Oral-B 10000 Replacement Battery 3.7V 800mAh Li-ion

Oral-B 10000 / 3765 / 3766 / 3767 Series — 3.7V Li-ion Replacement Battery

This 3.7V 800mAh Li-ion cell replaces the internal battery in the Oral-B 10000, 3765, 3766, 3767, and compatible series electric toothbrushes. It fits the oscillating brush mechanism that drives the cleaning cycle. Capacity comes directly from product specifications — 800mAh (2.96Wh).

• Cross-model fit on the 10000 platform: The 10000, 3765, 3766, and 3767 share the same internal cell form factor, voltage rail, and BMS handshake protocol — the same 50.20 × 14.20 × 14.20mm cell runs across all of them without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 10000 platform. The BMS accepted the cell without triggering a protection fault, and the brush motor reached full oscillation speed within the first charge cycle.
• Charging port moisture check: Dry the charging port completely before docking — water bridging the charging contacts trips the BMS protection circuit. The toothbrush reports this as a dead battery, not a charging fault, so the root cause gets missed.

Capacity fade from daily partial charging on the Oral-B 10000

Most users dock the 10000 after every use rather than letting it fully discharge. Li-ion cells shallow-cycled this way develop voltage drift over time — the BMS recalibrates its state-of-charge estimate against a narrower actual capacity window. The indicator reads full but the cell can no longer deliver current at full brush speed for a full session. Replacing the cell resets this drift entirely, since the new cell has no prior cycle history to skew the BMS estimate.

Brush motor speed dropping before the indicator reaches empty

When the internal cell ages, its internal resistance rises. Under the motor's load the cell voltage sags below what the drive circuit needs before the BMS technically hits cutoff. The result is noticeable speed loss mid-session while the indicator still shows charge remaining. This is a voltage-sag fault under load, not a capacity readout error. Fitting a fresh cell brings the voltage under motor load back above 3.5V where the drive circuit maintains full oscillation speed.