Experiment 14 - Discharging Battery III

How does the internal resistor change, when the battery is almost completely exhausted? For this leave the circuit connected to a further 30 minutes. Disconnect the battery, give it a few minutes to "rest" and repeat the measurements.

At the battery you measure a voltage U₀ = 8.4 V.

The current through the load circuit has collapsed and is only I = 0.10 A. The battery is depleted significantly.

Hence the internal resistor has risen to the rather high value R_i = 74 Ω.

Measuring the voltage U0 of the almost depleted battery without a load circuit.

Measurement of the current I in a load circuit.

The internal resistance Ri is dependent on the state of charge of the battery and increases sharply when the battery is exhausted.

What practical implications does this have...?