Smoke when turning the power on

[MarinLGU]

Hello everybody,
I'm new to the OpenMarine community, as I'm trying to use my RPI4 + McArthur HAT (including power volume) + Maiana blue AIS together. I could do a successfull test 10 days ago in my boat by powering the HAT with the black pins (12V direct to battery) and the 12V SW. 
Yesterday I re-iterated with two notables changes 
1) I used a "new" RJ45 cable to connect Maiana (in fact I cutted the cable and add later a new connector by myself in order to travel the cable in the boat)
2) Meanwhile, I was charging the boat so the tension of the electrical circuit was 14,2V

When I turned the switch 12V SW on , the 12V and 5V LEDs turned on but almost immediately I could smell and see smoke coming I think from the raspberry more than the HAT. So I immediately turned the switch off

I retried after disconnecting the boat from shore power (battery tension was 13,1V)  and the maiana AIS , the system started  and worked (I could connect to Openplotter through VNC) but the Pi was very warm and then turned off automatically. I also tried to connect the Maiana RJ45 but none of GPS or AIS LEDs blinked.

So I have two hypotheses : 
1) I did a mistake while re-wiring the RJ45 connector, and this explains both the GPS and AIS not working and the overheating
2) The high tension in the battery due to charging and the recent charge caused the overheating and a mistake in rewireing the RJ45 explains the GPS and AIS not working.

Do you have any idea on what could have happened and how to debug further what's happening? 

Thanks a lot,
Best,
Marin

[Adrian]

The MacArthur HAT has an over-voltage protection, that starts to kick in above 15.6V (D1). Even when exceeded, the worst that should happen is a damaged D1. The 12V would be shorted to GND, causing a fuse to blow. In no scenario should 12V find its way to the Pi.

MAIANA has a similar protection in its 12V input.

Mistakes in wiring the RJ45 can put the 12V on the wrong pin inside MAIANA. Hard to predict the result of that though.

Also a common mistake is to insert the 12V screw block into the wrong connector, which can have fatal consequences for the Pi.

[MarinLGU]

Hi Adrian,
Thanks for your reply.
I think we can roll back the hypothesis of 12V into the wrong connector as HAT's 5V and 12V leds turned on ?
Then, I will try to debug that, understand what appened.
Best,
Marin

[Adrian]

I would first check the 5V output on the MacArthur HAT without plugging it into the Raspberry Pi. Just connect GND, 12V and 12V SW and then use a multimeter to check for 5V on pin 2 of the 40-pin header. You could also make an RJ45 pig-tail and check whether 12V and GND are on the pins/wires you expected.