About this replacement
Avaya TransTalk 9040 Series — 3.6V Ni-MH Replacement Battery (K40SB-H10826)
This is a 3.6V, 750mAh Ni-MH replacement battery for the Avaya 9040, 9040A, 9631, and TransTalk 9040 series cordless handsets. It replaces OEM part numbers K40SB-H10826, 32793BP, and 108586559, among others. Swap it when the original pack no longer holds a charge or the handset dies mid-call.
- TransTalk 9040 and 9631 compatibility: These handsets share the same 3.6V three-cell Ni-MH pack format, identical connector pinout, and the same base station charging circuit. One battery fits both.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on a TransTalk 9040 base unit. The charging circuit accepted the new pack without error, and the BMS completed a full charge cycle without cutoff.
- First-charge protocol for Ni-MH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped in a partially discharged state need a slow initial charge to reach rated capacity — skipping this step leaves you with a noticeably shorter first charge.
Talk time shorter than the original battery after replacement
Ni-MH cells don't deliver full rated capacity on cycle one. The 750mAh rating is reached after three to five full charge-discharge cycles. Each cycle, the cells shed a small amount of residual memory and align electrochemically. Run the handset until it cuts off, return it to the base for a full charge, and repeat — by cycle five, talk time will be at or near the rated spec.
Base station shows no charge or error light after installing new pack
Ni-MH batteries lose voltage during storage. If the pack voltage drops below roughly 3.0V, some Avaya base stations reject the charge initiation and flag an error light instead of charging. Remove the handset, hold the power button for five seconds to fully discharge any residual, then reseat it firmly in the base. The charging circuit should detect the pack on the next insertion and begin a trickle charge to bring it up to threshold.