I need to power an enclosed Arduino Fio project with 12V. The intention is not to attach a battery because there is no need as this is a fixed installation with a 12V DC available (for a pair of relays which will be controlled by the Fio).

My question is what Pins should I use. The Fio page (https://www.arduino.cc/en/Main/ArduinoBoardFio) on the Arduino web site says...

Input Voltage 3.35 -12 V Input Voltage for Charge 3.7 - 7 V

Unfortunately, there is no indication what pins these specs refer to. I assume that the "Input Voltage for Charge" refers to the mini-USB port and unlike other Arduino boards, there is no Vin pin to supply the board externally. Looking at the board layout on the same web page, I think the only possible option is via the two pins in parallel to the battery port which I suppose are then going into the voltage regulator on the board.

Any comments or suggestions? Has anyone done something similar?

  • Check the schematic. You can connect the voltage the the JST battery connector, or JP3 (I'd double check those two holes are connected to the JSP using a mulimeter). But I'm slightly doubtful about that 12v rating they give on the webpage. The voltage regulator can handle that, but I don't think the battery charger IC (MAX1555) can handle 12v on the BAT pin, looking at the datasheet.
    – Gerben
    Commented Jul 4, 2015 at 19:10
  • Max1555 can only handle of 7v input (see datasheet). Based on the schematic, I won't trust the info on the website. I think it will be better and easier for you to find a power supply of 5V with micro USB. Even if you use the 12V supply applying to JP7, there will be too much voltage drop on the 3V regulator that it will generate heat than it should be.
    – hcheung
    Commented Mar 4, 2020 at 7:22

1 Answer 1


I used the external switch input JP7-1 for 12v, any GND hole, and make sure the switch is off. This bypasses the charge circuit which doesn't like 12v.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.