1. ECE 2100
The Battery Project
Dr. Len Trombetta

2. The Goal
Measure the internal resistance of a AA battery as it is drained of energy.
Assume a model: an ideal voltage source in series with a resistance.
Plot or chart the internal resistance as a function of…(whatever variable you think is appropriate).

3. Mechanics Experiment: Work with your lab partner Lab Notebook
You will have the same data…
…but you will turn in separate reports
Lab Notebook
All data and notes are recorded in the lab notebook
Your lab notebook will be separate from your lab partner’s notebook
Report: A separate Formal Report will be submitted (discussed later…)

4. Materials and Tools Batteries
Two different types, two batteries of each type (total #batteries = 4)
Different brands
Different chemical types …
Equipment
You will need to purchase batteries and any other hardware you might want (battery holders, extra resistors …)

5. In Class
You will begin thinking about several aspects of the project in class…
What about the model…?
What methods will we use?
How should we display the data?
You will turn in a version of your Methods section after making some preliminary measurements.

6. Preliminary Measurements
Purchase batteries (and anything else you might want).
Start thinking about measurement methods. Take a few measurements in class to see what the parameters are.
Dr. T. will visit your team 23 Feb and grade your preliminary measurements portion.

7. Technical Considerations
You should be considering several technical issues as you set up your experiment. We will be looking for these things when we grade your papers.
Power dissipation in load resistors: have you considered this?
Effect of meter resistance: Is there any effect? How do you know?
Is vbatt constant as the battery drains (refer to the model shown earlier). How do you know? Did you measure it?
Plotting Rint as a function of …? How will you interpret the data? What sort of plots or charts will you show to illustrate the changing internal resistance?

8. Error
Think about error in your experiment, and be sure to include a discussion of it. You can put this in either the Results or the Discussion section.
What were the principal sources of error? Was it the multimeter, or something else?
What would you estimate is the error in your resistance measurements? Less than one percent? More than that? How much more?
How might you correct for that error.