About this replacement
Toshiba Portege Z30 Series — 14.8V Li-Polymer Replacement Battery (PA5136U-1BRS)
This is a 14.8V, 3350mAh (49.58Wh) lithium-polymer replacement battery for the Toshiba Portege Z30 ultrabook. It uses OEM part number PA5136U-1BRS and fits the Z30, Z30-A-12U, Z30-A-M5S, Z30-A1301, and over 250 additional Z30-series variants. Install it when the original cell no longer holds a charge or BIOS flags battery health as degraded.
- Z30-series platform fit: All Z30-A variants share the same 14.8V four-cell Li-Polymer architecture, connector pinout, and BMS handshake protocol — which is why a single part number covers the full production run across regional SKUs.
- Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on a Z30-A unit. The BMS negotiated correctly with the Toshiba EC, charge current stepped down cleanly at the 80% threshold, and the cell reached 100% without voltage fault interruption.
- First-cycle conditioning on the Z30: After fitting, run the laptop on battery until it hibernates at low-battery cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears after every cell swap.
BIOS reporting poor battery health immediately after fitting the PA5136U-1BRS
The Z30's embedded controller reads health data from EEPROM on the battery's BMS board. When a new cell arrives, that EEPROM contains factory default values that don't match the EC's learned profile from the old battery. The EC interprets the mismatch as a degraded cell and flags it in BIOS and Windows battery settings. One complete discharge-to-hibernate followed by a full uninterrupted charge resets the learn cycle and writes fresh calibration data — the health warning clears without any BIOS update or driver change.
Portege Z30 shutting down at 20–30% charge shown on screen
This is a voltage cliff issue, not a fuel gauge error. Under combined CPU and display load, the cell's discharge curve drops steeply in the lower capacity band — voltage falls below the EC's cutoff threshold before the reported percentage reaches zero. The fuel gauge IC is reading state-of-charge against a stale discharge curve from the old cell. Run two full calibration cycles — full discharge to hibernate cutoff, full charge to 100% — so the fuel gauge IC maps its curve against the actual chemistry of the new cell. After the second cycle, the reported percentage at shutdown should align with real cell voltage near 13.2V.