Measuring Internal Resistance of Batteries

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Contributors: Shawn Hymel
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Take Voltage Measurements

Measurement Sheet

Create a table for recording voltages:

Voltages 330 Ω Load 10k Ω Load Open Circuit
Lemon Battery

330 Ω Load

Touch the negative probe (black wire in the picture) to the anode (nail/screw) on the battery, and touch the positive probe (red wire in the picture) to the cathode (penny) terminal on the battery. Record the voltage under "330 Ω Load."

Loaded voltage of the lemon battery

NOTE: If you are using a multimeter for this exercise, we recommend using something like alligator test leads to hold the resistor across the electrodes of the battery.

10k Ω Load

Replace the 330 Ω resistor with a 10k Ω. Repeat the process to measure the voltage across the battery. Record the voltage under "10k Ω Load."

Open Circuit Voltage

Remove the resistor from the breadboard and take another measurement. Record the voltage under "Open Circuit."

Open circuit voltage of the lemon battery