Sony BP901 Cordless Phone Replacement Battery 3.6V 1500mAh

Sony BP901 / BT901 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 1500mAh Ni-MH battery for Sony cordless phone handsets using the BP901 or BT901 battery designation. It replaces the original pack when the handset no longer holds a charge or capacity has dropped noticeably. Dimensions are 73.36 x 48.30 x 14.44mm — measure your original before fitting if you are unsure.

• BP901 and BT901 compatibility: Both model codes reference the same cell format, voltage rail, and connector — Sony used both designations across different handset production runs. The BMS handshake and terminal layout are identical between them.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the bench. The BMS held cutoff correctly at low voltage and the base station accepted charge without throwing an error indicator after a full conditioning sequence.
• First-charge requirement 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 ship partially discharged and need a slow, uninterrupted first charge to reach rated capacity — skipping this step will leave the pack underperforming from day one.

Base station showing no charge or error light after fitting a new pack

A Ni-MH pack that has sat in a warehouse for several months can drop to a voltage the base station interprets as a fault rather than a depleted battery. Sony DECT bases typically expect the pack to be above a minimum acceptance threshold before initiating a charge cycle. If the error light stays on, remove the handset, wait 30 seconds, and reseat it firmly — this resets the base's detection logic. If the error persists, the pack may need a brief trickle from an external Ni-MH charger to bring voltage above 3.0V before the base will accept it.

Handset not re-pairing with the base after battery replacement

Removing a Ni-MH pack from a DECT handset cuts power completely, and some Sony models drop their pairing registration when that happens. The handset boots as if it has never been paired. To fix this, navigate to the handset's registration menu — usually under Settings or Phone Setup — and run the pairing sequence again with the base in registration mode. The base PIN is typically 0000 unless it has been changed. Once re-paired, the handset should resume normal operation immediately.