It's inevitable that there will be a time when your car battery is dead and you're not able to charge your battery with a charger. Battery jump leads can be cheap, but the quality is often poor, and they're unable to take the power needed to transfer electricity from one battery to another. While excellent jump leads are readily available, they are expensive, so making your own can be cost effective.
Purchase copper cable from your DIY store. Choose a heavy-gauge cable (AWG 4 to 8), and make sure you purchase at least 20 feet. Get 10 feet of red-coated cable and 10 feet of black-coated cable so you can distinguish between positive and negative. If you can't get different coloured cable, then purchase coloured insulating tape so you can wind it around the end of the cables.
Purchase four jump lead clamps. Get two coated in red plastic and two in black. Ensure they are heavy duty and can take the cable gauge you have chosen.
Strip 2 inches off the plastic coating from each end of the jump leads using a knife or large wire strippers. You will see many thick strands of cooper wire. This exposed wire will need to be fixed to the jumper clamps.
Remove the coloured plastic sleeve covering one of the clamp handles. Slide the plastic sleeve over the jump lead.
Use a large pair of pliers to slightly open the fixing bracket on one of the cable clamps. This will allow you to insert the cable into the clamp.
Slide the cable down the exposed clamp handle until the plastic coating on the cable is inserted into the bracket. Ensure the copper wire is inside the bracket. Use the same colour clamp and cable.
Squeeze the metal bracket together so it tightly clamps the metal wire. You need to use large pliers with reasonably long handles so you can get leverage. It's important that as much of the surface of the bracket and the wire touch each other to ensure that electricity is conducted properly. If the wires are not clamped tightly, then electricity will arc between the wire and clamp causing the battery clamp to heat, resulting in a loss of energy.
Use your pliers to squeeze the metal bracket around the plastic coating of the cable. Slide the plastic covering down the cable an onto the clamp handle. Pull the clamp and cable firmly to ensure they are fixed securely.
Repeat the process for the three remaining clamps. Test the jump leads as soon as possible using a car with a dead battery to ensure they work.
Always keep your jump leads in your car. You never know when you may need them.