About this replacement
Asus VivoBook S15 S530UA — 11.52V Li-ion Replacement Battery (B31N1729)
This is an 11.52V, 3550mAh (40.9Wh) Li-ion battery for the Asus VivoBook S15 S530UA and related S530 series laptops. It replaces OEM part numbers B31N1729 and 0B200-02920000. Fit covers the S530UA, S530UN, S5300UN, and over 150 additional S530 variants sharing this cell format.
- S530 series compatibility: The S530 line — UA, UN, UB, FA variants — shares a common battery bay geometry and BMS handshake protocol. All of them draw from the same 11.52V three-cell rail with an identical connector footprint, which is why one part number covers the entire range.
- Bench tested on actual hardware: We cycled this cell on an S530UA unit and monitored BMS communication throughout. The protection circuit engaged correctly at the low-voltage cutoff threshold, and charge acceptance from a depleted state held steady across three consecutive cycles.
- Post-swap calibration on the S530UA: After installing, run the laptop down to hibernate-level cutoff on battery alone — no AC — then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell data and clears the inaccurate health or capacity warning that commonly appears after any cell swap on this platform.
Why the S530UA BIOS flags a new battery as poor health
The S530UA stores battery health data in EEPROM on the old cell. When a new cell is fitted, 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 one full discharge-to-hibernate followed by a complete charge resets the learn cycle. After two to three cycles the health reading normalises and the warning clears.
Laptop shutting down at 20–30% remaining after battery swap
This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The S530 platform uses a coulomb counter that loses accuracy when cell chemistry or capacity changes. Under full load — CPU boost plus display brightness — the actual cell voltage can drop faster than the OS estimate, triggering an emergency shutdown before the gauge reaches zero. Run two full discharge-to-hibernate cycles without interruption and the fuel gauge IC will re-anchor to the new cell's actual voltage floor, typically around 10.4V at cutoff.