Using an Arduino on a motorcycle I want to use the Arduino to control various electronics on my motorcycle. I would need to power the Arduino with the motorcycle battery. So the question is, when the motorcycle is running the alternator will be putting out something like 13v to the battery. So can I still just connect the battery directly to the vIn and ground to power it?
Accordly to Arduino Technical Specs:

-Input Voltage (recommended)    7-12V

-Input Voltage (limit)  6-20V

https://www.arduino.cc/en/main/arduinoBoardUno

Another Arduino thread:
https://forum.arduino.cc/index.php?topic=22676.0

I would say a better choice is to use another battery power supply just for Arduino. Is is easy to install, easier to handle and more verstile unless you really needs to use your motorcycle battery. And if you want or need to read your motorcycle battery just use a portable voltage meter plugged onto Arduino with no need to use your vehicle battery to power it.