Question 6A270

When charging a storage cell, reversing the polarity has different effects depending on the battery chemistry. **For lead-acid cells (A):** Reversing polarity forces the plates to undergo chemical reactions opposite to their design, leading to gassing, heat, and severe damage to the plates and electrolyte (e.g., sulfation, irreversible plate degradation). This can significantly reduce capacity or destroy the cell. However, the statement "unless excessive" implies that a very brief, low-current reversal might not cause immediate, irreversible damage, but it is always detrimental and should be avoided. **For Edison cells (Nickel-Iron) (C):** Edison cells are renowned for their extreme robustness and tolerance to abuse. They can be overcharged, deeply discharged, and even reverse-charged without permanent damage. Their chemistry is much more forgiving to such events than lead-acid cells. Operating below 115 degrees Fahrenheit (approximately 46 degrees Celsius) is a condition for optimal performance and longevity for most battery types, but the core point is the Edison cell's inherent tolerance to reversed polarity. Therefore, both statements A (with its conditional "unless excessive") and C are considered true in the context of these battery types, making D the correct answer.