Lenovo Yoga S740-15IRH Compatible Battery 15.36V 4300mAh L18D4PF1

Lenovo Yoga S740-15IRH / C940-15IRH — 15.36V Li-Polymer Replacement Battery (L18D4PF1)

This is a 15.36V, 4300mAh (66.05Wh) Li-Polymer replacement battery for the Lenovo Yoga S740-15IRH and Yoga C940-15IRH ultrabooks. It fits the slim 15-inch chassis and connects directly to the existing battery connector without modification. OEM part numbers covered include L18D4PF1, L18M4PF1, 5B10T83737, and 5B10U65277.

• S740-15IRH and C940-15IRH compatibility: Both the S740 and C940 15-inch lines share the same 15.36V four-cell Li-Polymer architecture, identical BMS connector pinout, and the same charge controller handshake — so one cell fits both platforms without firmware differences between units.
• Bench tested on actual hardware: We cycled this cell on a Yoga S740-15IRH and confirmed the BMS initialised correctly, the charge controller accepted the full 66Wh capacity, and the protection circuit tripped at the correct low-voltage threshold without false cutoff.
• Post-installation discharge cycle on the Yoga S740/C940: After fitting this cell, run one full discharge until the laptop hibernates, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell data and clears the inaccurate health warning that appears after every cell swap on these Lenovo models.

BIOS reporting battery health as poor immediately after replacement on the Yoga S740/C940

Lenovo's embedded controller reads health data stored in the old cell's EEPROM and compares it against the new cell on first boot. Because the new cell has no charge history, the EC flags it as degraded or unknown. This is a firmware artefact — not a cell fault. Running one full discharge-to-hibernate followed by an uninterrupted charge to 100% completes the BIOS learn cycle and writes fresh calibration data. After two to three cycles the health indicator normalises.

Yoga S740-15IRH shutting down at 20–30% remaining after battery swap

The fuel gauge IC on the S740 motherboard calibrates its state-of-charge estimate against the old cell's discharge curve. With a new cell installed, the IC's model is out of sync and it hits a voltage cliff earlier than the actual cell capacity warrants. Under combined CPU and display load the voltage sags faster than the IC predicts, triggering an emergency shutdown. Discharge the laptop fully to hibernate cutoff — do not interrupt — then charge to 100% in one session. Repeat this cycle twice and the fuel gauge IC recalibrates to the new cell's actual discharge profile.