9V Battery pack causes my Arduino to overheat.

I have 6 triple A's in my battery pack and it causes my Arduino to get really hot. I'm wondering if I just got a bad board or ?. It seems to run nice and cool when hooked up to the USB.

Thanks in advance!

What is connected to the board? When connected to USB the 5V regulator is bypassed. When the 9V is connected to the power plug or Vin and no USB, the voltage regulator is active. The power that must be dissipated by the regulator is 9V - 5V times the current drawn through the regulator. So the more current drawn through the regulator the more heat must be dissipated. A couple hundred milliamps and the regulator will get toasty, too much will trip the thermal cutout.

Thanks for the quick response! Just the battery pack, but my batteries are brand new. At one point I had the USB and the battery pack connected when I first started and was wondering if maybe I burnt something then thats letting it heat up now? Thanks again!

Uno, Mega, Nano. There are many different ones. How did you connect the batteries. To the DC socket, or a pin. Did you use the V-in pin or DC socket. Do you know what gets hot. Leo..

My apologies. I didn't even realize I wasn't very informative about my specs in the first post. It's an Uno R3. I connected the batteries to the DC socket. I think it's the little green chip beside the USB input.

The 3-pin chip with small heatsink tab next to the DC socket is the 5volt regulator. The green square thing is the polyfuse. Which one gets hot.

Is the USB cable unplugged when you are on battery power? Leo..

So nothing connected to the Arduino and no USB connection. One has to wonder what code you can be running.

Are you using alkalines @ 1.5V or rechargeables Ni-Mh @ 1.2V? I would try running them 3S2P (3 series in parallel), doubling the capacity and halving the voltage to 4.5V and 3.6V respectively, it would be out of spec at 16Mhz but should run just fine and without the heat from the linear voltage regulator.

Or just use 3xAA instead or a single lithium cell/lipo pack

And connect it to the 5V pin directly to bypass the regulator