Sony VAIO Duo 11 VGP-BPS31 Replacement Battery 7.4V 4400mAh

Sony VAIO Duo 11 — 7.4V Li-Polymer Replacement Battery (VGP-BPS31)

This is a 7.4V, 4400mAh (32.56Wh) lithium-polymer replacement battery for the Sony VAIO Duo 11 convertible hybrid. It fits the SVD11215CW/B, SVD11215CG, SVD11216PGB, and 24 additional SVD11-series variants. OEM part numbers covered include VGP-BPS31, VGP-BPL31, and VGP-BPS31A.

• SVD11-series compatibility: All covered models share the same 7.4V two-cell Li-Polymer architecture, identical connector pinout, and matching BMS handshake protocol. Sony used this battery across the full Duo 11 production run without revision, so one cell fits every unit on the list.
• Bench tested on actual hardware: We ran this cell on a VAIO Duo 11 unit and confirmed the BMS completed its charge cycle without triggering overcurrent cutoff. The BIOS battery dialogue returned a valid Wh reading on first boot with no error flags.
• BIOS learn cycle after install: After fitting this cell, run the laptop down to hibernate cutoff under normal load — screen on, Wi-Fi active — then charge uninterrupted to 100%. This forces the fuel gauge IC to calibrate against the new cell and clears the inaccurate health warning the BIOS flags after every battery swap.

Why the VAIO Duo 11 BIOS reports poor battery health after a cell swap

The VAIO Duo 11 stores charge cycle counts and health metrics in EEPROM on the original battery pack. When a new cell goes in, that data is absent or mismatched, so the BIOS reads the replacement as degraded even though it is not. This is a data gap, not a hardware fault. Running one complete discharge-to-hibernate then a full uninterrupted charge gives the fuel gauge IC enough data to write new baseline values. After one to three cycles, the health indicator in BIOS and Windows normalises.

VAIO Duo 11 shutting down at 20–30% charge shown on screen

This happens when the original cell has aged enough that it cannot hold voltage under the combined load of the CPU, backlit display, and wireless radio — even though the OS gauge still shows charge remaining. The cell hits a voltage cliff and the BMS trips before the gauge catches up. A new 4400mAh cell restores the flat discharge curve that the fuel gauge was calibrated to expect. After installing, confirm the shutdown no longer occurs by running a full load cycle and checking that the battery voltage stays above 6.8V through the 20–30% window.