Sony BP-T18 Cordless Phone Replacement Battery 3.6V 1300mAh

Sony BP-T18 / BP-T24 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 1300mAh Ni-MH replacement battery for Sony cordless phone handsets. It fits the BP-T18 and BP-T24 battery footprints, covering the SPP-933, SPP-934, and over 30 additional Sony DECT models. Swap it in when the original pack no longer holds a charge between calls.

• SPP-933 and SPP-934 compatibility: These handsets share the same battery bay geometry, voltage rail, and three-contact charging interface, which is why a single cell covers both. The base station expects a 3.6V NiMH pack — no BMS handshake is required.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Sony SPP-series handset. The base station accepted the battery immediately, and the handset reported full signal strength under normal RF load without voltage sag.
• First-charge conditioning for NiMH cordless packs: After installing, seat the handset in the base for a full 16-hour slow charge before first use. NiMH cells in cordless phone packs need this initial conditioning cycle to reach rated 1300mAh capacity — skipping it will leave the pack delivering noticeably less talk time from day one.

Range reduced after fitting a new NiMH pack

DECT handsets pull a short burst of higher current each time the radio transmits. A NiMH cell that hasn't completed its conditioning cycles has higher internal resistance, and that resistance causes the voltage to sag during each transmit burst. The base station interprets the weaker signal as distance and reduces output power to compensate. After three to five full charge and discharge cycles, internal resistance drops and the transmit voltage stabilises — range returns to normal.

Base station shows no-charge or error light after battery swap

New NiMH cells ship in a partially discharged state and can measure below 3.0V after storage. Some Sony base stations won't initiate a charge cycle if the incoming voltage reads too low, showing a fault light instead. Remove the handset, wait 30 seconds, and re-seat it firmly — this resets the charge controller. If the fault persists, check the battery contacts are clean and making full contact; a light coat of isopropyl alcohol on the contacts clears any oxidation that causes a false low-voltage reading.