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Linear Tech released the LTC6813-1, which is likely the same chip that is used in the Tesla Model 3 (if not very similar). This provides a bidirectional isoSPI interface, allowing for a break in the isoSPI chain in one direction. The idea would be that the driver would alternate the direction of reads for every read, such that if one pair of lines broke, it would still be possible to receive data, albeit at half the rate.

Redundant Sensors/Quorum

In the name of safety (and cool things we can build), one of the things that would be interesting is setting up redundant sense lines for the battery pack.

Depending on what failure methods we are protecting against, we could choose to do different things. We could just aim for N-level redundancy on sensor inputs, which would mean running N separate sets of voltage taps and thermistors to another microcontroller, and then ensuring that the variance between the two is within a specified threshold. I guess it's not truly N-level redundancy, since you don't have a way of determining which sensor reading is the accurate one—this just allows you to detect that there is a bad reading.

If we really wanted to be ambitious and do quorum-based voting, we would need (n / 2) + 1 members in order to be tolerant of n failures. In the past, we have run into issues with AFE sense reading incorrectly (due to bad solder joints), so performing consensus via a quorum of (n / 2) + 1 members would help mitigate that.