Today I am testing two small devices capable of temporarily backing up the power supply of a 5 or 12 V receiver in the face of an unexpected power outage. The first is a distinctive black box plugged into a USB cable, necessarily operating on 5 V only. The second is slightly larger, resembles the router itself in size, operates on 12 V and has 5, 9 and 12 V outputs.
Let's start with the first one - you can vainly find the model name here, but you can also judge a lot by its appearance. The whole thing is quite expensive, costing £100, and advertised as it is as a "UPS for alarms". The rated capacity is 20 Wh, according to the seller.
The manual is in Chinese, although it manages to read something about a 500 mAh battery capacity. This is strange, on the case it says 5000 mAh. I also see separately the capacity given in Wh, but how come it is from 14.8 Wh to 57.52 Wh?
I charged the whole thing to full, still checking with a USB Doctor meter that I was sure the current draw had dropped significantly. I additionally left it overnight and then measured the capacity with a test load at 1 A.
The output is 4.5 V at 1 A current, the input is over 5 V and 1.25 A current. This already tells us about the efficiency of such a gadget. With no load (when charged), 0.05 A is drawn.
I measured the capacitance in the same way, I repeated the test several times, but the results are unrelenting.
1.6 Ah at 5 V gives about 8 Wh. You could still convert to battery capacity at 3.7 V - 8 Wh/3.7 V ≈ 2.16 Ah, or about 2160 mAh on the cell side (ignoring losses on the inverter; in practice it will be a little less, e.g. 1900-2000 mAh available at the output). Well... that's less than half the promised 5000 mAh. Then again, the 500 mAh in the instructions is rather an error, as the translator suggests charging current.
The first UPS didn't impress me, so maybe the second one will be better?
The second model was even more expensive . We paid a good £150. The seller promises a capacity of 32.56 Wh - we will check.
The set is undoubtedly quite rich. Should that justify the price? In addition, there is also a Polish-language manual. The distributor's contact details are also given there, so we know who is responsible for importing this invention.
The device draws up to 10 W from the mains when charging without a load:
More than 2 A at 5 V can be drawn:
As before - charging to full and testing. For consistency, test at 5 volts.
Let's say - 6 Ah at 5 V, or 30 Wh. Here the result is already more in line with expectations, although also a little too small, the error being within 7%.
In summary, a black UPS bought for £100, the one plugged into the USB cable, has a capacity of about 8 Wh, and a white one, for £150, the versatile one (5, 9, 12 V), has a capacity of 30 Wh. It seems to me that this was not a very good deal. In the case of the white one, it's not a tragedy yet, because I also basically knew what I am buying (the seller announced 32 Wh), while the black one has only 40% of the declared capacity, which I find unacceptable.
As for the rest, I have no complaints, the current capacity is in line with the announcements, I also did not notice excessive heating. Inside the equipment I have not looked, because it would require a clear damage to the casing, there are no screws and the whole thing is not built to replace the cells, which in total I also consider a minus.
Was it worth it? Well, probably not though.... anyway, now you know what to expect from the little black box.
Or maybe I was just unlucky and came across a bad unit? What experiences have you had with UPSs for routers and alarms?
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