Battey pack question PLS HELP

[cyclopediatechtilon]

I am making the $50 robot.
The rc battery pack i got has two wires. after connecting it to the switch, how did they become three wires

[want2learn]

I don't really get what you mean.

If you are referring to the second (i think) photo down on the electronics page of the $50 tutorial, the switch has:
1- An input wire (from the battery pack)
2- An output wire (to your'e circuits)
3- a charge wire (for recharging the pack without having to remove it from the model)

N.B. The third wire isn't always for recharging, it can be a second output too.
Test them with your multimeter to see (or alternatively if you have no meter, hook up your battery pack, get a 4 or 5 hundred ohm resistor, solder it to an led and push the led tester into the pins and play about with the switch to see what you get (remember the led will only work one way round))

[Trumpkin]

Your battery pack should only have 2 wires (- and +) Admin put a three pin header because batterys usually have 3 pin molex connectors. The regulator has three pins, negative, positive, and output.

[cyclopediatechtilon]

But can i put a 2-pin header

[Trumpkin]

Yes.

[Webbot]

There is an advantage to using 3 pins for battery connectors as follows:-

1.  +ve
2.  -ve
3. un-connected

in that it means that you cannot accidentally plug the battery in the wrong way around

[cyclopediatechtilon]

Thanks a lot guys. 

[Ro-Bot-X]

There is an advantage to using 3 pins for battery connectors as follows:-

1.  +ve
2.  -ve
3. un-connected

in that it means that you cannot accidentally plug the battery in the wrong way around

Actually, the +ve is in the middle (pin 2) and GND is pin 1, so it is like a servo connector missing the signal pin.