In the system, separate ESCs are used for each thruster, but since Pixhawk has 8 pins and we use 12 motors, we use 8 motors as 4 pairs. For this, we combine the signal cables of two separete esc and use a single pin. ESCs are unidirectional and have BEC circuitry. There was a short circuit in the system. Also, while testing the thruster in q ground, slide mode does not work, only the thruster is triggered, full pwm is running and does not stop. We feed the system with 24 volts/6s.
Hi @ugurdemirezen, welcome to the forum 
Unidirectional ESCs aren’t expected to work with our normal ArduSub firmware, because it expects bidirectional ESCs and sets the ‘zero throttle’ point accordingly (1500us PWM pulse duration, which is at 50% throttle for unidirectional ESCs). If by “there was a short circuit in the system” you mean “all the thrusters started going and wouldn’t stop” then that’s likely the issue you’re running into there.
Assuming you’re using our T200 thrusters, note that they’re only rated to 20V. It’s possible to run them at higher voltages, but not recommended.