This is how battery wiring works. There are two ways of connecting multiple batteries: Series and Parallel.
**Lets assume that each battery is 6V @ 4AH for simplicity sake.
Series: This is how you increase voltage. You take the positive end of one battery and connect it to the negative of the next. The positive on the second battery becomes your positive and the negative of your first becomes your negative. If you connect two like this, you get 12V but still only 4AH.
Parallel: This is how you increase amperage. You take the positive of one battery and connect it to the positive of another battery. You take the negative of one battery and connect it to the negative of the other battery. The positive and negative of either battery becomes your positive and negative(they are connected together so it doesn't matter) This configuration still is 6V but at 8AH.
Series and Parallel: You can put series configurations in parallel and vice versa. Just make sure each side is balanced. You can't but a 12V series in parallel with a 24V series, that will blow something up or at least melt some wires.
Now get to work making a battery pack.
