Trip Stats

Summary

This was the day when we almost blew our only copies of the BMS AFE boards. You can read details in the post-mortem, but essentially, because the voltage taps and thermistor connectors weren't keyed, we mistakenly plugged the voltage taps into the thermistor inputs, and damaged the MUX. Thankfully, replacing the MUX seemed to allow us to get back in business (albeit with no thermistor readings), but it took us out of commission for a good 3 hours.

Other than that, everything went pretty smoothly, and we breezed through to the stage stop. We stopped 2-3 times for the usual Motor Controllers overheating, and then another time for a 10 minute driver swap (and ice cream) break.

There was a minor issue where our Telemetry system was indicating that there was about a 250 mV offset at lower voltages, that eventually became a 400 mV offset between our lowest and average cell voltage in the pack as the pack voltage dropped, which seemed to be indicative of a board issue that we would debug later in the evening at the campground. The people in the convoy collectively deemed this as a non-issue in terms of our pack capacity, as it seemed to just be a linear offset and not indicative of the actual cell capacity, so we wouldn't experience that sharp dropoff when we dropped below 3.5 V. The voltage seemed to be being shared between AUX input 15 and 16, where taking the average of the two would equal the average voltage of the rest of the pack. We basically treated it as a linear offset for when our pack would undervoltage fault, which we were confident we wouldn't hit, seeing as we had more than enough projected capacity to finish the stage.

Later that night at the campground, we ate dinner and had a team meeting about finances. Minnesota was also camping at the same campsite, and a few of us headed over to chat with them and see how they were holding up. They said that they'd finally diagnosed their electrical short issues, and so said that we'd see each other at the finish line tomorrow before heading back to where we left the solar car. We diagnosed the issue we were seeing with AUX input 15/16 before setting the car up for charging. It turns out that there was a cold solder joint on the fuses, and touching that up fixed our voltage readings on those cell inputs

Results