for my project I want to use 13 meter WS2815. Power supply will be 150W / 12.5A.
I’ve read a lot about power injection. The length of the data line should also be limited. That made me a little insecure.
For testing I only connected the 14 meter WS2815 to the power supply at the front.
The data line is 10 meters long (0.75mm2)
It works perfectly at the desk. I couldn’t find any restriction.
Will the evil devil catch up with me later?
Most injection talk is for 5V LEDs.
Your power may be fine, but I’d do some extensive testing on the bench before I was certain - Make sure you can achieve your desired brightness on solid white and that it doesn’t dim or flicker as it gets farther down the strip
As for your data line, 10M is gonna cause you an issue at some point down the road. You’re definitely going to want to use level-shifters, and likely the 33Ω series termination resistor as well. You may want to consider using the max485 modules to convert the data signal to rs485, which is a 2-wire protocol that’s much less susceptible to induced noise and transmission line reflection. You would need 2 per data pin, one after the esp to convert, and one before the LEDs to convert back.
I had artifacts appear on the WS2815 tape after 6 meters, the wire is 0.5 mm2
I didn’t notice that, wrong glasses on 
I am new at this so not sure that I am ready to offer advice, however, I have some experience with a similar setup. I am using about 13 meters of the WS2815 as well as a 150 watt power supply. In testing in my basement, I saw no visual degradation at 5 meters, but did see very minor drop at 10 meters. For my install I chose to connect the power at one point only, however, that was near midpoint (ie. about 6 or 7 meters running each way from the connection. I did use 18 AWG wire, however, my cable length is only 3 or 4 feet. I then connected my controller at the one end, where it sourced its power from the strip. I am seeing no problems.
I am assuming that your strips (like mine) are 30 pixels per meter.
Don’t know if this helps - just sharing.
Quarks - a correction in my previous info. I actually used only a 60 watt supply with there being just over 200 pixels at .3 watts per pixel. Confused it with the supply I got my son-in-law for a longer string where we made two mid string connections (about 1/4 of the length from each end - no pixel being more than a quarter length from a power source). His work great as well (using canned SP108E controllers).
Here is someone’s test of 20 meters powered from one side
Upd. Realized that connection on this video from both sides. Powered by 5V3A power supply
