A system of batteries can provide intensity for a period of time without affecting tension in the poles. The capacity is the result of intensity by time. The manufacturer sets the capacity of the battery. New batteries have to be in use in order to achieve their maximum capacity.

As batteries age, the capacity diminishes. Therefore, the battery cannot provide the specified intensity for as long as before. In favorable conditions, the life expectancy of a battery can be up to 20 years, but there are many that last a lot less.

If current capacity is measured in a battery, it is possible to know if the system should be replaced or if it is in good condition. Knowing this information can save time and money..