For the proper capacity, pay attention to the Cold Cranking Amp (CCA) number on the batter
The original shape must be maintained to achieve full contact between the post and clamp. Any time a battery is replaced, the clamps on the cable connections should be cleaned properly. Many a "battery" problem turns out to be a connection problem. The best way to prevent corrosion on a battery is to seal the connections. A good connection can be sealed with a spray protectorant or with a high-temperature electrical grease. With the spray it might be difficult to coat the underside of the connection. In this case use a small brush to complete the job. If grease is used as a sealer, it should be a type made for electrical connections. During the life of a battery, the connections often get hot. Ordinary grease can liquefy under these conditions. It can then run down inside the connection and insulate the post from the clamp. Again, this is not a visible problem.
SCR: We've seen people who often are using the emergency connector. Any problems with that?
Kimbrough: These are the connectors with a bolt-down clamp for the wire. When a corroded terminal fails, use one of these to get home. The biggest problem here is the lack of contact in the connection. The strap is steel and not as conductive as the all-lead connection. Also these connectors are more prone to corrosion. Far too much of the cable, which is copper, is exposed to the air. Moisture in the air, especially salty air, causes corrosion to form. Corrosion can even extend up inside the cable insulation and cause a hidden problem.
SCR: How bad is it for battery life to let the battery stand in an uncharged or dead state?
Kimbrough: All batteries self discharge. A battery will lose 3 to 5 percent of its charge per month just sitting on the shelf. If it sits too long, the battery life expectancy is reduced. When purchasing a battery, do so from a company which insures its batteries are fresh. One easy way to damage a battery is to discharge it and then to store it without it being recharged.