Testing USB Outlets in wall socket

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How do I test these to see if they can still deliver their rated 2 amp. They're sort of working but just seem to be taking forever the charge things.

I could connect it up to an amp meter but what could I use as a load to see if it achieved 2 amps. (I take it they are limited to never deliver more than 2 amps?)
 
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They're sort of working but just seem to be taking forever the charge things.

The charging circuitry in some "things" will detect that the USB source is not approved for charging the "thing" and refuse to charge the battery.

Some USB sources in wall sockets are un-safe to connect to electronic equipment due to the output voltage and waveform being far from smooth regulated DC power
 
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Some of my gadgets have a battery-monitoring mini-app built in that graphically shows % charge over time, and estimates "time to full, at current rate of charge"

I suppose if you know the mAh rating of the battery you could watch the time to go from 0% to 100%

You would have to put it in aircraft mode and shut down or sleep apps, with display off, to minimise load during charge.

My Samsung Smart Chargers, used with a Samsung gadget, maximise the charge rate. If I plug the tab into a non-smart charger, the tab complains that it is on slow charge. When plugged into a smart charger, it reports that it is on fast charge. The tab has a much bigger battery than the phone.
 
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I use some thing like this
upload_2021-4-12_11-14-0.png
mine has two outputs but nearly the same, I have found in the main it is leads which cause the problems, I got some from Pound World and they only charge at 500 mA but same phone and same supply with different lead around 1.2 amp. Found Iphone seem to take full 2.2 amp, but nothing else on its own, I can plug in two Samsung phones and full 2.2 amp but one may get 1.8 amp but never seen full 2.2 amp.
 
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Some USB power leads do not have the data conductors, just the two power conductors. The device then cannot handshake with the USB power unit to set up the charging rate the power unit can provide.
 
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With my cheap Chinese 6Ah smartphone, it charges infinitely quicker with the supplied charger than any other.
 
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It seems a resistance in the cables tells some thing what power it can take, and the first USB plugs took less than the latter ones, but to look at they look the same leads, and we could not work out why some times the phone had charged and some times failed, so I bought the meter, and marked up bad charging leads, for data transfer no problem, but charging current was low.
 
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With my cheap Chinese 6Ah smartphone, it charges infinitely quicker with the supplied charger than any other.

Agreed there. It seems my newer charger has a 9V also for fast charging.

EDIT: That was the galaxy A40. My S21 didn't even come with a charger....or headphones or even a headphone jack. FKU Samsung.
 
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