Every so often check the external length of each battery cable for any signs of damage or a damaged or burnt insulation and corrosion because it is common to find poor connections and starting problems that would reduce performance. Inspect the cable to terminal connections to see if they have cracks or if the wire strands are loose or corroded; any white, fluffy deposits under the coating should be considered to be corrosion and the cable should be replaced. Normally, the negative cable should be disconnected from the negative battery terminal first and reconnected last to prevent making shorts inadvertently. First unhook the ground cable from the negative terminal and then the positive terminal thereafter remove the other ends of the cables, the one that is connected to the B+ terminal in the engine compartment fuse and relay box, the 
Alternator and the starter motor solenoid. When replacing the cables it is advisable to take along the originals to get new corresponding ones as the positive ones are usually red and larger than the ground cables black and smaller. It then may be necessary to clean the threads of the starter solenoid or ground connection with a wire brush and apply a corrosion inhibitor or petroleum jelly to the threads before making the connection of the cable to the terminal. Make certain that a new cable extends to the battery post without extension, and after that, attach the negative cable on the negative post of the battery.