About this replacement
Asus Eee PC 1201N Series — 11.1V Li-ion Replacement Battery (A32-UL20)
This is an 11.1V, 4400mAh (48.84Wh) Li-ion replacement battery for the Asus Eee PC 1201N and related UL20 series netbooks. It replaces OEM part numbers A32-UL20 and A31-UL20, and fits a broad range of 1201 and UL20A variants. Install it when the original cell no longer holds a charge or the system shuts down unexpectedly under load.
- Eee PC 1201 and UL20A platform fit: These models share the same 11.1V three-cell battery rail, connector pinout, and BMS handshake protocol. The same physical pack and EEPROM data signature works across the 1201N, 1201T, 1201HA, and UL20A without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an Eee PC 1201N. The BMS communicated correctly with the BIOS, reported charge state accurately after calibration, and held voltage without tripping the protection circuit under sustained CPU and display load.
- First-cycle learn reset on the 1201N: After installation, run the battery down until the system hibernates, 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 a new cell
The Eee PC 1201N BIOS stores learned capacity data from the previous cell in firmware. When a new cell goes in, the BIOS compares live readings against that stale data and flags a health warning — not because the new cell is faulty, but because the reference values no longer match. Run one complete discharge to hibernate-cutoff followed by an uninterrupted charge to 100%. After one or two full cycles, the BIOS recalculates against the new cell's actual chemistry and the warning clears.
Eee PC 1201N shutting down at 20–30% charge shown
This happens when the cell cannot sustain the voltage the BIOS expects under combined CPU and display load. As the cell discharges toward the lower end, voltage sags below the firmware cutoff threshold before the fuel gauge reaches zero — so the system shuts down while the OS still shows charge remaining. It is a voltage cliff, not a capacity fault. Recalibrate by draining the battery fully to hibernate, then charging to 100% without interruption — this resets the fuel gauge IC baseline to match actual cell voltage at each state of charge.