A car battery is made up of smaller individual batteries or cells. These cells are stacked on top each other so that the positive side of the first cell is connected to the negative side of the second cell. This is called a series connection. When batteries are connected in series, the voltage of the two batteries add up to make a bigger battery. If you have two six-volt batteries, you can connect these two batteries in series to make one 12-volt battery.
Clean both battery posts on both batteries. Verify that the post are clean and free of corrosion, oil and dirt. Verify that the batteries are in good condition and the outer walls are not damaged.
Place the two batteries side by side. The positive terminals of both batteries should be on the same side.
Use cable cutters to cut a piece of battery cable. The cable should be long enough to reach from the negative terminal of one battery to the positive terminal of the other battery. Use a sharp knife to score and cut the insulation from the cable. Connect the battery cable terminals to the new cable.
Connect one end of the new cable to the negative battery terminal on the left-hand battery and connect the other end to the positive battery terminal on the right-hand battery. Do not connect the cable to the positive and negative terminals on the same battery.
Connect the existing battery cable to the positive battery terminal of the left-hand battery. Connect the existing negative battery cable to the right battery.
- Jupiterimages/Photos.com/Getty Images