While it’s common knowledge that a car’s battery can slowly go flat if unused for an extended period of time, it’s also possible for a brand new battery to lose charge as it sits on the shelf.

Probe, one of South Africa’s largest automotive battery importers, has offered an explanation to the phenomenon which is often mistaken for defective product.

“The chemistry in a battery requires reversible reactions that maintain a state of equilibrium as the current flows, meaning that the lead sulphate salts that form can be broken down,” says Probe’s head of quality control, Barnabas Gwarisa.

“This state of equilibria maintains the life of the battery. However, if a battery remains on the shelf for a long period of time or sits in an unused car, lead sulphate forms without being broken down.

“In the build-up of lead sulphate, a white salt layer develops inside the battery and settles around the battery’s active material, blocking the pores of the separators. This restricts the flow of electrons, and in the worst case scenario, cuts the circuit off completely as the current cannot flow,” explains Barnabas. “As more and more reaction surface becomes sulphated, there would be increased resistance in the battery, resulting in overheating.”

Sulphation is most common in lead acid batteries. However, Barnabas says that a sulphation problem can be easily identified. “An indication of sulphation is a whiteness in the eye of the battery. For a healthy battery fitted with a magic eye, this should be green.”

A green eye signifies a healthy, charged battery. A black eye indicates less than 65% charged. Barnabas adds a cautionary note, “Although a black battery eye might indicate that the battery is not fully charged, this doesn’t mean there is sulphation. You need to look for the whiteness around the eye, regardless of colour.”

The good news for consumers is that sulphation can be easily overcome. Barnabas says that when a vehicle is not being used for a period of time, the engine should nonetheless be started frequently. “Let the engine run for approximately 15 minutes to allow any sulphate salts that are being formed to break down. Do this once a week. Alternatively, it is useful to take a short drive, which helps keep everything in good working order.”