Rivian R1S/T Battery BMS Pinouts solved!_

# [Wiki Update] Reverse-Engineered Rivian 864-Cell Module BMS Pinouts & Connectors Hey everyone, I’ve just finished mapping out the internal cell tap routing and thermal sensor connectors for the Rivian 864-cell battery modules, and the complete documentation is now live on the wiki. We initially thought these operated as parallel strings, but after verifying tap voltages across multiple packs and referencing teardowns, we've confirmed the entire 864-cell module is a **single continuous 12S72P series string** (47.6V nominal). Because Rivian uses staggered "tuning fork" busbars that bridge the left and right cell groups together at every series step, the BMS wiring is split into two distinct tiers: * **The Upper Layer (White Connector):** Monitors the bottom half of the series string (Cells 1-6, or 0V to 23.7V) with a perfectly symmetrical left/right redundant pinout. * **The Lower Layer (Black Connector):** Continues the string (Cells 7-12, or 23.7V to 47.6V). Because of how the busbars bridge the cells, this side has an asymmetrical pinout where several left-side pins are completely floating (No Connection). Crucially, we successfully tracked down all the exact OEM connector part numbers and their mating PCB headers so we don't have to splice into the fragile factory Flexible Flat Cables (FFC). **What's Documented:** * Upper Layer Voltage Taps (TE Connectivity NanoMQS Code B) + 1-6S Pinout * Lower Layer Voltage Taps (TE Connectivity NanoMQS Code A) + 7-12S Pinout (including floating logic ground pins) * Module Temperature Sensors (Molex Mini50) **Next Steps / The Goal:** Instead of running long, centralized analog cables that act as EMI antennas and create serious safety risks, the plan is to design a custom, open-source distributed BMS slave board. This PCB will mount directly onto the Rivian module to handle local cell monitoring and passive balancing, and then communicate back to the main OpenVCU controller via a robust digital link (like CAN or isoSPI). **Read the full documentation on the wiki:** [Rivian 864-Cell Battery Module: BMS Interface](https://openvcu.org/wiki/article/rivian-864-cell-battery-module-bms-interface) Has anyone else started laying out a footprint for these TE NanoMQS right-angle headers? What cell-monitoring ICs (TI, Analog Devices, etc.) are you favoring for 12S slave boards right now? "An expert is a man who has made all the mistakes, which can be made, in a very narrow field." -Niels Bohr