Acer Extensa 500 Replacement Battery 9.6V 4000mAh 02K6524

Acer Extensa 500 Series — 9.6V Li-ion Replacement Battery (02K6524)

This is a 9.6V, 4000mAh (38.4Wh) Li-ion battery for the Acer Extensa 500 series notebook. It fits the Extensa 500, 500DX, 501, 501DX, and over two dozen additional models using the same battery bay and connector. OEM part numbers covered include 02K6524, 02K6525, BTP-1731, BTP-1831, and FRU 02K6526.

• Extensa 500 series compatibility: These models share the same 9.6V battery rail, physical bay dimensions (163.20 × 77.15 × 26.60mm), and connector pinout. The BMS in each unit expects the same charge-termination handshake, so one cell works across the full range without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles, monitoring the BMS cutoff thresholds and charge-termination voltage. The cell hits rated capacity and the protection circuit trips correctly at both ends of the voltage window.
• First-cycle calibration on the Extensa 500: After installing, run a full discharge to hibernate-cutoff, then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.

Why the Extensa 500 BIOS reports poor battery health immediately after a cell swap

The Extensa 500 stores battery health data in EEPROM on the original cell. When a new cell goes in, the BIOS reads no matching history and flags the battery as degraded or unknown. This is a data mismatch, not a fault with the replacement cell. Running a full discharge-to-hibernate followed by an uninterrupted charge to 100% lets the BIOS rewrite that learn-cycle data against the new cell. After one or two full cycles, the health indicator corrects itself.

Extensa 500 shutting down at 20–30% charge shown on the gauge

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge was trained on the old, degraded cell and misreads the new cell's state of charge. Under full CPU and display load, the laptop hits a voltage point the gauge misidentifies as near-empty and triggers a hard shutdown. Run two full discharge-to-hibernate and uninterrupted charge cycles — after the second cycle the gauge recalibrates and the shutdowns stop.