Toshiba BT-311 Replacement Battery 3.6V 1300mAh Ni-MH

Toshiba BT-311 / FD-9859 Series — 3.6V Ni-MH Replacement Battery (TBR-8000)

This is a 3.6V, 1300mAh Ni-MH replacement battery for Toshiba cordless phone handsets. It fits the BT-311, FD-4809, FD-9839, FD-9859, and over 33 additional Toshiba DECT models. OEM part numbers TBR-8000 and TRB-1981 both reference this cell configuration.

• BT-311 and FD-series handset compatibility: These models share a common 3.6V single-cell NiMH pack format with the same connector pinout and physical envelope. The base station charges via the same contact rail across the range, so one cell spec covers the full group.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Toshiba FD-series handset. The BMS accepted charge from the base station on the first dock, and voltage held stable across the RF transmit window without sagging below the handset's low-battery cutoff threshold.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before using it. NiMH cells in storage arrive partially discharged — a slow first charge lets the cells reach full rated capacity before the handset's charge controller switches to trickle mode.

Why talk time stays short for the first few uses after a battery swap

NiMH cells don't deliver full rated capacity on cycle one. The chemistry needs three to five full charge-discharge cycles before the cells reach their 1300mAh rating. If talk time feels short immediately after installation, that's expected — it's not a faulty pack. Run the handset down fully and recharge it completely for each of the first few cycles, and capacity will build each time.

Base station charge light not activating after new battery is seated

A NiMH pack that has been sitting in storage can drop to a voltage the base station's charge controller reads as a fault condition rather than a depleted cell. The base expects to see a voltage above its acceptance threshold before it opens the charge circuit. If the charge indicator doesn't activate within two minutes of docking, remove the handset, wait 10 seconds, and re-seat it firmly. If the light still doesn't come on, check that the charge contacts on both the handset and base are clean — a thin layer of oxidation on either contact is enough to break the circuit at low NiMH voltages.