This is a placeholder topic for “4-way Fast Charge Buck Module (Compatible with Raspberry Pi 4B & Jetson Nano)” comments.
This 4 USB buck fast-charging module integrates the common 5V charging recognition function, which is compatible with 99% of the mobile phones on the market. Compared … read more
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Hello Core Electronics team,
I want to power 4 x RPi 4B.
Re DFRobot 4-way fast charge buck module, can all 4 x USB-connected devices draw 3A simultaneously?
What’s the dimensions of the Power Input barrel jack required? Is it centre-positive?
Thank you! 
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Hi Veronique,
Welcome to the forum 
The information we received from the manufacturer of this module didn’t have the barrel jack dimensions or polarity listed so I’ve inspected one of the modules off the shelf here.
The barrel jack has an inner diameter of 2.1mm and looking at the board layout it is center-positive polarity. I’ll have the product page updated shortly to include the extra specs.
It’s implied that all four outputs should work independently so I’ve done a bit of internet sleuthing and circuit inspection to try and confirm for you.
The short answer is yes, but you may not be able to power 4 Pi 4Bs.
The fast charge buck module will default to outputting 5V@2A unless a request for more power is negotiated using a supported fast-charging protocol. As far as I know, the Pi 4B does not support any fast charging protocol on its power input so it will just appear as an electrical load and be unable to negotiate for more current at 5.1V (The Pi technically requires a 5.1V supply).
As a bit of an aside I’ve looked into the design of the buck module itself. The module is made up of 4 copies of the same circuit with a reverse polarity protection diode and the barrel jack.
The manufacturer has labeled the IC with: MH KC24 which it turns out is not actually the type of IC but refers to the buck module circuit layout and it likely uses an IP6505 IC.
These two blogs go into analysing the design of the module more thoroughly and testing its performance if your interested.
https://www.electroschematics.com/quick-charge-primer/
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Hi Trent
I think the operative word here is “implied” I agree, that seems to be the case. But have a think about it. At 24W each that is a total of 96W input plus allowance for efficiency. Say 15% which equates to about 110W at least. Noe the device says minimum voltage is 6V or @ 110W about 18.5A. Doubt that input connector would last long at that level and when you are looking at supplies you are getting up into the MeanWell style of open frame units.
Considering above I would tend to rethink the wording provided by the supplier and consider the 24W being the TOTAL capability of the unit.
I haven’t looked into this device in detail as I have no need to (I will not be using one I don’t think) but you are quite correct if it is designed to be a phone charger it will only supply low current unless requested otherwise.
I agree but I think I would change the “may” to “will”.
Cheers Bob
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Hi Bob,
Just to satisfy my own curiosity I have quickly connected a single Raspberry Pi 4B with this power supply and it did power up to the desktop successfully but that is far from a comprehensive test.
We always recommend people start with the official Raspberry Pi power supply for their model of Pi as it is guaranteed to work with a known configuration of software load and hardware peripherals connected.
Because the Pi’s power requirements will vary significantly under different CPU loads and with different accessories each user should always make a common-sense check about what they are asking of a device.
To extend upon your earlier comment, if we assume the module is 85% efficient and running at full power on all 4 outputs then the waste heat generated in the module will be enough to burn anyone who touches the device.
Ultimately the chipsets used in this module are intended to be used for charging battery devices, not providing a stable power supply to a computer.
Plugging 4 smartphones into this device is a different kind of load demand to 4 single-board computers. Smartphones don’t care so much about load regulation voltage accuracy or EMF noise on power rails but it can cause all sorts of issues with single-board computers.
Additionally, smartphones only need full power for a short period at the start of the charging cycle then drop off to just a small trickle charge as the battery nears full charge.
If you are looking for a device designed to run 4 Raspberry Pis then expect to pay a bit more as this module is less than the price of a single official power supply, it would be too good to be true to expect it to work as well as 4 official power supplies at that price point.
The official power supply on the other hand is a dedicated power supply, not a charger, so it has all the load regulation and EMF noise compliance specs you would expect from a fully-fledged power supply.
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Hi Trent
Thoroughly agree with all that.
What I was getting at is a lot of these suppliers leave their descriptive text in a very foggy shade of grey. I haven’t got it up in front of me at the moment but I think this one says that each output is good for 5V @ 3A. It only hints that you can do this with all 4 at once, it doesn’t say you can. But just as importantly it doesn’t say you can’t. It does not say anything about what the TOTAL power is at any one time. To me that is an important omission. Some enthusiastic person is going to buy one of these and try to get 3A out of all the outputs and go away scratching his (her) head wondering why nothing works and wondering what that expensive smell is.
Once again the difference between a charger and power supply has come up. You have pretty much nailed it in your reply. This device would be fine for charging multiple phones but I think that’s where it stops.
Cheers Bob
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FYI, I have translated the IP6505 datasheet linked by @Trent5487676 above.
Yingjixin Injoinic Technology MH KC24 IP6505 Datasheet - English.pdf (723.9 KB)
Original:
Injoinic Technology MH KC24 IP6505 Datasheet - Chinese.pdf (751.6 KB)
The USB charge IC is rated at 24W max (12V @ 2A). It’s quite unrealistic to expect that from all 4 combined, as the power input will definitely be a bottle neck, even at relatively high input voltage. You might be able to get much closer using the solder points on the board than if you were using the barrel jack.
The conversion efficiency is a claimed 95% @ 5V and 1A output, and a claimed 120mV p-p which is about normal for a Pi 4 without many accessories, so you might get away with running 4 Pis but tbh it’s not a great idea.
In any case, agree with all that’s been said above.
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Super, thanks very much for checking on the specs Trent.
I wasn’t aware of the power rail noise and “charger” vs “power supply” issues so this helped a lot
It sounds like I’ll need to look for a different way of consolidating power delivery to my Pi cluster.
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I may as well get enthusiastic and try it, for the price there’s not much to lose (unless I end up frying all of the Pis!)
Thanks Bob!
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Thanks Oliver, so it sounds like I wouldn’t be able to power 2 x RPi 4B at full load in any case…
Back to drawing board
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Hi Veronique
Lucky to power 1 if it has any peripherals hanging off it. Like it has been said it is probably a pretty good phone charger. (that is what it appears to have been designed for).
Personally I tend to go UP when it comes to current capability. Like the first stage of my permanent XMAS lighting. Needed 3+Amps. settled for a 5V 14A power supply. Room for a bit of expansion BUT I am probably not going to have any problems of the not enough current nature.
Cheers Bob
4 Likes
Hey All,
I did a quick test with one of these.
3 Pi’s running VNC:unloaded (2 Pi 4’s and a Pi 3)
All of the Pi’s running Stressberry
The 4 channel fast charge module was being powered by a 12V 5A PSU exclusively through the barrel jack. Fully loaded though I think the voltage drop would be too much. Next order I’ll grab a terminal block adapter and see how much current is being pulled into the fast charge module.
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