Smoked pixhawk 2.4.8 connecting battery

Ok I have had my pixhawk powered up on usb a few times no issues while I was waiting for parts to arrive. Got everything I needed and started the build. Motors got calibrated and soldered on the distribution board. Power module connected via xt60 to the distribution board and I powered up the pixhawk. No problem

Then I connected the motors to the pixhawk. Hobbypower simonk 30a. With the bec power wire still plugged in. I was already to calibrate. I plugged in the battery and a few seconds later magic smoke from the pixhawk

Before I hooked up the esc’s to the pix I read and saw on the sight that they connected all three wires.

But by not disconnecting the bed wires did it fry the pixhawk?

I need to know why before I by another. Don’t want to smoke another

More info. Disconnected the pix. Motors and esc still connected to the distribution board. Plugged in battery and powered up gimbal to calibrate. After I was done…about a minute or so I noticed #3 esc was getting very warm. The others were cold

Got the volt meter and checked the bec power 12.2v at the servo lead. Checked #1 esc…5.39v

Would the surge of the 12v cause my issue?

Sure sounds like the BEC failed in that ESC and is now passing battery voltage. More importantly, why do you have multiple BEC hooked to the same servo rail? You have to pull the middle wire from 3 of the 4 ESCs so the multiple regulators don’t try to feed eachother.

Yea not the brightest thing I did. I should have pulled the red wires. Quick start guide shows all three hooked up and said so.

I just want to be sure that the bad esc was the problem before I hook up another fc and new esc’s

I just don’t know how the voltage works on the rail. 3 esc’s @5.4v 1 @ 12.6 and a power module @5.5v. It makes sense that it smoked But I need to know for sure by somebody much smarter than me

I pulled this from Ardupilot
“ Voltage ratings

Pixhawk can be triple-redundant on the power supply if three power sources are supplied. The three rails are: Power module input, servo rail input, USB input.

Normal Operation Maximum Ratings

Under these conditions all power sources will be used in this order to power the system.

Power module input (4.1V to 5.7V) [refers to the voltage coming into Pixhawk from the power module]

Servo rail input (4.1V to 5.7V)

USB power input (4.1V to 5.7V)

Absolute Maximum Ratings

Under these conditions the system will not draw any power (will not be operational), but will remain intact.

Power module input (0V to 20V) [refers to the voltage coming into Pixhawk from the power module]

Servo rail input (0V to 20V)

USB power input (0V to 6V)”

Under max ratings servo rail 20v? Looks like I had close to 30v if it is a collective voltage in series

Yes or no?