Battery terminals which are corroded can cause more problems than just poor starting. If there is blooming corrosion taking place on the end of the battery terminals, it is a sign that your battery needs to be changed. However, Minor corrosion should not be avoided as it can reduce alternator output by 30%. This can cause early failures by affecting your charging system. To begin with, slower cranking is caused due to extra resistance and premature starter failure and overhead starter motor windings can occur inside the vehicle. Old corroded terminals can be replaced in order to prevent premature failures. The process of doing this is very cheap and the job is very easy. Remove and clean the battery posts and terminals if they have minor corrosion with a wire brush. Baking soda or water solution can be used to neutralise the battery acid. A battery terminal spray cleaner can be used by drying off paper towels; then applying acid neutralising felt pads to the posts and cleaned terminals. Anti-corrosive spray can be used, and by coating each terminal, the job is done. If there is damage in old plastic guards, then new ones should be installed. However, the battery should be replaced if the terminals do not clamp tight or if the metal is being eaten by the corrosion. It is a goner if you see any green corrosion on the copper cable going into the moulded lead terminals.
Cheap lead battery terminals are sold by every auto shop. They do work, but there is only partial electrical contact and the clamp plate squash the cable flat. Pro-style cast copper compression terminals can be bought. A compression terminal is made from tinned copper and makes full 360-degree contact with the cable. In order to prevent corrosion, the whole connection needs to be sealed with red and black heat-shrinking tubing. Both the battery terminals should be disconnected. While you hacksaw the battery terminals from the cable, use a slip-joint plier to hold the terminals. Don’t saw it off while it’s still on the battery. Next, cut off about 1/2 inch of insulation from each cable. If the copper strands are green, clean them with a baking soda/water solution and a wire brush. Dry the cable with compressed air.
Slide the heat-shrinking tubing out of the way once you have finished applying it over the cable. Once done, insert the main cable and any smaller cables into the compression nut Screw on the battery terminal and tighten until snug. Then slide the heat-shrink tubing over the connection and use a heat gun to shrink it.
Remember, do not smoke and make it a point to wear eye protection while working on car batteries.