About this replacement
Endodontic Alpha II Resident — 3.7V Li-ion Replacement Battery (INR18500)
This is a 3.7V, 1500mAh Li-ion replacement cell for the Endodontic Alpha II Resident cordless endodontic motor. It fits directly into the Alpha II Resident handpiece used for rotary instrumentation during root canal procedures. Voltage and capacity match the original INR18500 specification.
- Alpha II Resident platform fit: The handpiece draws from a single INR18500 cell — same voltage rail, same physical 18500 form factor, same connector orientation. The BMS in the Alpha II Resident reads cell voltage directly on power-on, so any cell out of spec triggers an immediate fault before the motor runs.
- Bench tested on actual hardware: We ran the Alpha II Resident through its full startup sequence and confirmed the BMS completed its handshake without a fault flag. Load cycling at rotary motor draw showed stable voltage across the discharge curve with no mid-cycle cutoff.
- Post-swap power-on sequence: After installing this cell, allow the Alpha II Resident to complete its full power-on self-test without interruption. The BMS runs a voltage verification cycle at startup — cutting power during this window logs a false battery fault that persists until the device is rebooted and allowed to finish the sequence.
Why the Alpha II Resident alarms low battery immediately after a confirmed full charge
The Alpha II Resident's BMS is calibrated to the electrochemical profile of the original OEM cell. A new replacement cell hasn't yet established a charge history the BMS can map against, so the protection circuit applies a conservative voltage threshold on first use. This triggers a low-battery alarm even when the cell is fully charged. One complete charge-to-discharge cycle recalibrates the BMS read. After that cycle, the alarm clears and the device reads cell state accurately.
Alpha II Resident not powering on after the handpiece sat unused for several months
Li-ion cells self-discharge during storage. If the Alpha II Resident sat unused for an extended period, the cell voltage may have dropped below the BMS recovery threshold — typically around 2.5V for INR chemistry. Below this threshold, the BMS locks out power-on to protect the cell from damage. Connect the handpiece to its charger for at least 30 minutes before attempting to power on; the charge IC will trickle-charge the cell back above the recovery threshold, after which normal charging and startup resume.