When constructed as above described and used in a local circuit, the Daniell battery will continue in action about ten or fifteen days without attention, the time depending upon the size of the wire in the magnet and the amount of daily service. The sulphate of copper solution should be kept of good strength, otherwise the upper portion becomes weak and an extra current is set up within the battery, which tends to eat away and destroy the copper plate without any useful effect. The copper deposit upon the zincs is valuable, and should be preserved. Every two or three months the coppers ought to be taken out and the deposit upon their surface removed, which may be done two or three times. When they become too much encrusted to afford room for the porous cups they must be replaced by new ones.
Porous cups ought to be renewed whenever they become too much encrusted with copper.
If cracked they should be changed at once, otherwise a great waste of material will ensue. The crystals which form around the edge of the outer jar require to be occasionally wiped off with a damp cloth, or they will eventually run down the outside and form a connection between the jars, giving rise to a great consumption of material without corresponding benefit. In order that the current may act with its full force, it is necessary to keep the clamps and connections of the battery clean and bright, and free from rust or dirt. As chemical action is promoted by heat, the battery will act more vigorously if kept in a warm place. This battery is sometimes used for main circuits, but in that case it is preferable to arrange it differently by placing the zincs outside and the copper within the porous cell, as in fig.