As appreciated as your tests have been for me, this is the best.
So many of these cheap chargers… I feel like you’re driving a car steering me to the good stuff.
GREAT work HKJ!
Great review, very important safety facts!
Highly appreciated!
Insipred by this thread, I tore down one (failed) Xtar WP2 II power supply unit.
Since I’m no-pr0, I will post pics to another thread and let You guys decide “what it has eaten” :bigsmile:
Here is a link to tear down: Tear Down: Xtar WP2 II -power supply unit
Awesome review, thanks HKJ!
If you look at the myriad of PCBs out there in electronic devices the distances separating circuitry apart from disaster is likewise as these USB units. The point being is don’t get these type of things wet or for that matter any other similar device, nor mess around in there unless you know what you’re doing and you should be fine. Even if gaps somehow connected with the AC voltages involved the result would most likely be a fried connection, a strong smell, and a device that doesn’t work.
The tests here IMO would have more credence if the author subsequently bridged these gaps, submerged the units, or some similar test to see what actually happens if said gap was bridged. Think UL Labs testing.
IOW, overeaction IMO.
The safety standards says 4 mm distance in air, on a pcb it will be longer, except if it has a special isolating coating. This distance has two purposes, one is to withstand humidity and dirt, the other is to withstand transients on the mains.
I did not open the transformer, but it will probably also fail the safety standards on the cheap units.
Read this article from BBS, especially the bottom part, that is what can happen with the worst of these chargers.
What’s the gap safety spec if they did have it?
A UL Labs style torture test would be interesting. Do they catch on fire, go into electrocution mode, etc. IMO, any electrical device that’s abused whether by liquid, cord yanking, what have you, is potentially dangerous. The construction of the units claimed as being unsafe on the surface seems pretty robust. I don’t see dangling bare wires or particularly shoddy soldering IOW.
The safety standard is called IEC60950-1 and is implemented in many countries (including US). One important aspect of it is that any vital to safety isolation must be double thickness or two layers normal isolation. There is also different requirements in US and EU, because the mains voltage is different (110VAC vs. 230VAC).
For US indoor equipment with safety earth only needs 1 mm safety distance, without earth 2mm, in "Polluted degree 3" environment it is 2.6 mm and all these distances can be reduced if the factory does a high voltage test on equipment, before shipping.
The standard does list many other safety requirements, including detailed specifications on how solid the equipment must be.
IOW not three pronged like you typically see on most power tools? If they had it then the 1mm distance would be ok? I was also thinking about US and EU voltages and their respective different safety guidelines as you wrote the reply.
I think if we dissected most Chinese inexpensive electronic devices a good many of them would also fail under stringent wide safety criteria as well. 
As air distance yes, not on a pcb.
Because both EU and US uses the same safety standard, the differences are probably minor, and all equipment that can work on bot 110 and 230VAC, needs to use the larger distances.
I do believe that.
Thanks! Glad it was tested and found to be different from the Apple chargers. Hard to tell these days who builds what for whom and to what standards
I believe that big brand names are careful with the security, just imagine what it would do to Samsung or Apple if one of their charges killed a child!
Thanks for the reviews HKJ.
wondering about my computer’s USB ports now.
Excellent work, thank you.
Any plans to do car chargers/power supplies ?
:hopeful smiley:
Not at the current time.
great info. Thanks HKJ.
eek I’ve just ordered one of those uk ones in that review from fasttech, think I might remove it from the order while I still can
Thank you, HKJ, for such a comprehensive review.
I was thinking of buying what looks like the same 4 USB power adapter on Ebay, but with the name YOOPOO (!). So it is nice to see it covered here. I wonder if it is the same adapter but with a different name?
After HKJ reviewed the Ioncell USB charger from IO I bought the car adapter from the same manufacturer:
http://intl-outdoor.com/ioncell-dual-usb-car-charger-p-335.html
The one I received is white though.
I managed to take it apart without much damage, only some scratches. But here are the internals, maybe someone can tell us something about them:
The LM2596 is a acceptable switching regulator that can deliver 3A output, if everything around it is done the correct way.
It does look like the above adapter is a bit low on cooling, i.e. I do not expect that you can draw 3A for long.
To really get an idea of performance, a test is the best way.