About this replacement
Toshiba Satellite NB200 / NB205 Series — 10.8V Li-ion Replacement Battery (PA3731U-1BRS)
This is a 10.8V, 6600mAh Li-ion replacement battery for the Toshiba Satellite NB200, NB201, NB205, and NB200-110 series netbooks. It replaces OEM part numbers PA3731U-1BRS, PA3734U-1BRS, PA3733U-1BRS, PA3732U-1BAS, and PABAS209, among others. The connector pinout and BMS communication protocol match the original Toshiba cell.
- NB200 / NB201 / NB205 platform fit: These three models share the same battery bay geometry, connector, and SMBus handshake protocol — the BMS on all variants expects the same charge parameters and cell identification data, so one battery covers the entire NB-series line.
- Bench tested on actual hardware: We ran this cell on an NB200 and confirmed the BMS accepted the EEPROM data without flagging an incompatible cell. Charge cycles completed normally from 0% to 100% without the charger dropping out early.
- First-cycle calibration on the NB200: After installation, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This forces the fuel gauge IC to re-learn the new cell's capacity curve and clears the inaccurate battery health warning that appears in the BIOS after any cell swap.
Why the NB200 BIOS reports poor battery health immediately after a replacement
The NB200 stores battery health data in EEPROM on the original cell. When you swap the cell, the BIOS reads stale or mismatched EEPROM values and flags the battery as degraded before it has ever run a cycle. This is a firmware read issue, not a cell defect. Running the battery learn cycle — full discharge to hibernate cutoff, then a full uninterrupted charge — rewrites the fuel gauge calibration against the new cell's actual chemistry. After one or two complete cycles, the BIOS health status corrects itself.
NB200 shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated to the new cell's voltage-to-capacity curve. The displayed percentage is ahead of actual cell voltage, so the laptop hits the low-voltage cutoff while the OS still shows charge remaining. The fix is a calibration cycle: let the laptop discharge under normal load until it hibernates, then charge to 100% without interruption. After two full cycles the gauge and the cell's real voltage floor align — shutdowns at false percentages stop.