EV Efficiency

Background

The battery power delivered is given by

P_{battery} = V_{battery} I_{battery}

The delivered energy can be found by integrating (adding the area below) the power time series.

The mechanical power delivered is given by the product of the motor torque and the motor angular velocity.

P_{mechanical} = \tau_{motor} \omega_{motor}

The mechanical energy delivered can be found by integrating this power time series.

The distance traveled can be found by integrating the speed time series.

Preparation

• Is the efficacy we are estimating direct or indirect?
• What direct measurements do we need?
• Will these be single measurements or time-series?
• Will we use slopes, areas, or both?
• We’ll come up with a data file naming convention.

Data Collection

• We will set our vehicle (or prony brake demo) to log data
• We’ll plot the data as we collect

Analysis

• Use your choice of spreadsheet or scripting
• Compute and plot the distance time series
• Compute and plot the battery energy consumed time series
• Stretch: compute and plot the mechanical energy time series
• Compute and plot the average efficiency time series
• Compute and plot the instantaneous efficiency time series

Exercises

Proposed Plan

• Explain how you will calculate efficiency by describing the direct and indirect measurements you’ll make
• What predictions do you expect based on what you know about motors?

Data Collection

• Upload a photo of our data collection
• Upload a photo of your preliminary plots

EV Efficiency Report Document

• Turn in a PDF document with
  • Our analysis graphs
  • Brief descriptions of the graph data sources