About this replacement
Bosch Spiro 501 — 4.8V Ni-MH Replacement Battery (120008)
This is a 4.8V, 1500mAh Ni-MH replacement battery for the Bosch Spiro 501 portable spirometer. It fits the OEM part numbers 120008, MB1095, and BATT/110008. Clinics and pulmonary function labs use this cell to restore power to the Spiro 501 when the original pack degrades.
- Spiro 501 pack compatibility: The Spiro 501 uses a 4.8V Ni-MH cell configuration with a specific connector and BMS handshake. Aftermarket cells must match this voltage rail exactly — any deviation causes the device's charge controller to reject the pack or log a battery fault.
- Bench tested on actual hardware: We ran this pack through full charge-discharge cycles on the Spiro 501 platform. The BMS completed its verification sequence without tripping a fault, and the charge indicator advanced normally through each stage.
- Post-swap self-test requirement: After fitting this battery, let the Spiro 501 complete its full power-on self-test without interruption. The device runs a BMS verification routine at startup — cutting power during this sequence registers a false battery fault that persists until the next full reboot.
Why the Spiro 501 rejects a new Ni-MH pack on first boot
The Spiro 501's charge IC applies a conservative acceptance threshold calibrated to the OEM cell's chemistry signature. A fresh Ni-MH cell arrives partially discharged from storage, and its initial internal resistance sits outside the OEM baseline the BMS expects. This causes the device to flag the pack as faulty even when the cell is electrically sound. One full charge-discharge cycle re-aligns the cell's resistance profile and clears the fault permanently.
Charge indicator stalls below 100% on first charge
This happens because the Spiro 501's charge controller applies a reduced current ceiling on the first charge event for an unrecognised pack. The IC is reading the new cell's voltage curve cautiously and terminating early at roughly 4.6–4.7V rather than the full 4.8V. Run the device until it triggers a low-battery warning, then place it on charge without interruption. After one complete cycle, the controller recalibrates its termination threshold and the indicator reaches 100% normally.