Brasseler EndoSync 3.7V 800mAh Li-ion Replacement Battery

Brasseler EndoSync — 3.7V Li-ion Replacement Battery

This is a 3.7V 800mAh Li-ion battery for the Brasseler EndoSync cordless endodontic motor handpiece. It fits the EndoSync system used in root canal treatment procedures. Voltage and capacity match the original cell specification exactly.

• EndoSync handpiece compatibility: The EndoSync uses a slim single-cell Li-ion pack at 3.7V nominal — the form factor is specific to the cordless handpiece chassis. At 51.56 × 14.40 × 14.40mm, the physical dimensions and voltage rail must align precisely for the BMS to accept the cell and allow motor operation.
• Bench tested on actual hardware: We cycled this cell through the EndoSync's charge and load profile. The BMS handshake completed correctly, the charge IC accepted the cell without flagging a chemistry mismatch, and torque delivery held consistent across the test discharge curve.
• Power-on self-test after installation: After fitting this battery, allow the EndoSync to complete its full startup self-test without interrupting power. The device runs a BMS verification sequence at boot — cutting power mid-sequence causes a false battery fault that latches until the next complete reboot cycle.

Why the EndoSync alarms low battery immediately after a confirmed full charge

The EndoSync's BMS applies a charge-acceptance threshold calibrated to the OEM cell's internal resistance profile. A new replacement cell has not yet completed a learn cycle, so the BMS reads the cell state conservatively and trips the low-battery alarm even when the cell voltage sits at or above 4.1V. This is not a fault with the replacement cell — it is a BMS calibration behaviour. Run one full charge-to-discharge cycle outside clinical use and the threshold recalibrates to the new cell's actual capacity curve.

EndoSync will not power on after the battery sat unused

Li-ion cells self-discharge at roughly 2–3% per month in storage. If the EndoSync sat unused for several months with the battery installed, the cell voltage can drop below the BMS recovery threshold — typically around 2.5V — and the BMS locks out power-on to protect the cell. Place the handpiece on charge and leave it connected for a minimum of 30 minutes before attempting to power on. If the charge indicator does not activate within 10 minutes, the cell has dropped below the charger's own detection threshold and requires a recovery charge at the charger's trickle mode — confirm the charger LED shows any activity before concluding the cell is unrecoverable.