RedTop

For normal engine starting where an alternator immediately monitors the state of charge and provides energy to the battery whenever it is needed.

This would describe most stock vehicles, including: automotive and RV underhood starting, heavy equipment where starting is the primary function, and diesel vehicles without aftermarket electronics.

YellowTop

Use this when electrical loads are higher than average, or when the discharge cycle is more than typical engine starting, such as vehicles with multiple electronic accessories and vehicles without alternators. This can also include vehicles with a lot of factory electronics such as power sliding doors and a DVD player. Examples also include: racing vehicles without a charging system, dedicated drag racers, diesel powered vehicles with aftermarket electronics, and vehicles with inverters, winches, or other accessories.

BlueTop

The BlueTop starting battery (dark gray case) is to be used when a dedicated starting battery is required and it should never be used for cycling duty. Use a BlueTop starting battery for marine applications and RVs when the battery's only function is engine starting.

The dual purpose BlueTop (light gray case) can be used for both starting and deep cycling -- it is a true deep cycle battery with extremely high cranking power. Uses include: trolling motors, marine applications with heavy electrical accessories, and RVs.