Test/review of Rasberry Pi 2.5A (Stontronics DSA-13PFC-05)

Rasberry Pi 2.5A (Stontronics DSA-13PFC-05)







Official specifications:

  • USB POWER SUPPLY, 5V 2.5A

  • Input Voltage VAC: 90-264V

  • Plug Type: UK / Euro

  • Micro USB cable 1.5mtr

  • ErP Level 5 Efficiency Rating





I got it in a white card board box.



It contained the charger and two different mains plugs.









Measurements
  • Power consumption when idle is 0.03 watt

  • usb power is not coded?

  • Weight: 118g including EU plug.

  • Size: 78 x 73 x 45mm

  • Cable is 145cm long with micro usb connector




The charger can deliver about 3.4A at 230VAC. The output voltage starts fairly high and will drop with load current, that is no surprise, the cable is the reason for much of the drop.



At 120VAC the current is slightly less.



For this curve I measured the voltage inside the charger at the output terminals and as can be seen the voltage is very stable.



No problems running one hour at 2.5A.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.



M1: 50,5°C, HS1: 58,9°C
HS1 is the rectifier diode and the area with M1 is the transformer.



HS1: 47,5°C



M1: 43,2°C, M2: 38,8°C, HS1: 44,6°C



HS1: 60,8°C
HS1 is the rectifier diode.



M1: 41,3°C, HS1: 50,3°C
HS1 is the rectifier diode.



At 0.5A the noise is mV 15rms and 122mVpp.



At 1A the noise is mV 24rms and 110mVpp.



At 2.5A the noise is 64mV rms and 120mVpp, all noise values are very low.



Tear down



With help from my vice and a screwdriver I could break it open, but it was difficult.



At the mains input is a fuse (F1: T2A), a common mode coil and the switcher IC (Q1:GR9230HK). Beside the transformer is a safety capacitor and on the other side a opto coupler.
On the low volt side is a rectifier diode and a common mode coil.



From this side the rectifier diode, the safety capacitors and the mains common mode coil can be seen.



The first picture shows the output common mode coil and the rectifier diode on a small heatsink.
On the second picture is the mains common mode coil and the fuse (Wrapped in shrink wrap).



The fuse and the opto coupler is here, there is a slot in the circuit board under the opto coupler to improve isolation.



On this this is the bridge rectifier (BD1) and the reference (U4)





Safety distance looks good.

Testing with 2830 volt and 4242 volt between mains and low volt side, did not show any safety problems.



Conclusion

This charger is not designed to charge phones or tablets and are missing the coding, but it works fine for instead it is designed to drive small usb powered computers. Depending on the computer and attached stuff it may mean 24/7 at high load. Running close to maximum load will cost lifetime on this power supply, there is a capacitor very close to the hot rectifier diode.

It is a good and safe power supply for the intended purpose, but it is not a fast charger for phones and tablet.



Notes

The charger was supplied by a reader for review.

Index of all tested USB power supplies/chargers
Read more about how I test USB power supplies/charger
How does a usb charger work?

Looks good. Really clean output. If this were sold really cheap, tinkerers like me can fix the weak cable easily.

Speaking of replacing caps, I've desoldered a good set from an old motherboard and it's been a wiggling wrestling challenge with those tight packed components, skinny leads and the heat-sinking ground planes. They've got slightly hot to the touch, I do wonder if this heating can have any sort of significative damaging impact on the caps (?). Of course, I plan on reusing them.

I would not call the cable weak, but all cables have resistance. My measurements are done after a usb connector, that also has some resistance.

Heat damage on electrolytic caps requires time. A typical rating for a capacitor may say 105°C for 2000 hours.

Know what? When I first checked this on your website I thought it was a review of actual RaspBerry Pi hardware LoL.

BTW, have this on my wishlist since a long while. Price is shockingly low: Raspberry US/EU AC Charger 5V/3A 3000mA Micro USB Tablet Pc Power Adapter Supply @ prizeshop

Soldered & assembled lots of micro-USB connectors last year for DIY projects and cable repairs, thus I can change the micro plug end and set it with DCP coding swiftly but the question is, how good is that bold claims psu?

It would not have been placed in the usb power category.

A cheap no-name power supply, my confidence will be very low with that, but I have put in a order for it.

very useful post and information, thank you all for sharing!

What’s the charge rate when charging a big phone which usually accepts 5V2A?

What’s the fastest you could observe for phone/tablet charging with this product?

According to his review (above) the charger has no coding. I’m not very knowledgeable about phone chargers, but I’d think that means the phone won’t recognize it as a legitimate charger at all. IIRC, the phone and charger must negotiate for the fastest/highest rate that both of them can sustain. Or actually, the charger is coded for what it can do and the phone selects from the possibilities presented by the coding. So, it’s not really negotiation, but basically works that way.

Thanks for theorizing, but I prefer practical numbers measured

Not so fast, stranger… ;-)

Per USB 2.0 specifications, upon connection the device should start drawing 0.1A (low power) while enumerating/negotiating power, usually a very brief phase. However, if this fails (floating lines: no ID), phones/tablets (at least Android ones, in my experience) default to high power: 0.5A. This may take a few seconds.

I have a DIY USB power supply whose coding I can change with a switch: Apple 2.4A or none.

Per the usb spec, any dumb device can draw up to 500mA without challenge. Fans, LED lights, any low-power junk that plugs into a usb port, all take advantage of this. It’s only with coding that a device negotiates a higher current rate. Oh, this is for usb-compliant devices, on both ends. Not all devices are usb-compliant.

I’ve got a “lipstick” power-bank that will dump as much current as it can manage when my similarly dumb tablet tries to pull as much as possible as fast as possible. The connectors actually get hot from several minutes of undisturbed use. The PB used to work fine, but I think something went mental with it so that it just opens the floodgates. Fine by me. :smiley:

The same tablet will charge — slooooowly — with a cheap 500mA phone charger. So it takes what it can get, whether as much as it can manage, or just a trickle.

For a power supply (vs charger), you don’t want to have coding, because then something smart (in the RPi) would have to suckle a bit to negotiate a higher rate, and then have the PS go full-tilt. Nope, it’s dumb, by design, and will supply full power at the slightest provocation.

Ah, this…

Yep, forgot about the 100mA phase. I sit corrected.

Those @#$% Pi computers don't care a fLick about the power supply coding (actually tested because of reasons). ;-)

Pi computers' power supply units are usually inexpensive versus equally rated phone/tablet chargers.

As some people wrote above 0.5A is a typical value, but some phones/tablets may also refuse to charge.

Nice review… thanks!