USB Load resistor 2.2-4.7-10-20ohm with fan

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Official specifications: I got it from Banggood

The most interesting detail about this type of load is how hot they get, some power resistor has a working temperature between 200C and 300C when fully loaded. Due to the fan this will hopefully have more moderate temperatures, I have tested a version without fan before

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The load was in a plastic bag, no box or instruction sheet was included.

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All the leds works in parallel with a single resistor. The led at the usb connector is on when power is connected and uses about 0.7mA at 5V. The other leds will turn on when the switch for that resistor is turned on.
The fan is in parallel with the power input and there is a series resistor that can be switched in or out for low or high speed.

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The grid protecting the resistors is a good idea, even with the fan they can get hot.

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Load testing


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Being a resistor the current will depend on voltage, but the fan add some extra current. This is most obvious at low current draw.

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At high speed the fan will draw more current.

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Here is the fan current at low and high speed. The fan do not like above 6V, notice how the current draw increase dramatic in high at around 6V.

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The low fan speed is best used for higher voltage input, here I have tested 10 & 20ohm resistors with up to 15V input. I would not recommend using the two lower values with voltage above 5V. The ticks in the curves are from the fan, in it unstable below 6V when on low.

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Due to the fan there is a small variation in current, especially at the start where the fan needs more power to start.



20ohm resistor high fan speed

Temp5464

HS1: 35.7C

Temp5465

M1: 31.6C, HS1: 45.4C



10ohm resistor high fan speed

Temp5466

HS1: 36.7C


Temp5467

M1: 36.1C, HS1: 73.8C



4.7ohm resistor high fan speed

Temp5468

HS1: 45.4C



Temp5469

M1: 42.5C, HS1: 117.8C
The temperature is perfectly fine for the resistor.


2.2ohm resistor high fan speed

Temp5470

M1: 35.5C, HS1: 96.6C


Temp5471

M1: 50.4C, HS1: 179.4C
Even this is fine for the resistor.



All resistors high fan speed

Temp5472

M1: 45.5C, M2: 35.6C, HS1: 111.6C
The resistor get hots here, but not too hot for this type resistor and protective metal grid reduces the risk for nasty burns.

Temp5473

M1: 122.9C, M2: 80.1C, M3: 48.9C, M4: 52.8C, HS1: 165.3C



20ohm resistor low fan speed at 12V

Setting the fan speed switch to high will probably destroy the fan!

Temp5476

HS1: 73.3C

Temp5477

HS1: 129.2C
The temperature on the resistor is acceptable.



10ohm resistor low fan speed at 12V

Setting the fan speed switch to high will probably destroy the fan!

Temp5478


M1: 38.6C, HS1: 66.5C

Temp5479

M1: 54.3C, M2: 54.5C, HS1: 273.9C
Here the temperature is a bit too hot for the resistor.



Conclusion

With the added fan the load can handle much more power without getting too hot, some of the resistors can be used at higher voltage, but it is very important to switch the fan to low speed.
Due to the fan the current draw is not very precise, but as long as a usb meter is used to calculate mAh it is good enough.

This load is fine for testing mAh on power banks (with usb meter) or doing longer load test on usb chargers.



Notes

The device was supplied by Banggood.com for review.