We would like to use 12 T200 thrusters, each with a separate BasicESC. The input power will be coming from power supplies and since each need about 22A max, we are going after commercial products. The problem is that power supplies come in 15V or 24V by standard and we could not find any with 20V that has a high current output, in our case about 270A in total.
We decided to go for 15V, and in this case, we will be limited to 15*22=330w max power which is fine considering the max power of each thruster is 350w.
The problem is voltage drop over 5x2 meters of round trip, which is around 1.5v for a 3x2.5mm2 cable. Is this still a reasonable range for the function of ESC or should we go for a thicker cable?
For example, if we go for a 3x6mm2 cable we will have a voltage drop of about 0.62v with the cost of extra weight and thickness of the cable.
Your math here is accurate, and only 1.5V of voltage drop will work fine. Although not ideal from an efficiency standpoint, this will not hamper the operation of the ESCs or thrusters. The ESC will operate just fine down to 6-7V or so. That about as thin as you would want to go however, as the wire will heat up and you will be losing a fair bit of power (400W) in the cable. As long as it is kept cool/has high temperature insulation, this should be alright. If these thruster will be run at constant high throttle, I would recommend the thicker wire option to increase efficiency and reduce wire heating.
I also think that the thicker wire would make more sense. I think I was not clear in the first post that we would like to put the ESCs close to the power supplies and then have 5 meter of cables from ESCs to the thrusters. Is this still fine for the controllers/thrusters setup?