Acer Aspire 3661WLMi Replacement Battery 14.8V 4400mAh

Acer Aspire 3661WLMi Series — 14.8V Li-ion Replacement Battery (BT.00803.014)

This 14.8V, 4400mAh (65.12Wh) Li-ion battery replaces the original cell in the Acer Aspire 3661WLMi and over 30 compatible Aspire models. It slots into the standard battery bay and connects via the original locking latch — no tools needed. Voltage and connector pinout match the OEM specification exactly.

• Aspire 3600 / 5600 series compatibility: These models share the same 14.8V four-cell battery rail, connector layout, and BMS handshake protocol. That is why one part number — BT.00803.014 — covers units like the 3682WXC, 5600AWLM, and 5601AWLMi alongside the 3661WLMi.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a 3661WLMi chassis. The BMS communicated current draw accurately to the OS throughout, and the protection circuit tripped correctly at low-voltage threshold without needing a manual reset.
• First-cycle calibration on the Aspire platform: After fitting, run the laptop on battery until it hibernates at cutoff — do not interrupt it. Then charge uninterrupted to 100%. This single cycle resets the BIOS battery learn cycle and clears the inaccurate health or low-capacity warning that appears after every cell swap on Aspire hardware.

BIOS reporting poor battery health immediately after fitting a new cell

The Aspire BIOS reads health data stored in the battery's EEPROM, not from live cell measurements. A new cell ships with factory EEPROM values that do not yet match the BIOS's learned baseline for your chassis. The system flags this as degraded health because the stored cycle count and capacity data look foreign. Run one full discharge-to-hibernate followed by an uninterrupted charge to 100% — the BIOS learn cycle overwrites the stale EEPROM data and the health warning clears.

Laptop shuts down at 20–30% charge shown on the gauge

This is a voltage cliff, not a fuel gauge error. Under combined CPU and display load, cell voltage drops faster than the gauge predicts, hitting the BMS cutoff before the percentage reaches zero. It happens most often when the old fuel gauge IC calibration from the previous battery is still active. Discharge fully to hibernate cutoff twice in a row to force the fuel gauge IC to recalibrate against the new cell's actual discharge curve. After two full cycles the shutdown point should track below 5%.