I have recently started tinkering with technology to see how things work. I am building a small box with a phone charger, flashlight and solar panel however I wanted to add a laser pen. After taking it apart enough, I can't understand how it gets power from the 2 batteries in it, here is the pen, where would I connect the red and black wires to power it from my battery?
Similar to a flashlight, one battery contact is the outer metal case and the other contact is the center. A laser diode will be sensitive to polarity. If you still remember which way the batteries were inserted before the teardown, the tab at the end of the PCB is the inner contact for the center battery terminal (most likely positive I'd guess).
You do promise to be careful not to burn your eyes out with what is presumably a Class I laser device, right? Wikipedia Laser Saftey is required reading.