Oral-B Triumph 4000 Replacement Battery 1.2V 2000mAh

Oral-B Triumph 4000 — 1.2V Ni-MH Replacement Battery (3761)

This is a 1.2V, 2000mAh Ni-MH cell for the Oral-B Triumph 4000 electric toothbrush. It replaces OEM part numbers 3761, 3762, and 3745. If your toothbrush no longer holds a charge or the motor runs slower than it used to, this cell is the direct fix.

• Triumph 4000 compatibility: The Triumph 4000 uses a sealed handle with an inductive charging base. This cell matches the voltage rail and physical footprint the handle expects — 43.15 x 16.95 x 16.70mm — so the cell seats correctly against the motor and charge contacts without modification.
• Bench tested on actual hardware: We cycled this cell through the Triumph 4000's inductive base and confirmed full charge acceptance, stable motor output, and correct BMS cutoff behaviour at low voltage. No false-low readings on the charge indicator during testing.
• Dock charging discipline: Leave the toothbrush off the charging base between uses. The base trickle-charges continuously. On a Ni-MH cell, that means constant shallow cycling — which compresses capacity faster than regular full-discharge cycles would.

Battery fade from continuous dock charging on the Triumph 4000

The Triumph 4000's base charger delivers a low-level inductive current whenever the handle is seated. Ni-MH cells tolerate this poorly over time — continuous trickle input causes voltage depression, where the cell accepts a charge but delivers less usable capacity per cycle. This effect compounds: each week on the dock accelerates the next drop. The fix is simple — charge to full, remove the handle, and return it only when noticeably weak.

Toothbrush not charging on the inductive base after battery replacement

If the charge indicator stays dark after fitting a new cell, the most common cause is seating alignment, not a faulty cell. The Triumph 4000 base uses inductive coupling, which requires the handle's internal coil to sit within a narrow positional range of the base coil. Confirm the handle is pressed fully down onto the base and that no debris is sitting in the base well. If the light still won't activate, measure voltage at the cell after 30 minutes on the base — you should see above 1.0V if inductive transfer is occurring.