Battery holder overheating

I am working on a project where I have various components connected to an Arduino Uno. These components are 2 LEDs, a keypad, buzzer, potentiometer, limit switch, LCD, and NO switch. In addition to these components I also am using 2 servo motors. My Arduino kit came with a 9V battery. I know that it is not enough to power the servo motors (I do not want to have it connected via USB to my computer).

I bought a 4 AA battery holder to plug into the breadboard. The leads were too small to fit in the breadboard so I soldered them to the jumper wires provided in my Arduino kit. To do this, I did strip about 1-1.5 inches of the battery wire holder which seemed to have a different material then the solid leads that were initially on the ends. I connected the red wire to the positive of the breadboard and the black wire to the negative. Then I also connected the Arduino ground to the ground of the breadboard. The problem I am having is that the batteries get VERY hot after about 15 minutes and I am not sure why. Is it because I stripped too much off the leads?

The original setup that I was using was plugging in the 9V battery to the barrel jack of the Arduino to power everything but the servo motors. Then I had the battery holder attached to the breadboard to power the servo motors. Since the AA batteries are overheating I am wondering if it would make sense to buy a AA battery holder with a barrel jack connector instead and have that as the sole power source for all my components and if this would be a better option to prevent overheating?

Essentially these are my questions:
1: Why do the 4 AA batteries overheat? (I even have a SPST switch hooked to the breadboard so its overheating even when there’s an open circuit)
2. Could I just buy a 4 AA battery holder to plug into the barrel jack of the Arduino Uno to power all my components? Would this option eliminate overheating since I wouldn’t need to solder?
3. 4 AA is what I read on an Arduino forum for a recommended amount. Is this too much? Could 2 AA batteries work as well?



Generally, a power source heating up indicates that it is sourcing more current. I do not expect stripping the leads and making connections like you described to create enough resistance to cause a significant increase in the current draw of your system.

Just to clarify, are you saying that even when the batteries are not powering your system (i.e. the switch is open), your battery pack still gets hot? If so, it sounds like you have a short in your setup somewhere.

If I misunderstood that, then I expect the servos to draw the most current from the components you mentioned. Do the batteries still heat up when you remove the servos? Additionally, can you measure the current draw of your system using something like a multimeter? In case you are not already familiar with how to do that, here is a link to a SparkFun tutorial that would be good to reference.

Lastly, can you post some pictures of your setup that show all of your connections?