Lenovo IdeaPad L340-15IRH Replacement Battery 11.4V 3900mAh

Lenovo IdeaPad L340-15IRH / L340-17IRH — 11.4V Li-Polymer Replacement Battery (5B10T04975)

This is an 11.4V, 3900mAh (44.46Wh) Li-Polymer battery for the Lenovo IdeaPad L340-15IRH, L340-17IRH, and L340 SP/B series notebooks. It replaces the original cell when charge capacity has dropped or the battery no longer holds voltage under load. OEM part numbers covered: 5B10T04975, 5B10W67350, L18M3PF1, and SB10W67407.

• L340-15IRH and L340-17IRH compatibility: Both models share the same 11.4V three-cell architecture, connector pinout, and BMS handshake protocol. The L340 SP/B variant uses the same board layout, so one cell fits all three without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on L340-series hardware. The BMS negotiated correctly with the Lenovo EC firmware, held stable voltage across CPU and display load spikes, and reported capacity accurately after two calibration cycles.
• First-cycle reset after install: After fitting this battery, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell and clears the inaccurate health warning that appears on the first boot after every cell swap.

Why the L340 shuts down at 20–30% after a battery swap

The L340's fuel gauge IC retains calibration data from the old cell. When a new cell is installed, the IC maps voltage curves from the previous battery onto different chemistry characteristics. Under combined CPU and display load, the new cell hits a voltage cliff the IC wasn't expecting, and the EC interprets this as a critically low state-of-charge. Running two full discharge-to-hibernate and charge-to-100% cycles re-trains the fuel gauge IC against the actual voltage profile of the replacement cell. After those cycles, the reported percentage and the physical cutoff voltage align correctly.

BIOS showing battery health as "Poor" or "Replace Now" on a brand-new cell

Lenovo's BIOS reads health status from EEPROM data embedded in the battery's BMS board. On a new replacement cell, the EEPROM cycle count is zero and the rated Wh value may differ slightly from the original OEM figure, which some BIOS versions flag as a mismatch. This is a firmware interpretation issue, not a fault with the cell. Run the Lenovo Vantage battery gauge reset or perform one complete discharge-to-hibernate followed by a full uninterrupted charge — the BIOS health indicator typically clears to "Normal" once the learn cycle completes and the EC logs at least one full charge event.