AT&T 102 Cordless Phone Replacement Battery 3.6V 700mAh

AT&T 102 / 103 Series — 3.6V Ni-MH Replacement Battery (BT103)

This is a 3.6V, 700mAh Ni-MH battery pack for AT&T cordless phone models including the 102, 103, 249, and EP590-2. It replaces OEM part numbers BT103 and 249. It fits directly into the handset battery compartment and restores power to handsets where the original cell no longer holds a useful charge.

• 102 / 103 / 249 / EP590-2 platform fit: These AT&T handsets share the same 3.6V single-cell NiMH pack format, connector orientation, and physical footprint — one battery covers the full group without modification.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a 102-series handset. The BMS accepted charge from the base cradle without error, and cell voltage held stable through multiple full cycles.
• First charge protocol for NiMH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before the first use. NiMH cells in cordless phones reach rated capacity only after a slow initial charge — skipping this step leaves the cells under-formed and talk time will fall short of what the pack can actually deliver.

Base station charging error on a new NiMH pack

AT&T base stations check incoming voltage before starting a charge cycle. A fresh NiMH pack from storage can sit below 3.0V — low enough that the base reads it as a fault rather than a dischargeable cell. This is not a defective battery or a broken base. Place the handset in the cradle and leave it undisturbed; most AT&T bases will retry the charge circuit after a few minutes and accept the pack once voltage climbs above the threshold. If the error light persists past 30 minutes, remove and reseat the handset to trigger a fresh detection cycle.

Range drops mid-call after a battery swap

DECT transmitters on these handsets draw a short current spike each time the radio fires. If the NiMH cells are under-formed — common in the first three to five cycles — internal resistance is higher than normal, and voltage sags under that RF load. The handset reads low voltage, backs off transmit power, and range shrinks noticeably. Run three to five full charge-and-use cycles to condition the cells. Internal resistance drops as the cells form, voltage holds steadier under load, and transmit power returns to spec.