Might be huge current...
But, Vin pin is connected to onboard regulator - isnt it? So i have to power lcd backlight out of arduino?
I will try to use DC-DC step-down, cause instrument should be powered from 12V battery. Also I have High Voltage converter for 12V and it consumes huge current.
How much current does SD card consumes? I have a converter that provides 5V 500mA from 12V, would it be enough for MCU and SD?