Telstra 8400A Cordless Phone Compatible Battery 2.4V 600mAh

Telstra 8400A / 8450 Series — 2.4V Ni-MH 600mAh Replacement Battery

This is a 2.4V 600mAh Ni-MH battery for Telstra cordless phone handsets in the 8400A, 8450, CLS-8450, and Slim 8450 range. It replaces the original cell pack when talk time drops or the handset no longer holds a charge. Dimensions are 35.40 × 32.50 × 6.70mm — verify these against the existing cell before ordering.

• 8400A and 8450 series fit: All four models share the same 2.4V two-cell NiMH pack format and connector. The base station charges at a fixed low current matched to this voltage, so swapping between these handset variants carries no compatibility risk at the electrical level.
• Bench tested on actual hardware: We cycled this pack on a 2.4V NiMH charge profile and confirmed the cell pair reaches rated capacity without thermal runaway. BMS behaviour on these handsets is passive — the base station controls charge cutoff, not the pack itself.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in the base for a full 16-hour slow charge before use. NiMH cells in storage ship partially discharged; skipping the long initial charge leaves capacity on the table for the first several cycles.

Base station charge light not activating on a new NiMH pack

Telstra 8450-series bases use a voltage-sense circuit to confirm a battery is present before enabling the charge current. A pack that has sat in storage for months can drop below the threshold the base needs to see — typically around 2.0V — causing the charge indicator to stay dark. This is not a faulty battery or a faulty base. Place the handset in the cradle anyway and leave it for two to four hours; the base trickle-feeds enough current at low voltage to lift the pack above the acceptance threshold, after which normal charging resumes.

Range dropping mid-call after a battery swap

DECT transmitters in these handsets draw a short high-current burst during each RF packet transmission. A NiMH pack that has not completed its first few conditioning cycles has higher internal resistance, which causes voltage to sag under that RF load. The handset reads the sag as low battery and reduces transmit power — shrinking range noticeably. Run three to five full charge-and-use cycles to drive internal resistance down. After conditioning, the pack should hold above 2.2V under transmit load.