About this replacement
Lenovo Yoga Slim 7 Carbon 13IAP7 — 7.72V Li-Polymer Replacement Battery (L21C4PH3)
This 7.72V, 6250mAh (48.25Wh) Li-Polymer battery replaces the original cell in the Lenovo Yoga Slim 7 Carbon 13IAP7 series. It fits models including the 82U9003GPB, 82U90040AX, 82U9004GMX, and 82U9004YJP, along with over 114 additional variants in the same line. OEM part numbers covered include L21C4PH3, L21D4PH3, L21L4PH3, and L21M4PH3.
- Yoga Slim 7 Carbon 13IAP7 compatibility: All listed variants share the same 7.72V two-cell Li-Polymer configuration, connector pinout, and BMS handshake protocol. The fuel gauge IC communicates over SMBus — the EEPROM data embedded in this cell matches what the Lenovo EC expects on first recognition.
- Bench tested on actual hardware: We ran this cell on a Yoga Slim 7 Carbon 13IAP7 unit under mixed CPU and display load. The BMS held steady through charge and discharge cycles with no cutoff trips, and the EC recognised the cell without throwing an unknown battery warning.
- Post-swap calibration on Yoga Slim 7 Carbon: After fitting this cell, run one full discharge down to hibernate cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell chemistry and clears the inaccurate health warning that appears on the first boot after any cell swap.
Laptop shutting down at 20–30% remaining after battery swap
This happens when the fuel gauge IC still holds calibration data from the degraded original cell. Under full CPU plus display load, the new cell hits a voltage cliff that the old calibration data does not expect, and the EC triggers an emergency shutdown. The fix is not a fault with the replacement cell — it is a calibration gap. Run two full discharge-to-hibernate and charge-to-100% cycles, and the fuel gauge IC will re-map the voltage curve against the actual chemistry of the new cell. After the second cycle, the reported percentage at shutdown should align with real remaining capacity.
BIOS reporting battery health as poor immediately after installation
The Lenovo EC reads cycle count, design capacity, and state-of-health from EEPROM registers on the cell. A new cell ships with a cycle count of zero and full design capacity in its EEPROM — but the BIOS compares this against the learn cycle data it accumulated from the previous cell, and the mismatch triggers a poor health flag. This is not a hardware fault. Open Lenovo Vantage, navigate to Power, and run the battery gauge reset function. If Vantage is not installed, discharge fully to hibernate cutoff and charge to 100% twice — the EC will rewrite its learn cycle data and the health warning will clear.