I have a Multiplus 2 3000 48V. I need 12V/50mA for an external circuit. The manual says that connector J pin 1 has 12V/100mA. Normally, its purpose is an external switch. Can I use this pin as power supply and connect this to my ciruit? What should I use as ground?
On multiplus-ii 5000 48, I used H main battery negative 
run a wire from G to D and use the aux relay to turn it off and on
if you use that J THEN YOU COULD DAMAGE THE INTERNAL systems so this would NOT be recommended at all
also if you use the aux relay you can turn it on and off via assistants, or even use the cerbo relay one then you can turn it on and off from the display.
If you use G for power, this will be at battery voltage 48v !!!!
If you use J pin 1 ensure suitable fuse below 100ma is fitted.
Good call to also use aux relay, gives options to automatically turn circuit on / off with assistant's if required.
