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After more research, we've found that most EV manufacturers (including Tesla) only use passive balancing. This whitepaper from Li-Ion BMS is a good comparison between active and passive cell balancing. Notably, there is a difference between balancing and redistribution. The goal of balancing is to equalize SOCs, while the goal of redistribution is to equalize capacities. Generally, it seems like the cell balancing algorithm used has a greater impact than the type of balancing. In addition, we determined that our powertrain, solar array, and aerodynamics will have a far greater effect on performance.
Overall, it seems like the practical benefit between active and passive cell balancing is minimal for our situation, as we're planning on building a matched pack and will be charging for an extended period of time. Since we'll be charging whenever we're coasting and we're looking at 5kW chargers, we should have plenty of time to use a slower balancing cycle. If we're able to implement an SOC-based balancing algorithm, we'll be able to balance anytime we want instead of just at the top of the charge curve, reducing the required cell balance current further. This whitepaper on balancing current is interesting.
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