Saft STB958 Cordless Phone Replacement Battery 3.6V 700mAh

Saft STB958 — 3.6V Ni-MH Replacement Battery for Cordless Phones

This is a 3.6V, 700mAh Ni-MH replacement battery for cordless DECT handsets that take the Saft STB958 pack. It fits the cell compartment and connector used across a range of home and office cordless phone handsets. Swap it in when the original no longer holds a useful charge or fails to register on the base station.

• STB958 platform fit: Handsets sharing this battery use the same 3.6V single-cell Ni-MH rail, matching connector pitch, and cell footprint — 46 × 31 × 10.5mm. No modification needed to seat the pack.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a DECT handset base. The BMS accepted the NiMH voltage profile without error and the cell reached rated capacity by the fourth cycle.
• First-charge protocol for NiMH handsets: After installing, seat the handset in the base for a full 16 hours before the first use. NiMH cells shipped from storage sit below the voltage the base expects — a slow initial charge lets them reach rated capacity rather than being cut short by a premature top-off signal.

Base station charging error on a new NiMH pack

Cordless phone bases use a delta-V detection circuit to confirm a battery is accepting charge. A NiMH cell that has discharged in storage may sit below the voltage window the base needs to initiate that handshake. The base then throws a charge error or shows a fault light — not because the battery is faulty, but because voltage is too low for the circuit to latch on. Place the handset in the base and leave it undisturbed for at least 16 hours; most base stations will begin trickle-charging even a deeply discharged pack and the error will clear once voltage climbs above roughly 3.2V.

Range drops noticeably mid-call after a battery swap

DECT handsets draw a surge of current each time the transmitter fires — typically every 10ms during a call. A NiMH cell that has not yet been conditioned cannot sustain voltage under that load, so the transmit power sags and effective range shrinks. This is not a fault with the battery or the phone — it is a capacity issue that resolves after three to five full charge-discharge cycles. Run the handset to low battery, return it to the base for a full charge, and repeat; by cycle four the cell should hold voltage steadily enough to maintain full transmit power across the room.