Cobra 213021-N-001 Replacement Battery 3.6V 700mAh Ni-MH

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

This is a 3.6V, 700mAh Ni-MH battery for Cobra cordless phones including the 213021-N-001, CP1155, CP2055A, and CP2058A handsets, plus ten additional compatible models. It replaces the original rechargeable pack that sits inside the handset and powers both talk and standby modes. Dimensions are 50.79 × 42.40 × 14.23mm — measure your existing pack before ordering if you are unsure.

• CP-series handset compatibility: These Cobra models share the same 3.6V three-cell Ni-MH format, identical connector orientation, and matching physical footprint. The base station charges at a voltage rail tuned for this chemistry, so no adapter or modification is needed.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a CP-series handset. The base station accepted charge on the first insertion, the charge indicator lit correctly, and the BMS held stable voltage throughout the drain cycle.
• First-charge protocol for Ni-MH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped from storage are partially depleted — a slow first charge is what brings them to rated capacity. Skipping this step is the single most common reason talk time feels short out of the box.

Base station charge light stays off or shows error on a new Ni-MH pack

Cobra base stations use a delta-V detection circuit to confirm a valid Ni-MH pack is present before committing to a charge cycle. A battery discharged below roughly 3.0V during shipping or storage can read as absent or faulty to that circuit. The fix is a trickle-start: leave the handset seated in the base undisturbed for at least two hours. Most base stations will detect the rising cell voltage and switch to normal charge mode automatically. If the error persists after two hours, check that the handset contacts are clean and fully seated against the base cradle pins.

Range drops mid-call after replacing the battery

DECT transmit power is drawn in short high-current bursts. When a Ni-MH pack hasn't been fully conditioned, internal resistance is higher than normal and voltage sags under that RF load. The handset interprets the voltage dip as low battery and reduces transmit power to protect the pack — which cuts range. This corrects itself over three to five full charge-discharge cycles as the cells reach rated capacity. Run the handset down to the low-battery indicator, then return it to the base for a full charge, and repeat that cycle before assuming the battery is faulty.