Visually inspect the battery plates with a flashlight. Check the negative plates and straps for a pinkish deposit during all battery inspections.
According to Exide and C&D, the copper does not remain isolated from electrolyte attack throughout the design life of the cell if improper alignment or casting occurred at the time of manufacture. For example, gases caught in the lead coating during the casting and freezing involved in the manufacturing process may later develop into perforations that become a path between the battery electrolyte and the copper inserts.
The battery electrolyte attacks all copper and cupric alloys, causing copper to deposit on the negative plates of the affected cell. The first typical indication of copper contamination is the discoloration, a pinkish-red color, of the negative plates and straps, and as the contamination progresses, the discoloration works its way down the negative plates. This condition can quickly lead to loss of battery capacity and serious deterioration.
Notice from the pictures below that cell number 17 has a pinkish-red color on the negative straps and plate. Cell number 19 (above) is the normal grayish-white color for the negative straps and plates.