Bison Model 80 Medical Device Replacement Battery 12V 5000mAh

Bison Model 80 — 12V Ni-MH 5000mAh Replacement Battery

This is a 12V 5000mAh Ni-MH replacement battery for the Bison Model 80 medical device. It delivers 60Wh of capacity and matches the voltage and chemistry of the original cell. The connector and physical dimensions (310 x 65 x 33.3mm) align with the Model 80 battery bay.

• Bison Model 80 fit: The Model 80 uses a 12V Ni-MH cell with a specific BMS handshake tied to charge-curve recognition. Substituting Li-ion here would mismatch the charge IC — Ni-MH chemistry is not optional on this platform.
• Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on the bench. The BMS accepted the cell without fault flags after the first complete cycle, and voltage held steady through the load profile.
• Post-swap self-test requirement: After installing this battery, let the Model 80 complete its full power-on self-test without interruption. The BMS runs a verification sequence at startup — cutting power during that window registers a battery fault that persists until the next clean reboot.

Why the Model 80 alarms low battery immediately after a confirmed full charge

The Model 80's BMS compares the incoming cell's charge curve against a stored threshold profile calibrated for the original OEM cell. A new replacement cell hasn't yet built a recognised charge history, so the BMS can flag it as insufficient even at full voltage. This isn't a fault with the cell — it's the controller applying a conservative threshold to an unrecognised profile. One complete charge-discharge cycle gives the BMS enough data to stop triggering the alarm.

Model 80 not completing boot sequence after cell sat in storage

Ni-MH cells self-discharge in storage, and if this battery sat long enough, the resting voltage may have dropped below the Model 80's BMS recovery threshold. At that voltage, the controller blocks boot to protect the device rather than attempt to run on a depleted cell. Connect the device to the charger and leave it for a full uninterrupted charge cycle before attempting to power on. Once the cell recovers above the BMS minimum — typically around 10.8V for a 12V Ni-MH pack — the boot sequence completes normally.