Natus Audiometer Algo 3 Replacement Battery 7.4V 2600mAh

Natus Algo 3 / Algo 3i — 7.4V Li-ion Replacement Battery (88889209)

This 7.4V, 2600mAh Li-ion battery replaces part number 88889209 in the Natus Algo 3 and Algo 3i portable newborn hearing screeners. These devices perform automated auditory brainstem response (AABR) testing in hospital nurseries and pediatric clinics. Keeping a charged spare on hand avoids gaps in screening throughput during shift changes or high-census periods.

• Algo 3 and Algo 3i compatibility: Both the Algo 3 and Algo 3i share the same battery bay, connector pinout, and BMS communication protocol — one part number covers both units. The voltage rail and cell configuration are identical across the two variants.
• Bench tested on actual hardware: We ran this cell through full charge cycles and monitored BMS handshake behavior. The protection circuit responded correctly to charge termination and load cutoff events without tripping false fault flags.
• First-use self-test protocol: After installing this battery, allow the Algo 3 to complete its full power-on self-test without interruption. The device BMS runs a verification routine at startup — cutting power during this sequence can trigger a persistent battery fault that won't clear until the next complete reboot.

Why the Algo 3 alarms low battery immediately after a confirmed full charge

The Algo 3 BMS calibrates its state-of-charge thresholds against the OEM cell's established charge curve. A new replacement cell has not yet completed a full learn cycle, so the BMS can misread the actual charge state and trip the low-battery alarm even when the cell is fully charged. This is not a fault with the battery — it resolves after one complete charge-to-discharge cycle. Run the battery down to automatic shutoff, then charge it fully before the device returns to clinical rotation. After that conditioning cycle, the BMS reads state-of-charge accurately.

Algo 3 shutting off mid-screening with no low battery warning

The Algo 3 applies a short, elevated load burst during AABR stimulus delivery. In the first ten cycles, a new Li-ion cell has higher internal resistance than a broken-in cell, which causes a momentary voltage sag under that load. If the sag crosses the BMS undervoltage cutoff threshold, the device shuts off without a warning — the event is too fast for the alarm to trigger. Measure resting voltage immediately after a shutdown; if it reads above 7.0V, the cell is not depleted and internal resistance is the cause. Complete five to ten full charge-discharge cycles to bring cell resistance down to normal operating range before relying on the device for uninterrupted screenings.