The Roadster’s Battery Safety Module (BSM) is the pack-level safety and control brain inside the ESS. It monitors high-voltage pack status (voltages, temperatures, isolation, and fault states), controls the main HV contactors and pre-charge, supervises the high-voltage interlock loop (HVIL), and communicates pack health to the VMS so the car can enter “ready” and charge safely.
The BSM is a custom Tesla design specific to the Roadster ESS and is no longer manufactured. It resides on an electronics board buried deep inside the ~1,000-lb main battery pack, surrounded by battery sheets, contactors, service plug hardware, and coolant plumbing. Access requires a battery pack pull and disassembly, which makes proactive service most practical when the ESS is already open for sheet work or upgrades.
With the global Roadster fleet now well past a decade in service, these boards commonly suffer from aging analog front-end components, drift in voltage and isolation sensing, heat-stressed solder joints, and occasional moisture or corrosion loading from years of thermal cycling. Because new assemblies are NLA and donor boards are the same age as the cars, a properly engineered rebuild is the only practical long-term solution.
We have reverse-engineered the Tesla Roadster BSM and provide full board-level repair and upgrade services. Our process addresses known aging and stress points rather than simply “repairing what failed.” Typical work includes:
Boards are reassembled with long-life components and improved practices to reduce future thermal and electrical stress, supporting long-term Roadster fleet reliability.
| Applies to | Tesla Roadster 1.5 & 2.x — Battery Safety Module (BSM) boards inside the ESS |
| Function | Pack-level safety controller: monitors high-voltage pack state, isolation and faults; controls main contactors and pre-charge; supervises HVIL; reports to the VMS so the car can drive and charge safely |
| Known issues | Aging analog/sensing components, drift in measurement channels, heat-stressed joints, occasional corrosion/contamination, and NLA status for complete assemblies |
| Service | Reverse-engineered board-level rebuild with refreshed sensing components, driver circuits, solder-joint rework, cleaning, and full functional testing on dedicated harnesses |
| Access | BSM is buried inside the ~1,000-lb ESS battery; requires battery pack removal and internal ESS disassembly for service |
This service is typically performed as part of an in-shop ESS teardown/rebuild where we can safely remove and reinstall the BSM board. In select cases, a ship-in BSM sub-assembly may be coordinated when the pack has already been opened by qualified personnel. Turnaround time depends on board condition and any associated ESS work. We can coordinate BSM rebuild alongside APS/DC-DC repair and battery-sheet upgrades to minimize duplicate labor and downtime.
With ~2,000 Roadsters now beyond a decade in service, proactively rebuilding the BSM during ESS work helps preserve safe pack operation, reduce nuisance isolation and HVIL faults, and avoid the frustration of a Roadster that will not go “ready” despite a healthy battery.
Questions or Roadster tech support:
623-433-8500
Maintenance Tip:
To reduce stress on ESS electronics such as the BSM, keep your Roadster in an environmentally controlled environment when parked.
