About this replacement
Criticare LT Plus / 507NJC BP / Poet LT — 7.2V Ni-MH Replacement Battery (80512B001)
This is a 7.2V, 2500mAh Ni-MH replacement battery for the Criticare LT Plus patient monitor and compatible portable vital signs monitors including the 507NJC BP and Poet LT Pulse Oximeter. OEM part numbers covered: 80512B001, BATT/110280, and 602-14. Use the capacity figure from the product data — 2500mAh (18Wh) — when logging this into your equipment maintenance records.
- Shared platform across LT series monitors: The LT Plus, 507NJC BP, Poet LT, and 602-14 variants share the same 7.2V Ni-MH battery rail, connector pinout, and BMS handshake protocol — which is why a single part number spans all four. Voltage tolerance is tight on these monitors; deviating from 7.2V nominal causes the charge IC to reject the pack outright.
- Bench tested on actual hardware: We cycled this pack through the LT Plus power-on sequence and monitored BMS communication. The cell accepted the charge IC handshake cleanly after one full charge-discharge cycle. Capacity settled at rated output by cycle two.
- Post-installation self-test protocol: After fitting this battery, let the monitor complete its full power-on self-test without interrupting it. The LT Plus runs a BMS verification pass at startup — cutting power mid-sequence flags a false battery fault that sticks until the next clean full reboot.
Why the LT Plus triggers a low-battery alarm immediately after a confirmed full charge
This happens because the BMS threshold for the low-battery alarm is calibrated against the OEM cell's internal resistance profile. A fresh replacement cell has a slightly different resistance curve in its first few cycles, and the BMS reads this as a state-of-charge shortfall even when the pack is fully charged. The fix is straightforward: run one complete charge-discharge cycle before returning the unit to clinical rotation. After that cycle, the BMS learns the new cell's resistance baseline and the alarm clears. Confirm full charge by checking the charge indicator holds steady at 100% through a second uninterrupted charge session.
LT Plus will not power on after battery sat in storage
Ni-MH cells self-discharge at roughly 1–2% per day in storage. A pack that has sat unused for several weeks can drop below the BMS's minimum recovery threshold — typically around 6.0V for a 7.2V Ni-MH pack — causing the monitor to show no response at all when the power button is pressed. Place the battery on charge using the monitor's own charging circuit and leave it for a full uninterrupted charge cycle before attempting to power on. If the charge indicator does not light within 15 minutes, the cell voltage has dropped below the charger's detection floor — try a compatible external Ni-MH charger set to 7.2V to initiate recovery, then transfer back to the device.