we go with a good 2.4A USB charger?

  • The official power supply is rated 5.1V/3A. Does this mean that this may turn out to be inadequate?

  • Some 3rd party chargers (e.g. the one discussed here) are rated for 3A in Quick Charge mode. Will the QC mode be activated with RPi4? Or the charger will operate as a regular 2.4A charger?

  • How can we tell apart 3rd party chargers that would work with RPi4? Are there any of them? I've seen a couple of models mentioning 5V/4.4A output. But I'm afraid this is only the aggregate amperage (they were multi-port USB chargers).

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  • Well, a 2.5" drive might take 500mA or more. So I think the official 5.1V 3A PSU does not cater for your special needs. These couple of years I have been using 220VAC to 12V DC 5A/10A PSU (Well, those cheapies you can find at eBay or AliExpress). Then I step down 12V (or 11.1V if I am using LiPo power banks) to 5V 3A/5A/10A for my different projects. In case you ask, I NEVER use any of those ugly looking plastic covered wall wart dumb or smart "chargers" for my Arduinos or Rpis!
    – tlfong01
    Jun 26, 2019 at 14:30
  • Just to clarify, the official 3A recommendation for the Pi 4B includes 1.2 Amps allocated to USB peripherals, each of which can draw up to around 500mA. The Pi 4B itself without any USB peripherals will therefore consume less than 1.8 Amps at peak even when ethernet, wifi and bluetooth are all in use and maybe even the headers for camera and display. At idle, it'll be less than 1 Amp. The Pi's charging port is relatively tolerant to under-voltage so powering it with a charger that provides too little current is unlikely to damage the Pi beyond making it unstable at some point.
    – thomasrutter
    Oct 9, 2020 at 2:07

6 Answers 6

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The best option is a good quality power supply, as cheap brands may say they are rated at 2.4 amps, when they don't actually supply that much. Based on the numerous bad experiences i've had with 3rd party chargers, i'd highly recommend buying the official one from the foundation!

Whether that is adequate for the hard drive is another question. I haven't tried the Pi 4 yet, but my 3B actually worked fine (with no low-voltage warning) with a 1A USB hard drive plugged into it. The adapter powering the Pi was rated at 2.1A.

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    Apparently the USB-C port on the Pi 4 is non-spec and many quality "e-marked" chargers will detect the port is wired incorrectly and refuse to charge. Looks like a fix is in the offing though. Source: arstechnica.com/gadgets/2019/07/…:
    – F1Linux
    Jul 9, 2019 at 16:17
  • All answers made meaningful contributions. Because of the non-compliant USB-C implementation, I've accepted this as the right answer. Until a new version of the board comes out, probably the safest bet is to go with the RPi foundation PSU.
    – m000
    Jul 10, 2019 at 17:23
  • @m000: I disagree that buying a charger from "The Organization" is the "safest bet". Any charger that supplies sufficient current within the specified voltage limits will work fine. The only exception is IF you have the "bungled hardware design version of the RPi 4", AND cannot obtain a non E-marked USB-C cable. All other combinations should work fine with any voltage- & current-compliant supply.
    – Seamus
    Jun 20, 2020 at 2:40
  • @Seamus Thank you for the physics lesson, but we have neither specific figures for the total power draw of the described setup, or the per-port amp rating of most 3rd party PSUs. Without specific figures, we're betting. And our best bet when the Q was written was the official PSU, which you can reasonably expect to have been tested in a number of common setups. I would go for a 3rd party RPi4 PSU only if (a) it specifically mentions "RPi 4 compatible", or (b) clearly marks the V/A per port. If you know of any such models, feel free to add an answer for the next users to come here.
    – m000
    Jun 22, 2020 at 16:45
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    Update on comment by @F1Linux: the latest revision of the Pi 4 fixes the USB-C non-spec problem and is available now: tomshardware.com/uk/news/raspberry-pi-4-usb-c-update.
    – Hugh W
    Jun 30, 2020 at 14:02
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Use a PoE Hat:

Third-party USB-C charging devices can be cheaply wired, potentially destroying connected devices as well as starting fires. A safer alternative is to power your Pi using PoE which beyond reducing these risks, offer additional benefits:

Benefits:

Using a PoE Hat is easy to setup and enables you to:

Additional Requirements:

In addition to a PoE Hat, you'll require a PoE switch and some decent Ethernet cables. Some suggestions for which I've had great results with my own PoE Hat use are:

Cost Comparison: Mains vs PoE: Total cost of a PoE Hat + 5 ft Tripp Cat6 24 AWG Ethernet cable = £20, versus £8/each for a "official" (genuine; not third-party) Raspberry Pi USB-C mains power supply unit. But for the £12 difference the additional benefits described above I feel are worth the small premium.

Pi 4 Compatibility: Haven't myself yet been able to get a Pi 4 (vendors I tried were out of stock unsurprisingly) but found this link to a Register article about the Pi 4 which notes the PoE Hat IS compatible in their report on the new Pi

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    I bet one can also start a fire with a crappy PoE hat. If anything, 48V has higher damage potential than 5V.
    – Dmitry Grigoryev
    Jun 28, 2019 at 23:23
  • @DmitryGrigoryev I supplied links to quality Ethernet cables as well as a reputable Vendor & model of a PoE switch. Indeed, I’ve used this combination to power 8 Pi security cameras for over a year now without issue and I sleep like a baby. I also provided links to articles describing blown up gear and fired from cheap third party usb-c cabling. “Crappy” PoE? PoE is widely used in industry and proven.
    – F1Linux
    Jun 28, 2019 at 23:37
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    I don't think you understood me. I didn't say all PoE equipment is bad, but some of it certainly is. The same is also true for USB. You make it sound like USB-C is somehow unsafe, and link to an article I don't find trustworthy as proof. Do you seriously think that the fact that you "sleep like a baby" while using PoE is a valid technical argument? Sure, I readily believe you that your $100 PoE switch is better quality than a $5 USB brick.
    – Dmitry Grigoryev
    Jun 29, 2019 at 13:40
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    Lo and behold: "Halt and catch fire: The perils of cheap PoE'.
    – Dmitry Grigoryev
    Jun 29, 2019 at 16:44
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    Read my original post where I suggest QUALITY 24 AWG Cat 6 Ethernet cables from a reputable vendor. Although you are offering this after the fact, I’ll say that it’s a fair consideration that deserves treatment in such a discussion as this. Maybe the issue is better phrased as “cheap third-party after market electric products” than specifically being exclusive to either usb-c or PoE. Anyway, sounds like we’re mostly on the same sheet of music about risk.
    – F1Linux
    Jun 29, 2019 at 17:03
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The spec specifically states that:

A good quality 2.5A power supply can be used if downstream USB peripherals consume less than 500mA in total.

Using a 2.4A power supply with the Pi 4 and a 2.5" HDD is going to be borderline assuming a typical power rating of the 2.5" drive of about 1.8W to 2.7W (see here). From the above statement - after all it really says that the Pi will need just 2A - the official supply should however work.

According to this answer Quickcharge modes are likely not going to help.

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4

How can we tell apart 3rd party chargers that would work with RPi4?

You can either rely on reviews or ask the seller and take their word for it, or you can get the supply, test it, and return it back if it doesn't perform. Obviously, in the latter case you'll want to buy it from a place where you can return it for free.

There is no way to tell from the labels how much current a power supply can really deliver. I've seen 2.5 A chargers which go down to 4V at nominal current. Good enough to charge a phone, not nearly good enough for a voltage-sensitive device such as an RPi.

One place which (surprisingly) sells very decent cheap 5V PSUs is IKEA. They offer a 3-port charger with 3.4A total current, 2.4A per port, which really holds its promises. If you need lots of power, plugging the RPi in one port and a powered hub in another gives you a combined power of 17W.

If you want to (try to) get away with something cheap, check out this charger. It has enough power to get the RPi4 running, so if you deem a non-certified charger safe enough to use (hint: most of the cheap electronics you buy over the Internet isn't properly certified), go ahead.

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  • The last recommendation from Ali Express is precisely the type of chargers I am very sceptical about: 4A seems to be the maximum aggregate output. If you look in the product photos, it seems that the charger delivers only 2.1A per port on fast charge mode.
    – m000
    Jul 2, 2020 at 18:35
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    @m000 I disassembled one of those supplies, and, not to much surprise, all USB ports are shorted together. There is nothing there to limit the current per port. I have run a Pi 4 for months with one external HDD permanently attached to it and a second one being connected occasionally. With a custom cable capable of 4A, I never had under-voltage. I have since replaced it with a proper 4A power supply though, one that is better build, has proper voltage regulation and doesn't get as hot.
    – Dmitry Grigoryev
    Jul 3, 2020 at 8:56
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    I get low voltage ratings on my pi4 using an Ikea charger and cable.
    – UpTheCreek
    Feb 3, 2021 at 19:22
  • @UpTheCreek Do you have any USB devices connected to the Pi? What is the AWG rating of the cable? I also had to move away to a 4A supply and AWG18 cable because there's an HDD and a bunch of other stuff permanently connected to my Pi4. Still, I had to set my supply to 5.4V, otherwise the HDD would lose power once in a while. At 3A, the Pi barely gets 5V on the GPIO, losing 0.4V in the cable and connectors. The Pi Foundation should really have implemented USB PD in Pi4.
    – Dmitry Grigoryev
    Feb 4, 2021 at 8:25
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Fortunately I gathered much experience over the years. The most important with theese is how they are designed. You should never, i mean NEVER buy shady power supply from unknown chinesse sellers / ebay / aliexpress etc.! Majority of them are really badly designed. They might kill not only the device because of poor design, but also YOU because of poor high and low voltage separation. But the shady sellers don't really care, the job is done when the sale is made. Problems they usually have:

  • Insufficient high and low voltage separation. 220V lines are too very close to 5V on PCB which can cause 220V to get to the 5V line and you are dead.
  • Voltage not 5V which can kill your device. Often, when they are under load voltage starts to drop, or they emit excessive heat.
  • There is a lot of noise on the output. Voltages goes up and down from like 4V to 6V or even more. This can kill your device.

So a general advice would be to buy it from respectable manufacturer like samsungs, htc, lg, apple, and other major brands. According to tests they are generally very good.

As stated in previous comment, IKEA makes very decent USB power supply (tested). Also (you wont belive) their LADDA rechargeable AA and AAA are most likely Panasonic eneloop PRO acording to tests. So IKEA is probably a safe and good choise for power supply.

I would suggest you choose based on information on this web site, where this Danish guy makes reviews of chargers with proper tests and measurements from electrical point of view: https://lygte-info.dk/info/ChargerIndex%20UK.html

Example of good ikea charger: https://lygte-info.dk/review/USBpower%20Ikea%20Lorby%20USB%205V%203.4A%20303.877.07%20UK.html

Example of BAD and dangerous fake apple charger: https://lygte-info.dk/review/USBpower%20New%20European%20standard%205V1A%20plug%20UK.html

Also dont watch the hipsters chargers reviews on youtube, where they comment, color of cable, number of ports, etc. it is useless. You need measurements like this Danish guy does it.

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    That IKEA phone charger isn't good enough to run an RPi3B+, so it's likely not good enough for a RPi4B. I had some long discussions with the Raspberry Pi Foundation on that subject when the 3B+ was new.
    – Dougie
    Sep 1, 2019 at 13:31
  • @Dougie I have a different IKEA charger but with a similar spec: 2.4A from one port, 3.4A total. It runs an RPi4 and an HDD connected via a powered hub just fine. I have good cables though.
    – Dmitry Grigoryev
    Sep 28, 2019 at 5:38
  • @Dougie, I had similar problems with IKEA power-strips that claimed one thing but under delivered on power.
    – Wavesailor
    May 1, 2020 at 18:47
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    My IKEA charger didn't even charge the phone in Japan (with their weird 100V mains).
    – Dougie
    May 2, 2020 at 10:37
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    "Currently i power my RPI4 with this one: aliexpress.com/item/… " It's funny how you stress out one should NEVER buy a shady power supply from aliexpress, state you're using exactly one of such supplies :)
    – Dmitry Grigoryev
    Jul 3, 2020 at 9:09
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I've successfully powered a Pi 3B+ using a cheap 12V 3A wall wart from aliexpress and a cheap buck converter from aliexpress. The 12V 3A provides for well above 3A when dialed down to 5.1V through the buck converter.

The most difficult part is soldering wire on to a USB plug.

https://www.aliexpress.com/item/33014935336.html

https://www.aliexpress.com/item/32798886986.html

I plan on doing the same for my Pi 4 when it arrives.

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    Why not get a 5V wall wart right away? Do you need 12V for something else? Having two voltage regulators in a chain just multiplies the losses and the failure rates by two.
    – Dmitry Grigoryev
    Jul 3, 2020 at 9:02
  • Becasue I find that unless you're paying $25, you can't guarentee that you'll be getting 5V. If your putting 12V into the buck converter, it's pretty good at keeping 5V comming out. In some applications I also happen to be using 12V as well. I find the buck converters to be pretty durable, I havn't had one fail on me yet.
    – bor999
    Jul 30, 2020 at 18:10
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    That's a much worse experience compared to mine. I only got one 5V PSU which was not delivering 5V at full load, and I simply returned it as broken.
    – Dmitry Grigoryev
    Aug 6, 2020 at 12:23

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