Senior/Staff Firmware Engineer - BMS

1X Technologies AS•San Carlos, CA

About The Position

We are looking for a cross-functional Firmware / Embedded Engineer to develop and maintain the battery management firmware for a production humanoid robot. In this role, you will own the firmware that monitors, protects, and manages a high-energy lithium-ion battery pack operating under demanding and highly dynamic load conditions. You will work closely with hardware architects, electrical engineers, systems engineers, and test engineers to ensure firmware reliably bridges hardware capabilities and higher-level system requirements across prototype and production platforms. The battery system in a humanoid robot operates unlike most conventional applications. Load transients are severe and unpredictable — peak currents can cause significant bus voltage sag within milliseconds as actuators respond to real-time control policies. The pack must sustain continuous cycling in uncontrolled thermal environments while maintaining cell-level safety and accurate state estimation. There are no established BMS reference designs for this load profile. The ideal candidate reasons from electrochemistry and circuit fundamentals, builds reliable firmware for safety-critical systems, and is comfortable developing novel solutions where existing vendor toolchains and application notes fall short.

Requirements

Bachelor’s or Master’s degree in Electrical Engineering, Computer Engineering, or a related field
7+ years of industry experience with embedded systems and real-time firmware development
Proficiency in C and C++ for embedded targets
Production BMS firmware experience — the candidate has developed or substantially modified battery management firmware for a multi-cell lithium-ion or lithium-polymer pack in a shipped product. Experience should include cell monitoring, protection logic, and state estimation, not solely integration of a vendor BMS IC evaluation kit.
Electrochemical fundamentals — working understanding of lithium-ion cell behavior: capacity vs. discharge rate, impedance characteristics under temperature and aging, thermal runaway mechanisms, and how these translate into firmware protection thresholds and estimation algorithms
High-current / high-transient systems — experience with battery packs that supply dynamic loads with significant peak-to-average current ratios, where bus voltage management and transient response are firmware-level concerns
Embedded bus fluency — hands-on CAN/CANopen implementation plus additional embedded interfaces (SPI, I²C, UART) for communication with analog front-end ICs, fuel gauge ICs, and peripheral monitoring devices
Hardware debug at the firmware boundary — experience using oscilloscopes, logic analyzers, and current probes to diagnose problems that span firmware behavior, sense circuit accuracy, and protection circuit response
Schematic literacy — ability to read analog front-end circuits, current sense topologies (shunt, Hall-effect, fluxgate), cell balancing circuits, and protection FET gate drive without requiring hardware engineering interpretation
Comfortable debugging firmware on real hardware using standard lab tools
Ability to collaborate closely across hardware, systems, and software teams

Nice To Haves

First-principles problem solving — a track record of approaching unfamiliar problems by building understanding from fundamentals rather than relying on vendor application notes or established patterns. The BMS load profile in a humanoid robot does not match conventional EV, power tool, or stationary storage assumptions.
Safety-critical battery systems — experience with BMS firmware where protection failures have physical consequences (thermal runaway, fire, toxic gas release). Familiarity with standards such as IEC 62619, UL 2580, UN 38.3, or IEC 62133 and how they translate into firmware requirements.
EV or high-performance battery packs — experience at automotive OEMs, tier-1 battery suppliers, or EV startups where pack-level firmware must manage hundreds of amperes with cell-level granularity under thermal and mechanical stress
Power tool or robotics battery systems — experience with compact, high-discharge- rate packs where weight, volume, and thermal constraints are as demanding as electrical performance
SOC/SOH algorithm development — implementation of model-based estimation (equivalent circuit models, extended Kalman filters, or similar) beyond simple coulomb counting, validated against real cell aging data
Power system integration — experience where the BMS firmware must coordinate with DC-DC converters, pre-charge circuits, contactors, and system-level power sequencing
EMC awareness — experience with BMS subsystems that have contributed to or been affected by conducted or radiated emissions, and understanding of how firmware behavior (switching frequency, measurement timing) interacts with EMC performance
Experience contributing to hardware architecture or system-level design decisions
Familiarity with real-time operating systems (FreeRTOS, SafeRTOS, or similar)
Experience supporting hardware through prototype and production phases

Responsibilities

Develop and maintain BMS firmware including cell voltage monitoring, current measurement, temperature sensing, and protection enforcement across a multi-series lithium-ion pack
Implement state-of-charge (SOC) and state-of-health (SOH) estimation algorithms that remain accurate under high-rate transient loads, temperature variation, and cell aging
Architect cell balancing firmware (passive and/or active) that manages cell-to-cell divergence during both operation and charging, accounting for the wide SOC excursions typical of this application
Responsible for the testing, validation, and verification of initial firmware releases to ensure functionality, reliability, and performance requirements are met
Implement pack-level protection logic: overcurrent, overvoltage, undervoltage, overtemperature, and short-circuit detection with deterministic response times and safe- state transitions
Design brownout prediction and mitigation firmware — characterize and manage bus voltage sag under peak actuator loading to prevent cascading subsystem failures
Develop CAN/CANopen interface firmware for real-time reporting of pack state to the central controller, supporting both cyclic status data and diagnostic/configuration messaging
Collaborate with hardware architects to define BMS hardware requirements, sense circuit topology, and protection coordination between firmware and hardware safety mechanisms
Implement pre-charge sequencing, power-on/power-off state machines, and coordination with the system-level power distribution architecture
Develop production test hooks and end-of-line validation routines for battery pack acceptance, including cell matching verification and impedance measurement
Document firmware architecture, interfaces, and assumptions; improve code structure, readability, and maintainability