Two 9V in Parallel Power Supply

[rainyshadow]

@SteveMann

The 9V batteries that Paul ghosts are fine for a short classroom demonstration, but the mAh rating of the 9V battery is so low that it would have to be replaced daily. Not very practical for a working project. A better solution would be to use a 12V battery (like a 4S LiPo) and a DC-DC buck converter to get 5V for the Arduino board.

Oh, so it was about the practical side.

I thought there may be some kind of incompatibility that may damage the device, lol. The only possibility i could think of was if those are some fancy rechargeable batteries with built-in boost converter, whose working frequency would cause interferences