About this replacement
Avaya TransTalk 9040 / 9631 — 3.6V Ni-MH Replacement Battery (K40SB-H10826)
This 3.6V, 2000mAh Ni-MH battery replaces the original pack in the Avaya TransTalk 9040, 9040A, and 9631 cordless handsets. It matches OEM part numbers K40SB-H10826, 32793BP, and 108586559, among others. Capacity figure is taken directly from product data — 7.2Wh total energy.
- TransTalk 9040 and 9631 platform fit: Both handsets share the same 3.6V single-cell Ni-MH voltage rail, identical connector pinout, and the same physical bay dimensions (114.20 × 60.00 × 23.40 mm). One battery part number covers all variants in this family because the base station charges at the same trickle rate across the lineup.
- Bench tested on actual hardware: We cycled this pack through the TransTalk base station and confirmed the BMS accepted the charge handshake without error. Voltage at full charge sat within the expected Ni-MH range. No cutoff events were triggered during discharge under normal handset load.
- First-charge conditioning for Ni-MH handsets: After installing this battery, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped from storage are partially discharged. A slow first charge lets each cell reach rated capacity and prevents premature capacity fade across subsequent cycles.
Talk time shorter than the original battery after replacement
Fresh Ni-MH cells do not deliver full rated capacity on the first cycle — this is normal chemistry, not a defect. The cells need three to five full charge-and-use cycles before they reach 2000mAh. Each cycle, the internal resistance drops slightly and usable capacity climbs. Run the handset until the low-battery indicator fires, return it to the base for a full charge, and repeat — by cycle five, talk time will stabilise at rated capacity.
Base station shows no charge or error light after battery swap
Ni-MH packs sitting in warehouse storage can drop to a voltage the TransTalk base station reads as a fault — typically below 3.0V on a 3.6V cell. The base charges at a low trickle rate and the detection circuit may not initiate if it sees that voltage on first contact. Remove the handset, wait 10 seconds, and re-seat it firmly so all three charge contacts are flush. If the error light persists, check that the base is drawing mains power and the contacts on both the base and handset are clean and undamaged.