Revisiting Our Batteries

Electrical System, Featured, General, Post of the Week / Thursday, May 30th, 2024

As the countdown towards race day continues, the team has been hard at work getting ready for testing the car. However, we are not just testing improved systems;we also have been making sure previous components are up to date with the Solar Car Challenge’s rules.

One key part of Sockeye is our main battery, which was built last year. Although we had tested our batteries and saw that they complied with the requirement of 5.25 kWh (kilowatt-hour) or less for the battery’s energy, we thought it would be beneficial to run a thorough battery test to verify those findings. They would also help us determine if we needed to build a new battery or if we could keep the current battery for our upcoming race in Texas.

Battery testing setup

The tests conducted on our LG MJ1 batteries consisted of ten cycles of charging a single battery cell to its maximum voltage, waiting five minutes, discharging to its lowest rated voltage, then waiting another five minutes. Our battery is made up of 450 of these cells, structured in a grid to create the battery pack. We tested ten different cells on an EBC-A20 battery tester, with the data gathered from those tests processed in a spreadsheet to compare discharge energies.

Graph created from a battery test

From the results of these tests, we found that the batteries still complied with the Solar Car Challenge’s rules as each cell never exceeded 11.67 kWh at the recommended 1C (one hour) discharge rate. This means that our battery pack is, if all 10 cycles across the 10 batteries was averaged, the pack energy would be lower than the 5.25kWh maximum at 5.18kWh.

Though there were minor differences in discharge energies across all ten cells, further analysis chalked it down to the slight temperature changes in the testing environment. Overall, it seems that the team will not have to replace the main battery after all.

While it may have seemed unnecessary, the analysis on our batteries was a crucial part of preparing for the race in Texas. With more testing to come we’ll further see the use of these measurements in strategic calculations as well to prepare the car for July.

2 Replies to “Revisiting Our Batteries”

  1. Really enjoy knowing how detailed your preparations are, and especially like that you included the chart! This is all very exciting!! Keep up this great work!

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