About this replacement
Lenovo Yoga Slim 9 14IAP7 — 15.52V Li-Polymer Replacement Battery (5B11F35903)
This is a 15.52V, 4700mAh (72.94Wh) Li-Polymer battery for the Lenovo Yoga Slim 9 14IAP7 ultrabook. It fits across the 82T0 series, covering retail variants from multiple regions including the 82T0001ETA, 82T0001XUK, and 82T0002ESA. Cross-references include OEM part numbers L21B4PH1, L21C4PH1, L21D4PH1, L21L4PH1, L21M4PH1, and SB11F35904.
- 82T0 series compatibility: All Yoga Slim 9 14IAP7 variants under the 82T0 product code share the same four-cell Li-Polymer configuration, 15.52V nominal rail, and physical connector spec. That is why a single cell services 139-plus regional SKUs without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the 14IAP7 platform. The BMS handshook correctly with the Lenovo EC firmware, reported capacity data over SMBus, and did not trigger any OVP or UVP cutoff events at normal load.
- BIOS battery learn cycle after install: After fitting this cell, run the laptop down to hibernate-cutoff on battery only — no AC — then charge uninterrupted to 100%. This resets the BIOS learn cycle, clears the inaccurate "poor health" warning that appears after a cell swap, and gives the fuel gauge IC a clean calibration baseline against the new chemistry.
BIOS reporting battery health as poor immediately after replacement
The Lenovo BIOS reads health data from EEPROM on the battery pack, not from a live capacity measurement. When a new cell goes in, the EEPROM data does not match what the system recorded for the old pack, so the BIOS flags it as degraded or unknown. This is a firmware state issue, not a fault with the replacement cell. One complete discharge-to-hibernate followed by an uninterrupted charge to 100% triggers the battery learn cycle and writes fresh data to the gauge IC. After that cycle, the health status in Lenovo Vantage and the BIOS should read normal.
Laptop shuts down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The displayed percentage does not match real cell voltage, so the system hits a low-voltage protection threshold before the gauge reaches 0%. Under combined CPU and display load, voltage sag accelerates this gap. The fix is two or three full discharge-to-charge cycles to let the gauge IC map the new cell's curve accurately. After calibration, the fuel gauge tracks actual cell voltage and the early shutdowns stop — typically resolved once the cell has been below 3.2V per cell and back to full charge twice.