Telefunken CAS l Cordless Phone Replacement Battery 3.6V 1200mAh

Telefunken CAS l / CA51 — 3.6V Ni-MH Replacement Battery

This 3.6V, 1200mAh Ni-MH battery replaces the original pack in Telefunken CAS l and CA51 cordless handsets. It restores power to the handset so it can hold calls and sit on standby between charges. Dimensions are 42.40 × 49.90 × 14.40mm — measure your existing pack before fitting.

• CAS l and CA51 compatibility: Both models share the same 3.6V single-cell NiMH bay, connector orientation, and charge circuit. One battery fits both handsets without modification.
• Bench tested on actual hardware: We cycled this pack through the CAS l base station and confirmed the charge circuit accepted it cleanly. The NiMH chemistry drew a steady trickle current through full charge without triggering the base's overcharge cutoff.
• First-charge protocol for NiMH cordless handsets: Place the handset in the base and leave it for a full 16 hours before the first use. NiMH cells in cordless phones ship partially discharged; a slow first charge lets each cell balance and reach rated capacity. Skipping this step is the most common cause of short talk time complaints on new replacement batteries.

Base station charge light not activating on a new NiMH pack

Telefunken base stations check for a minimum voltage before starting the charge cycle. A new NiMH battery that has sat in storage can drop below 3.0V, which falls outside the base's acceptance window. When this happens, the charge indicator stays off and the handset shows low battery immediately after seating. To recover the pack, use a standalone NiMH charger to bring the voltage above 3.2V first, then seat the handset in the base — the base will then accept it and begin its normal charge cycle.

Range drops noticeably in rooms further from the base

DECT handsets maintain transmit power by drawing short high-current bursts from the battery. When a NiMH pack is not fully conditioned, its internal resistance is higher than rated, and voltage sags under those RF load bursts. The handset's RF module reduces transmit power to compensate, which cuts usable range. Run three full charge-and-use cycles to condition the cells — internal resistance falls with each cycle, and voltage sag under RF load stabilises at the correct level.