Just confirming that it is ok to power a Boron using 12v on the VUSB pin?
The docs don’t mention this but it is alluded to in forum posts here
Yes. 12v should work on VUSB. I still don’t like how this is never stated explicitly in the docs. You would have to review the Boron schematic on your own and look at how the PMIC (BQ24195L) is connected to the board pins. Then you have to pull the BQ24195 datasheet and look at what that maximum spec is.
Here you can see that VUSB labeled on the board is VIN on the schematic:
Here you can see that Vin is directly connected to the BQ24195L VBUS pin:
Normal operating voltage for the BQ24195 is 3.9 to 17 volts. Maximum rating is -2 to 22 volts. The capacitors on Vin are spec’ed at 25v and it looks like the VBus diode can handle 30V. So in conclusion, you should have no problem powering the Boron by 12V DC. You may even get away with up to 17V or so… but at your own risk.
EDIT: @RWB makes an excellent point below, the higher the input voltage, the more heat that is generated. You must take great care as to not overheat the board when using out-of-spec voltages which is probably why it is only recommended up to 12V.
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I’m curious if you can more fully describe your “12v” power supply needs? Are you asking re: an automotive deployment?
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The higher the input voltage the more heat the chip and inductor will generate while charging and bucking the higher input voltage to battery voltage.
Make sure the board does not get too hot while charging and if it does you may want to limit charging current to 500ma max.
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I want to power the Boron using a Car battery. Although I know car batteries are around 14.x V so I will probably need a buck converter but trying to keep the solution as simple as possible.
All I really need is for the boron to send an alert when our zimmatic irrigator throws a fault, so I was going to hook up a buck converter and lipo so that when there is a high signal (12v) the boron sends an alert.
You will be fine by powering directly from the battery but just limit the battery charging current to 500mA to keep the voltage conversion heat down. There is code on the forum that shows how to change the charging current and that will need to be placed in the setup() loop so it runs every time the Boron starts up.
Using a Buck converter to go from 12v to 5v is another option but adds cost and a extra thing to buy.
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Powered from a car battery or powered from an actual operating car’s 12 v power supply? Reason I ask … automotive 12v power environment is a much more complex kettle-o-fish. I too would be interested to have an off-the-shelf Boron power solution for 12v automotive. Useful background info here … http://forum.arduino.cc/index.php?topic=213399.msg1649634#msg1649634
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I’m using 4 of these to convert a 24v battery bank to 5v to power some Photons.
I put an oscilloscope on the 5v output and it never goes above 5v even when I feed it 26v and turn the power to the buck converter ON.
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This might be a stretch, but worth mentioning. If your Alarm Condition is when you see 12V, just use that voltage to Boot the Boron and send a Publish, ......? Nothing else required.
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Oooh, and they have a 10A version of that converter, too! That will be great for some lighting projects I had in mind for my car. 
I can confirm that a 12V battery ( was almost @13V) will fry a Xeon if ran through the VUSB. Not sure if same would happen on a Boron? I’m no electrical engineer. Please share if anyone has tried this with a Boron with success!?
12V on a Xenon or Argon on VUSB will be immediately fatal to the device. Also do not power both VUSB and the micro USB connector at the same time on a Xenon or Argon.
12V on a Boron on VUSB will be OK, as long as you don’t have any other circuitry that is expecting VUSB to be 5V maximum. The reason is that the Boron has a more elaborate power manager IC (PMIC) that is basically the same as the Electron and E Series and can tolerate higher voltages.
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I have used a number of the Traco units to go from 24 volts down to 12, 5, or 3.3. I really like how small they are if you are going to use this on a PCB. Just thought I would throw them into the mix.
Cheers,
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