Which of the following statements is not an advantage of an alkaline accumulator?

Analyze the question: We need the statement that is NOT an advantage of an alkaline accumulator (e.g. Nickel-Iron / Edison cell or Nickel-Cadmium cell). It's an "EXCEPT"-type question.

Concept: Alkaline vs lead-acid accumulators

Alkaline accumulators (Ni-Fe or Ni-Cd) use potassium hydroxide (KOH) as the electrolyte.

Advantages over lead-acid:

• Longer life (more durable and robust)
• Can be recharged many times
• Electrolyte does not deteriorate, so it needs little attention, and it is not corrosive like sulphuric acid
• Can be left uncharged or discharged for long periods without damage

Disadvantages:

• Higher internal resistance, so it delivers lower current and has a lower e.m.f. per cell (about 1.2 V vs about 2 V for lead-acid)
• More expensive
• Less efficient

Checking each option:

• A. The electrolyte does not need attention. This is an advantage, because the KOH electrolyte does not change chemically during use.
• B. It can be recharged. This is an advantage, since it is a secondary cell.
• C. It has low internal resistance. This is false. Alkaline accumulators have a high internal resistance, whereas lead-acid accumulators have a low one. So this is NOT an advantage.
• D. It has a much longer life than lead-acid accumulator. This is an advantage.

Tip: Remember that lead-acid cells are good at delivering large currents (e.g. starting a car) because of their low internal resistance. Alkaline cells win on durability and low maintenance, but lose on internal resistance and cost.