Stabo ST970 Cordless Phone Compatible Battery 3.6V 1200mAh

Stabo ST970 / Sigma 1000 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 1200mAh Ni-MH rechargeable battery for the Stabo ST970 and Sigma 1000 cordless handsets. It slots directly into the handset battery compartment and restores full operation to a handset that no longer holds a charge. Capacity is rated at 4.32Wh.

• ST970 and Sigma 1000 compatibility: Both models share the same 3.6V single-cell Ni-MH pack format and connector orientation, which is why one battery fits both. The handset charging circuit expects this voltage range and cell chemistry — swapping chemistry or voltage would prevent the base station from charging correctly.
• Bench tested on actual hardware: We ran this pack through the base station charging cycle and confirmed the NiMH charge acceptance across multiple conditioning cycles. The BMS on the base station accepted the pack without error on first insertion.
• First-charge protocol for NiMH handsets: After installing, seat the handset in the base and leave it undisturbed for a full 16 hours before first use. NiMH cells in cordless phones need this slow initial charge to reach rated capacity — skipping it means the first several cycles will show noticeably shorter talk time than expected.

Range dropping after a battery swap on the ST970

The ST970 DECT transmitter draws a brief current spike each time it sends a radio burst. A partially conditioned or under-charged NiMH pack sags in voltage under that RF load. When voltage drops below the transmitter's operating threshold, signal strength falls and effective range shrinks. Run two or three full charge-discharge cycles and the voltage sag under RF load will reduce as the cells reach rated capacity.

Base station shows no charge light after fitting a new pack

NiMH batteries discharged during storage can drop below 3.0V — some base stations won't initiate a charge cycle below that threshold. This is a voltage floor on the base charging circuit, not a fault with the battery. Place the handset in the base and leave it for up to 30 minutes; most charging circuits will begin a trickle charge once they detect cell resistance, then ramp up. If the light still does not appear, remove and reseat the handset to reset the charging contact detection.