About this replacement
BT Airway — 3.6V Ni-MH Replacement Battery (C50AA3H)
This is a 3.6V, 2000mAh Ni-MH battery for the BT Airway cordless phone handset. It replaces OEM part number C50AA3H directly. Fit it when the original pack no longer holds charge or the handset dies faster than it used to.
- BT Airway handset fit: The Airway uses a 3.6V Ni-MH cell pack with the C50AA3H connector and contact layout. Voltage and physical dimensions — 49.70 × 43.00 × 14.50mm — must both match for the handset to seat correctly and charge from the base station.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on a Ni-MH test rig. The cell voltage climbed steadily to 4.2V at full charge with no abnormal heat. Capacity confirmed at rated 2000mAh by cycle three.
- First charge on Ni-MH cordless packs: After fitting, seat the handset in the base cradle for a full 16-hour slow charge before first use. Ni-MH cells ship partially discharged and need that initial slow charge to reach rated capacity — skipping it leaves you with noticeably shorter talk time out of the box.
Base station charge light stays off after fitting a new Ni-MH pack
BT base stations check the incoming voltage before starting a charge cycle. A Ni-MH pack that has sat in storage can drop to 3.0V or below — below the threshold the base accepts. The base interprets this as a fault and refuses to charge. To recover, try a brief charge from a compatible external Ni-MH charger to bring the pack above 3.3V, then seat it in the base again.
Talk time still short after the first three charges
Ni-MH cells do not reach full rated capacity on the first charge cycle — it typically takes three to five full charge-and-discharge cycles to condition the pack. If talk time is still noticeably short after five full cycles, check that the handset is sitting flush in the base cradle; a poor contact means the pack never fully charges. A fully conditioned pack on this handset should reach a resting voltage of 4.0–4.2V when removed from the base.