Car charger 5V-3.1A Dual USB

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Official specifications: I got it from ebay dealer: original-cafele-3c

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It arrived in a plastic bag inside a envelope, no instruction sheet included.

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Measurements

Voltage Current

The voltage display is precise, the current it not perfect at low current, but gets better at higher currents.

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The charger can deliver about 4.3A on output #1

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And the same on output #2

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When used together it is also the same.

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Input voltage do not affect output current.

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It works down to about 7V

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Efficiency is fairly stable on the actual working ranges.

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Current consumption goes down when the display flashes.

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It worked fine with 3.1A for one hour.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.

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M1: 44.9C, HS1: 62.1C
It gets fairly warm at full current.

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M1: 53.8C, M2: 48.1C, HS1: 58.9C

10ohm

Noise at 0.5A output is 15mV rms and 104mVpp

5ohm

Noise at 1A output is 21mV rms and 204mVpp

2ohm

Noise at 2.5A output is 22mV rms and 221mVpp, all nice low values.



Tear down

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It was easy to tear down, I could remove the front with my fingers.

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On this side is two capacitors and a inductor. The front panel has both 5V and 12V connection due to the voltmeter.

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The is one buck switch (U1: HC2017) that is designed for car USB power supplies. This means the chip has build-in USB auto coding, but it is not used here. The charger uses a zero ohm resistor as fuse.

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The front circuit board has the two USB connectors, a display and a unmarked voltmeter chip.
There is also four small blue leds around the perimeter

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Being a 12V device there is no need to test with high voltages.



Conclusion

This is a cheap and simple charger and can deliver too much current on a single USB connector, but for the price is it a fairly good car charger, the volt and current meter is a nice addition.



Notes

Read more about how I test USB power supplies/charger
Compare car chargers and other DC supplied chargers