Cobra CP481 Cordless Phone Replacement Battery 3.6V 170mAh

Cobra CP481 — 3.6V Ni-MH Replacement Battery (CPB-405C)

This 3.6V, 170mAh Ni-MH battery replaces the original pack in the Cobra CP481 cordless phone handset. It restores talk time and standby capacity when the factory cell has degraded from repeated charge cycles. The CPB-405C is the direct OEM part number for this handset.

• CP481 handset fit: The CP481 uses a compact 3.6V Ni-MH cell with a specific connector orientation and cell footprint. This replacement matches those dimensions — 50.60 × 25.83 × 14.07mm — so the battery seats correctly in the handset compartment without modification.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on Ni-MH test equipment. The BMS accepted the slow trickle charge profile that cordless base stations deliver, and cell voltage stabilised at rated levels by cycle three.
• First charge on a cordless handset: After installing this battery, seat the CP481 handset in its base and leave it charging for a full 16 hours before the first call. Ni-MH cells shipped in partial-discharge state won't reach rated capacity on a short charge — the slow base-station trickle rate needs that full window.

Why the CP481 base station shows no charge light on a new Ni-MH pack

Ni-MH batteries lose voltage during storage — a cell sitting in a warehouse for months can drop below the threshold the base station uses to confirm a valid battery is present. When the base doesn't detect that voltage, the charge indicator stays off and no current flows. The fix is a brief external boost charge using a standalone Ni-MH charger at 0.1C to bring the pack up above 3.0V. Once the cell reaches that level, seat the handset in the base and the normal charge cycle will start.

Talk time shorter than expected after fitting the new battery

Ni-MH cells don't deliver full rated capacity straight out of the box — they need three to five full charge and discharge cycles to condition the cell chemistry. On cycles one and two, available capacity typically runs 20–30% below spec. Don't judge the battery on first use. Run the handset through full charge and discharge cycles three times, keeping it in the base after each full discharge, and measured talk time will climb toward the 170mAh rated capacity.