About this replacement
Lenovo ThinkPad X1 Carbon 14 — 14.8V Li-Polymer Replacement Battery (45N1701)
This is a 14.8V, 3000mAh (44.4Wh) Li-Polymer cell for the Lenovo ThinkPad X1 Carbon 14 ultrabook. It fits the 20A7 and 20A8 chassis variants, along with the X1 Carbon 4th generation and related models. OEM part numbers covered include 45N1701, 45N1702, 45N1703, 00HW002, 00HW003, and SB10F46440.
- X1 Carbon 14 / 20A7 / 20A8 platform fit: These chassis share a 14.8V nominal rail, the same slim 5.34mm pack profile, and identical BMS handshake protocol — which is why one cell covers all three variants without modification.
- Bench tested on actual hardware: We cycled this cell on a ThinkPad X1 Carbon 20A8 and monitored the BMS through charge and load. The protection circuit held voltage within spec under sustained CPU and display load, and the pack accepted a full charge without triggering thermal cutoff.
- Post-install calibration on ThinkPad X1 Carbon: After fitting this cell, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
BIOS reporting battery health as poor after replacement
The ThinkPad BIOS stores battery state data in an EEPROM register tied to the old cell. When a new pack is installed, the BIOS reads stale cycle counts and Wh data, then flags the battery as degraded before it has run a single cycle. This is not a fault with the replacement cell — it is a data mismatch. Run the battery learn cycle in Lenovo Vantage under Power settings, or complete one full manual discharge-to-hibernate followed by an uninterrupted charge to 100%. After one to two full cycles, the BIOS recalibrates and the health warning clears.
Laptop shuts down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet mapped its discharge curve against the new cell's actual voltage profile. Under full CPU plus display load, the cell voltage drops faster than the old calibration predicts, and the system hits its low-voltage cutoff while the gauge still shows 20–30% remaining. The fix is calibration, not a swap — discharge fully to hibernate, then charge to 100% without interruption. After two to three cycles, the fuel gauge IC recalibrates to the new cell and the early shutdowns stop.