About this replacement
Sony Portable Reader PRS-900 — 3.7V Li-ion Replacement Battery (1-756-915-11)
This 3.7V, 1400mAh Li-ion cell replaces the original battery in the Sony Portable Reader PRS-900 and PRS-900BC, also sold as the Sony Reader Daily Edition. It fits models using OEM part numbers 1-756-915-11, PRSA-BP9, and PRSA-BP9//C(U3). Swap it in when the original cell no longer holds enough charge to get through a reading session.
- PRS-900 and PRS-900BC compatibility: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. A single cell covers both units — no hardware differences affect fitment.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on PRS-900 hardware. The BMS accepted the new cell without fault codes, and the firmware recognised the pack without requiring a manual reset.
- Wi-Fi sync and charge management: The PRS-900 draws significantly more current during Wi-Fi sync than during page turns. After installing this cell, complete a full USB charge cycle before enabling wireless sync — the firmware needs a full charge reference point to report battery percentage accurately after a cell swap.
Why the PRS-900 shows a low battery warning immediately after a new cell
Replacement cells ship at storage voltage — typically between 3.6V and 3.7V — which sits just above the device's low-battery threshold. The PRS-900 firmware reads this as a near-depleted pack before any calibration has occurred. This is not a faulty cell. Connect the device to a USB charger and allow it to reach a full charge before first use. Once the firmware completes one full charge cycle, the battery percentage indicator will report correctly.
PRS-900 not powering on after battery replacement
If the device shows no response after swapping the cell, the new battery's resting voltage may have dropped below the PRS-900's minimum boot voltage during storage. The device will not attempt to power on below approximately 3.4V. Connect the reader to a USB charger and leave it for at least 10 minutes without pressing the power button — the charging circuit will pre-charge the cell to a level where the boot sequence can start. After 10 minutes, press and hold the power button for five seconds.