About this replacement
Toshiba Portege Z830 Series — 14.8V Li-Polymer Replacement Battery (PA5013U-1BRS)
This is a 14.8V 3000mAh (44.4Wh) Li-Polymer replacement battery for the Toshiba Portege Z830, Z835, Z935-P300, Z935, and over 35 additional Portege ultrabook variants. It uses OEM part number PA5013U-1BRS and slots into the same bay as the original cell. Voltage and connector match the original spec exactly.
- Z830/Z835/Z935 platform fit: These models share the same slim chassis, 14.8V power rail, and four-pin BMS connector — which is why one cell covers the full range. The BMS handshake protocol and charge termination voltage are identical across this Portege generation.
- Bench tested on actual hardware: We ran this cell on a Portege Z830 and Z935 unit. The BMS initialised correctly on first connection, charge acceptance started immediately, and the protection circuit triggered at the correct low-voltage cutoff without false trips under CPU and display load.
- First-cycle calibration on the Z830: After installing, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting poor battery health immediately after fitting a new cell
The Portege Z830 BIOS reads health data stored in the cell's EEPROM and compares it against the previous battery's charge history. A brand-new cell has no accumulated cycle data, so the BIOS flags it as degraded or unknown — not because the cell is faulty, but because the learn cycle hasn't run yet. Complete one full discharge to hibernate followed by a full uninterrupted charge. After one to two cycles the BIOS recalibrates and the health warning clears.
Z830 shutting down abruptly at 20–30% charge shown on screen
This is a voltage cliff issue. Under combined CPU and display load, the cell voltage drops faster than the fuel gauge IC can track, causing the system to hit the hardware undervoltage cutoff before the OS gauge reaches 0%. The fuel gauge IC needs two or three full discharge-charge cycles to map the new cell's discharge curve. Run the calibration cycle described above — after cycle three, the shutdown threshold and the displayed percentage should align at or below 5%.