Powering the Car: Lithium-Ion Batteries

Electrical System, Featured / Monday, December 3rd, 2018

We decided to make our car for the Solar Car Challenge’s Advanced Division, so we are allowed to use other batteries, such as Lithium-Ion Batteries, in our car instead of deep-cycle Lead-Acid batteries. Though it does make the design more complicated, this different battery technology has many benefits for our car. Due to the Lithium-Ion Batteries, our battery will be lighter in weight and smaller in size. These benefits do come at the cost of complication: we must be very careful with balancing our cells, we must assemble our battery pack of many cells, and we must be careful to work within the specifications of the batteries. Our 5 kWh battery pack is made up of 476 Panasonic Lithium-Ion 18650 Cells. We are running the pack in a 28 Series x 17 Parallel Configuration, giving us a nominal voltage of just over 100V, with the peak at just around 120V.

Jon Wick, an engineer on the team, spot-welding our large battery pack.

We started testing the lithium batteries by building a smaller pack. Our 13 Series x 2 Parallel Configuration was a great way to get used to spot welding and configuring a battery pack.

Our 13S 2P testing battery pack. This pack was used to learn about spot-welding, and battery pack configuration.
Wiring up our 13S 2P Battery Pack to a small MPPT for testing various solar cells.

We are now working on building our main pack. We used what we learned to choose the proper cells and determine the best configuration. We have spot welded all the cells and are in the process of wiring up our Battery Management System (BMS). In the process, we must be very careful and take safety precautions: the battery can be potentially dangerous.

Our main pack cells arrived! Here we are starting the assembly of the battery pack.
Assembling the main battery pack into our cell holders.

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