Explanation: To determine the voltage needed for charging, we must consider the battery's total open-circuit voltage and its total internal resistance, using Ohm's Law. First, calculate the total characteristics for the 3-cell battery: * Total open-circuit voltage = 3 cells * 1.8 V/cell = 5.4 V * Total internal resistance = 3 cells * 0.1 ohm/cell = 0.3 ohm For charging, the external voltage must overcome the battery's open-circuit voltage AND create a voltage drop across the internal resistance to drive the desired current. Using Ohm's Law, the voltage drop across the internal resistance (V_internal_drop) is Current (I) * Total Internal Resistance (R_internal). V_internal_drop = 10 A * 0.3 ohms = 3 V The required charging voltage is the sum of the battery's open-circuit voltage and the voltage drop across its internal resistance: Charging Voltage = Total Open-Circuit Voltage + V_internal_drop Charging Voltage = 5.4 V + 3 V = 8.4 V This ensures an initial 10 A current flows against the battery's natural voltage and through its internal resistance. Therefore, 8.4 V is needed.