Acer Extensa 450 10.8V Replacement Battery 23.20040.051

Texas Instruments Extensa 450 Series — 10.8V Ni-MH Replacement Battery (23.20040.051)

This is a 10.8V, 4000mAh Ni-MH replacement battery for the Acer Extensa 450 notebook range. It fits the Extensa 450, 450T, 455, and 455T, among other models in the series. The OEM part number 23.20040.051 confirms fitment — cross-references include 91.48428.051, 9813495-0001, DR35, and DR35S.

• Extensa 450 and 455 series fit: These models share the same battery bay geometry, connector pinout, and voltage rail. The 10.8V nominal matches the charging circuit spec across the 450, 450T, 455, and 455T. One battery covers all four variants without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Extensa platform. The BMS accepted the cell without error flags, charge current stepped down correctly at top-of-charge, and the pack hit rated capacity within the first two conditioning cycles.
• Ni-MH first-cycle conditioning: 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 Ni-MH cell swap. Skip this step and the fuel gauge will read incorrectly for weeks.

BIOS reporting poor battery health immediately after installing a new cell

The Extensa BIOS stores charge history and health data in EEPROM on the old battery pack. When a new cell arrives, that EEPROM data is gone — the BIOS flags the battery as unknown or degraded because it has no cycle history to reference. This is not a fault with the replacement cell. Run the full discharge-to-hibernate then uninterrupted full-charge cycle once, and the BIOS learn cycle will rewrite its health estimate against actual measured capacity. After two full cycles, the health indicator should read normal.

Laptop shuts down at 20–30% remaining shown on screen

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The Extensa's gauge IC maps displayed percentage to cell voltage, and Ni-MH cells have a flatter discharge curve than the stored profile expects — the voltage cliff hits sooner than the gauge predicts. The fix is two or three full discharge-to-hibernate cycles followed by uninterrupted full charges. After calibration, the gauge tracks the Ni-MH curve correctly and shutdown at low percentage stops. If it persists past three cycles, check that hibernate threshold is set to 5% or below in Windows power settings.