3d4real wrote:the problem is the cable. I need at least 2 meters, so I want to plug in a micro USB cable.
An "ordinary" USB cable of >=2 metres could give you additional problems (too much resistance). Better to cut the provided cable and "splice in" an extra length of equivalent cable. The power supply only uses two low, resistance wires for power - a standard USB cable, of similar thickness, will have extra wires and the wire resistance (per unit length) will be higher. More to the point of the suitability of the device - a charger
the same as a power supply
- they do different jobs. A power supply has to supply a "fixed" voltage (for the Pi ~5V) over a large range of current draw, down to a minimum voltage at the maximum current, including cabling losses (for the Pi ~4.6V). A charger's voltage can be allowed to drop more rapidly, it only has to be "just high enough" above the battery's voltage due to the present charge level to maintain charging current to flow (for a typical 'phone battery that's ~3.8V). You can find quite a few measured examples of both "loading" behaviours within my webpages starting here:
http://www.cpmspectrepi.uk/raspberry_pi ... plies.html
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm