Cobra 213021-N-001 Cordless Phone Replacement Battery 3.6V 1300mAh

Cobra 213021-N-001 / CP2055A Series — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 1300mAh Ni-MH battery for Cobra cordless phone handsets. It fits the 213021-N-001, CP1155, CP2055A, CP2058A, and at least ten additional Cobra models sharing the same cell format and connector. Voltage and physical dimensions match the original pack exactly: 50.57 × 42.47 × 14.35mm.

• CP1155 / CP2055A / CP2058A platform fit: These models share the same handset cavity depth, three-contact connector, and 3.6V charging rail from the base station. A single cell pack at this voltage works across the range without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Cobra cordless base. The NiMH chemistry accepted the trickle charge from the cradle without triggering a fault light, and voltage held at 3.6V nominal across all test cycles.
• First-charge protocol for NiMH handsets: After installing, seat the handset in the base and leave it on charge for a full 16 hours before first use. NiMH cells in cordless phones reach rated capacity only after a slow initial charge — skipping this produces noticeably short talk time on the first few cycles.

Base station charge light stays off or shows error on a new NiMH pack

Cobra base stations use a voltage-sensing circuit to confirm a battery is present before enabling charge current. A new NiMH pack that has sat in storage can drop below 3.0V, which the base reads as an open circuit or fault condition. The fix is a brief external boost — place the handset in the base, remove it after 30 seconds, then reseat it firmly. This brief contact is often enough for the sensing circuit to register a valid cell voltage and begin the charge cycle.

Talk time shorter than the original battery after the swap

NiMH cells do not deliver full rated capacity straight out of the box. Capacity builds across the first three to five complete charge-discharge cycles as the cell chemistry stabilises. If talk time seems low after the first charge, run the handset down until it signals low battery, then return it to the base for a full charge — repeat this three times. By cycle four, the pack should be delivering close to the rated 1300mAh.