Radio Shack 43-3529 Cordless Phone Replacement Battery 3.6V 800mAh

Radio Shack 43-3529 / 43-3538 Series — 3.6V Ni-MH Replacement Battery (BBTY0457001)

This is a 3.6V, 800mAh Ni-MH battery pack for Radio Shack cordless phone handsets. It fits the 43-3529, 43-3538, 43-3553, 43-3554, and more than two dozen additional Radio Shack handset models. The pack replaces OEM part numbers BBTY0457001, BBTY0458001, BT-446, GP80AAALH3BMX, and BT1005.

• Multi-model fit across the 43-series lineup: These handsets share the same 3.6V three-cell AAA Ni-MH configuration, matching connector pin-out, and identical BMS handshake with the base charging cradle — which is why one pack covers so many model numbers across this Radio Shack cordless range.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a 43-series handset. The base station accepted the charging handshake without error, and the BMS held voltage steady across the full discharge curve without false low-battery cutoffs.
• First-charge protocol for Ni-MH cordless packs: Place the handset in the base cradle for a full 16 hours before first use. Ni-MH cells shipped in a partially discharged state do not reach rated capacity on a short initial charge — skipping this step is the single most common cause of shorter-than-expected talk time from day one.

Range drops mid-call after fitting a new Ni-MH pack

The DECT radio module in these handsets draws a surge of current each time it transmits. A Ni-MH pack that has not completed its first few conditioning cycles shows a sharper voltage sag under that RF load. When voltage sags below the radio module's minimum operating threshold, transmit power drops — and so does range. Run three to five full charge-discharge cycles through normal use, and the cells reach rated capacity. After that, voltage sag under RF load returns to normal levels.

Base station shows no charge light or flashes an error after battery swap

Ni-MH packs that have sat in storage can arrive with a resting voltage below the level the base station expects before it begins a charge cycle. Some Radio Shack bases read a voltage below roughly 3.0V as a fault condition and refuse to initiate charging. Remove the handset, wait 30 seconds, and reseat it firmly — full contact on both charging pins is required. If the error persists, check resting voltage across the battery terminals with a multimeter; a reading above 3.0V confirms the pack is within the base's acceptance window and the issue is a contact or seating problem, not the battery itself.