Overview

To meet our metric that  “the buoy’s battery charge will lose less than 10% over 1 hour,” we calculated an estimate of the Arduino’s power consumption. Initially, we were planning to measure the current draw of the Arduino with a multi-meter when it was not sending power to the motor. Then, we were planning on extrapolating that current draw over an hour to calculate the power consumption. Unfortunately, we found that a battery’s charge is not linear, as seen in the graphic below. The graphic shown is not the data for the battery that we are using; the data is not available for this battery. With this discovery, we determined that this test is not possible to perform. However, we were able to perform some theoretical calculations.

​

​

​

​

​

​

​

​

​

​

​

​

​

Analysis

With a fully-charged battery, the voltage measures 9.6 V. We measured 0.195 A of current draw when the battery was plugged in to the active Arduino. We measured the current when the motor was not being energized by the Arduino. The battery is rated for 3000 mAh and 8.4 V. We used an online converter to verify that the instantaneously-measured current (0.195 A) over one hour is equivalent to 195 mAh. By calculating the relationship of  the Arduino current draw and the battery rating (195mAh/3000mAh = .065 = 6.5%), we were able to confirm that the power consumption over an hour was less than 10%, which satisfies our metric and passes the test.