It is not dangerous. Voltages above 5.25V may be dangerous, it depends on the phone (I would not expect any danger below 5.5V). High noise levels may interfere with the touch screen and with receiving, but it will depend on the frequency content and level of the noise and how sensitive the phone is for noise. It is not dangerous for the phone.
Any chance you will disassemble the powerbank to take a look at the internals? Anyone seen the PCB before? No idea why the PB is designed so large with so much space wastage on battery bays (the sides). It could be very much smaller.
I would want it a bit longer in the bay to accommodate button top cells. And the worst flaw of all is its inability to charge low draw items, ie: Nitecore TIP/TINI/Tube, Sansa/Sony MP3 players, UltraTac K18 mini charger, MecArmy SGN5, and anything drawing less than 300mA.
Not handy at all on a long trip. Why did they limit it so?
UPS is “uninterruptible power supply” and means the device will switch smoothly between input power and battery and back again to always supply output power.
Okay, I understand what a UPS is. What I don’t understand is where you said it turns off when USB power is removed. Do you mean that it turns off briefly or turns off completely, and something has to be done to turn it back on?
If input to the Xtar drops, then recovers, the Xtar will carry on charging as before, but the output of the Xtar to a connected device will drop, and not resume until the Xtar button is pressed.
2A output is important for me. Can you recommend a similar power bank that has lower noise.
Doesn’t have to be 2 cells. 3, 4 or more cells would be even more great
The diagram and comments below are an excerpt from the HKJ report above.
Can one infer from this diagram that the efficiency for the PB2 with one cell averages about 88%? Can one also assume that the efficiency will be about the same with two cells?
Efficiency will be best with highest input voltage and fairly low current drain (How low depends on the consumption of the circuit itself), I would not expect much if any difference between one and two cells.
The problem measuring efficiency is that I need to measure the battery current, this requires I put something between the battery and the boost converter in the box. I have only made one sensor for this, if I wanted to do it for two batteries I would need two sensors and four voltmeters on the battery side (Or open the box and mount a resistor between batteries and boost converter).
HKJ, thank you for the quick reply - and your good, hard work. Could you make a qualitative assessment of the PB2 power bank USB out efficiency in comparison to others that you have tested? Would you say it Is above average, for example? What do you think of the manufacturer's claim of up to 92% efficiency? Thanks.
The 92% sounds about right, the numbers in my logfile says 91.5% at the start. There is some tolerance on my measurement, the usb cable and connections will add resistance and my 10ohm load resistor is 0.3% too high.
I cannot remember the efficiency of the different power banks I test, you will have to find them and compare the efficiency curve, but it is better than Soshine E4S.
Is it possible that in future tests, you also give a few efficiency percentages at different loads if you happen to know them as ‘byproduct’ of your tests?