Juwei charge accelerator J7-i (j-k)


Official specifications: I got it from Aliexpress dealer: ETORCH Design Manufactory Co.,Ltd store



Behind the W numbers are leds, but the scale is not a very reliable power indicator: Drawing 2 watt but 3W & 6W is light and 9W flashes.



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During these tests I limited my power supply to 4A and placed a capacitor on the usb connector feeding current into the device. Without the capacitor it did not work reliable.


The output voltage is a bit high, this means most devices will charge a bit faster. I could draw 3A, but look at the noise (Further down).


The device can boost voltage and do QuickCharge, here I got up to about 1.8A before it dropped out because my power supply limited current.


At 12V I got up to 1.3A before my power supply limited current.


Here I played a bit with QC2 and QC3, it works nearly expected. I did see a few unexpected voltage shifts, but I do not know if it was due to the tester or the device.


There is no problem maintaining the rated 1A current.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.


M1: 39,7C, M2: 39,6C, HS1: 67,8C
On this side it is the inductor that is making the heat.


HS1: 72,9C
Here one of the transistor helps the inductor making it warm.


Noise at 0.5A load is: 7mV rms and 70mVpp.


Noise at 1A load is: 10mV rms and 94mVpp.


Noise at 2A load is: 127mV rms and 496mVpp. Here it is starting to get bad.


Noise at 2.5A load is: 223mV rms and 1524mVpp. And totally hopeless, this is not due to my current limit.


Noise at 9V and 0.9A load is: 20mV rms and 145mVpp.


Noise at 12V and 1.2A load is: 326mV rms and 1311mVpp. Draw a little bit to much current and there is lots of noise, again it is not due to my current limit (It was tried with both 4A and 6A limit and looked the same).

Tear down



On this side of the circuit board is the microprocessor, a transistor, a inductor and the power scale leds.


On this side is two big transistors, a switcher and the QC3 controller. There is also a 0.01ohm resistor in series with the output (The switchers has its own 0.01ohm resistor), making it possible to measure the current.




It is an interesting device, but where can it be used?
The answer is multiport chargers without individual current limit and then with QuickCharge devices.
But do not use it on weak chargers, only on chargers that can deliver enough current!

The device works as advertised, but it requires a very powerful usb charger to work and it do overload the usb connectors. It must also be used directly in the charger, do not put a cable between this device and the 5 volt source!

I will not really recommend this device, it can be used, but a good charger is much better.


Read more about how I test USB power supplies/charger