Question: I am trying to find this information online for a while but I cannot find any precise info, thus Q on this community seems appropriate.

I would like to know if a [device](https://www.xtorm.eu/en/power-banks/xtorm-60w-power-bank-voyager-26-000/) having USB PD charging port (capable to charge with 60W) will be able to use USB QC3.0 charging speed capabilities well?

Maybe it is manufacture specific matter and I should not expect to be any rule here? Then I just need to write to manufacturer and ask it is in cas of that specific device.

Thank you

Answer: 
Assuming the lights are identical within a small tolerance, one has a very slightly higher resistance than the others.

With the same current in each, (as must be true in a series circuit) the higher resistance one will dissipate more power and heat up more : this further increases its resistance, heating it up further, increasing its resistance. Finally it may have twice or more the resistance of the other relatively cool bulbs, dissipating twice the power and glowing much brighter.

Measure the resistance of each bulb when cold.  

Measure the voltage across each bulb when hot.  

Compare the ratio of these voltages to the ratio of resistances when cold.
Assuming that the lights are identical, they should all be equally bright. Because the resistances are the same, the voltage is divided equally between them, each getting 1/3 of the battery voltage.

If they are not the same brightness, then they cannot be identical. Either one is somehow more efficient than the others, or one is higher wattage (lower resistance).