Test/review of USAMS Led display travel charger

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HKJ
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Joined: 05/24/2011 - 12:23
Posts: 7425
Location: Copenhagen, Denmark
Test/review of USAMS Led display travel charger

USAMS Led display travel charger
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Official specifications:


  • Brand: USAMS
  • USB Port: 2Ports
  • Plug: EU Plug
  • Product Weight: 60g
  • Dimensions: 88mm*50mm*23mm
  • Color: Black, White
  • Total Power: 11W
  • Input: 100-240V
  • Output: 5V/2.2A
  • Material: Fireproof PC
  • Feature: LED screen display
  • Protection: Insert Smart Circuit, Smart Identification
  • Certification: CE FC RoHS

I got it from a Banggood
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It arrived in a clamshell box with specifications on it.
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The box contained the charger, no manual or instruction sheet.
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Load current.
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Voltage, measured somewhere inside the circuit.
Measurements


  • Both outputs are auto code with DCP, Samsung and Apple2.4A
  • Outputs are in parallel.
  • Display turns on at 0.22A and turns off at 0.07A
  • Voltage is only showed when display turns on, when a load is applied the display will show the voltage twice and then only show current.
  • Power consumption when idle is 0.08 watt
  • Weight: 48.2g without accessories
  • Size: 82 × 42.5 × 24.1mm

Current
The current readout is fairly precise. It looks like the voltage readout is measuring voltage before the current shunt, i.e. it will show too high voltage when output is loaded.
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Output can deliver the rated 2.2A
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On either port.
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And also for both ports together.
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The current is the same at 120VAC
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There was no problem running for 1 hour at rated load, i.e. 2.2A.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.
Temp5126
M1: 55.6°C, M2: 36.0°C, HS1: 64.2°C
Temp5127
M1: 35.3°C, HS1: 46.3°C
Temp5128
HS1: 54.0°C
Temp5129
HS1: 53.0°C
Temp5130
M1: 43.7°C, M2: 34.6°C, HS1: 52.3°C
10ohm
At 0.5A the noise is 14mV rms and 260mVpp
5ohm
At 1A the noise is 17mV rms and 251mVpp
2.5ohm
At 2A the noise is 22mV rms and 229mVpp.
Tear down
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A bit pressure with my vice and I could remove the bottom of this charger.
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On this side is a fuse between the input terminals and a inductor (L1) between the two mains smoothing capacitors. The safety capacitor (CY1) and a small circuit board with the volt and ammeter.
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The unmarked chip to control the display and measure voltage and current is on a small circuit board together with the display.
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The first picture is a view to the inductor and safety capacitor, the second picture shows the fuse.
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On the second picture is the display and the two diodes to show what it is measuring.
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On this side is the bridge rectifier and the mains switcher (U1: FT8393). On the low volt side is the synchronous tectification chip (U2: FT8370B) and a resistor for measuring current (R15: R050), each usb output has their own auto coding chip (U3 & U4: UC2635).
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The distance is good, the black sheet helps with that.
Testing with 2830 volt and 4242 volt between mains and low volt side, did not show any safety problems.
Conclusion
The output power is fine for a charger with one output, but rather low for a charger with two outputs, especially when both outputs are coded for high current. The automatic coding works fine, the charger has low noise and I did not see any safety problems.
I like the current display and it is fairly precise.
The charger is a good usb charger for one high current device at a time.
Notes
Index of all tested USB power supplies/chargers
Read more about how I test USB power supplies/charger
How does a usb charger work?

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

Hobbyfotograaf
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Last seen: 2 months 4 weeks ago
Joined: 02/11/2011 - 16:25
Posts: 382
Location: Belgium

Thank you for this review.
I bought 2 of these (flash deal at Aliexpress for 4,08euro/pc), but i was not sure if they are safe.

I don’t have all the measuring equipment that you are using, but i do have a UNI-T UT502 insulation resistance tester, i tested both USB chargers at 2500V, and there are no problems with the insulation.
That is the first test that i do on all Chinese import things that work on 230V, before plugging it in.

HKJ
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Last seen: 4 days 17 hours ago
Joined: 05/24/2011 - 12:23
Posts: 7425
Location: Copenhagen, Denmark
Hobbyfotograaf wrote:
I don’t have all the measuring equipment that you are using, but i do have a UNI-T UT502 insulation resistance tester, i tested both USB chargers at 2500V, and there are no problems with the insulation. That is the first test that i do on all Chinese import things that work on 230V, before plugging it in.

That is a good test, it will catch the worst stuff.
In my experience 2500V is a bit too low to catch 1000V ceramic capacitors used instead of safety capacitors. The problem with the 1000V capacitors is that one time over voltage will permanently lower the insulation resistance. A real safety capacitor looses capacity, but not insulation resistance due to over voltage.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/