🔍 Key Concepts

• Difference between lead-acid and nickel-cadmium (Ni-Cd) batteries when judging state of charge • How specific gravity of electrolyte behaves (or doesn’t) in different battery chemistries • What measurements (voltage, current, electrolyte tests) actually change in a predictable way with state of charge for Ni-Cd wet cells

💭 Think About

• Ask yourself: in a nickel-cadmium battery, does the electrolyte density (specific gravity) change significantly as the battery charges and discharges, or does it stay nearly constant? • Consider which measurement gives a consistent, repeatable indication of how full the battery is, regardless of whether it is being charged or discharged. • Think about what each option is really telling you: level, voltage, specific gravity, or current. Which of these directly tracks how much energy is stored in a Ni-Cd battery?

✅ Before You Answer

• Verify what happens to electrolyte specific gravity in Ni-Cd batteries during charge and discharge compared to lead-acid batteries. • Check whether electrolyte level or current will necessarily correspond to how charged the battery is at any given time. • Confirm which parameter (voltage, current, level, or specific gravity) manufacturers recommend as the primary indicator of state of charge for nickel-cadmium wet cells.