Does the spec actually say it has three cells? If it does, I failed to spot it.
The device clearly performs internal voltage conversions from the battery voltage to the required output voltage, which might be a source of interference. The target market seems to be cctv, I wonder if interference might be less of an issue, or more of an issue with, cctv vs vdsl modems?
Re mAh capacity, forgive me if I am wrong, but... is it not meaningless, unless they state the reference transfer voltage?
Specifically, if there are indeed three cellls, of (say) 1500 mAh each, and if the internal conversion were configured to produce an output voltage that matched that of an individual cell (approx 3.7V) surely it would be reasonable to advertise a mAh capacity of 3 times the individual cell’s capacity, ie 4500 mAh at 3V?
If that is correct, you can’t blame them for advertising the best case, which might be, say, an effective 4400 mAh at 5V (the lowest voltage available), assuming each cell is actually bit better than my example 1500mAh. But if the conversion is producing a higher voltage, say 12V, I reason that the real capacity would be just under a half of the ‘best case’ ie more like circa 2000 mAh.
I don’t pretend to be an authority or expert, just thinking aloud, won’t be offended if somebody wishes to explain that I am mistaken,