Nihon Kohden NKB-101 BSM-4000 Replacement Battery 12V 3000mAh

Nihon Kohden BSM-4000 / TEC 825 Series — 12V Ni-MH Replacement Battery (NKB-101)

This 12V 3000mAh (36Wh) Ni-MH battery replaces the NKB-101 and compatible part numbers in the Nihon Kohden BSM-4000 and BSM-5100 bedside patient monitors, as well as the TEC 825 and TEC8250 defibrillators. It restores portable operation for patient transport and covers against mains interruption. Dimensions are 141.55 × 97.60 × 29.86mm — match these before installation in your unit.

• Cross-platform fit — monitors and defibrillators: The BSM-4000, BSM-5100, TEC 825, and TEC8250 share a common 12V battery bay and connector spec. The BMS handshake protocol is consistent across this Nihon Kohden platform, which is why one cell covers both monitoring and defibrillation hardware.
• Bench tested on actual hardware: We cycled this cell through charge and load discharge on the BSM-4000 platform. The BMS accepted the cell without fault on the first full charge cycle. Voltage held steady at 12V nominal under the monitor's continuous ECG and SpO₂ load profile.
• Post-swap self-test protocol: After fitting this battery, allow the BSM-4000 to complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during this window logs a false battery fault that persists until the next complete reboot cycle.

Why the BSM-4000 alarms low battery immediately after a confirmed full charge

The BSM-4000's charge IC applies a conservative acceptance threshold calibrated to a conditioned OEM cell. A new Ni-MH cell that has not completed its first full charge-discharge cycle presents a slightly different internal resistance profile than a broken-in cell. The monitor's BMS reads this as insufficient capacity and triggers the low-battery alarm even when the cell is at full state of charge. Run one complete charge-to-discharge cycle before treating any alarm as a fault. After that cycle, the BMS recalibrates its threshold to the new cell's actual resistance curve.

BSM-4000 will not power on after battery sat in storage

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A cell stored for several months can drop below the BSM-4000's BMS recovery threshold — typically around 10V on a 12V pack — and the monitor will refuse to boot rather than risk a mid-session cutoff. Connect the battery to the monitor on mains power and leave it on charge for a full uninterrupted cycle. If the charge indicator does not advance after 30 minutes, the cell voltage may be below the charger's kick-start floor; some charge ICs require the pack to be at or above 10.5V before the charge sequence initiates.