ECE 2100 The Battery Project Dr Len Trombetta

ECE 2100 The Battery Project Dr. Len Trombetta 1

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). 2

Mechanics • Experiment: Work with your lab partner – 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…) 3

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 …) 4

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. 5

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. 6

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? 7

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. 8