About this replacement
Stryker SP-1C / SP-2CX Series — 12V Ni-MH Replacement Battery (B11691)
This is a 12V 2500mAh Ni-MH replacement battery for the Stryker SP-1C and SP-2CX surgical power systems. It fits the handheld orthopedic drill and saw used in bone drilling, cutting, and shaping procedures. OEM part numbers B11691, B11449, and 5920-010-091 all cross-reference to this cell configuration.
- SP-1C and SP-2CX platform fit: Both instruments share the same 12V power rail, connector format, and BMS handshake protocol. The battery pack communicates cell status to the device controller on startup — voltage, temperature, and charge state must all pass before the instrument enables the motor drive circuit.
- Bench tested on actual hardware: We ran this pack through the SP-1C power-on self-test and confirmed the BMS handshake completed without fault codes. The cell cluster held voltage within spec under a simulated high-torque drill load across the first three charge-discharge cycles.
- Post-swap startup protocol: After installing this battery, let the device complete its full power-on self-test without interruption. The SP-1C runs a BMS verification sequence at boot — cutting power mid-cycle registers a false battery fault that persists until the next clean reboot from full charge.
Why the SP-1C alarms low battery with a freshly charged replacement installed
The SP-1C's charge IC applies a conservative acceptance threshold calibrated to an aged OEM cell. A new Ni-MH pack carries a slightly different internal resistance profile than a worn original, and the BMS can misread this as an undercharged state. The fix is one full charge-discharge cycle under normal instrument use — this allows the BMS to recalibrate its reference point against the new cell chemistry. After that cycle, the alarm clears and charge state reads correctly.
SP-1C won't power on after the replacement battery sat in storage
Ni-MH cells self-discharge at roughly 1–2% per day in storage. If the pack voltage drops below approximately 10.5V, the SP-1C's BMS treats it as a deeply discharged or faulty cell and blocks power-on entirely. Place the battery on a compatible Ni-MH charger and allow a full uninterrupted charge cycle before attempting to power the instrument. Once the pack returns above the BMS recovery threshold — typically around 11.0V — the SP-1C will complete its boot sequence normally.