About this replacement
Lenovo IdeaPad Duet 5 12IRU8 / 12IAU7 — 15.44V Li-Polymer Replacement Battery (L21C4PE3)
This is a 15.44V, 3150mAh (48.64Wh) Li-Polymer battery for the Lenovo IdeaPad Duet 5 12-inch hybrid tablet-laptop. It replaces OEM part numbers L21C4PE3, L21D4PE3, and L21L4PE3 across the 12IRU8 and 12IAU7 series. The flat 5.20mm profile fits the slim detachable chassis without modification.
- 12IRU8 and 12IAU7 coverage: Both series use the same 15.44V four-cell Li-Polymer configuration, identical connector pinout, and the same BMS handshake protocol — so one cell fits the full range of Duet 5 variants listed above.
- Bench tested on actual hardware: We ran this cell on a Duet 5 chassis and confirmed the BMS negotiated charge termination correctly at 15.44V. The fuel gauge IC communicated without error flags across the full charge cycle.
- First-cycle recalibration after swap: After installing, 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.
Duet 5 shutting down at 20–30% after a battery swap
The IdeaPad Duet 5 runs a combined CPU and display load that draws hard on the cell during intensive tasks. A new cell's EEPROM data has not yet synced with the BIOS fuel gauge IC, so the reported state-of-charge drifts badly in the first few cycles. The system reads a false low-voltage floor and triggers a protective shutdown before the cell is actually empty. Run two to three full discharge-to-hibernate and full-recharge cycles — the voltage floor recalibrates and shutdowns at false 20–30% stop.
BIOS reporting poor battery health immediately after installing a new cell
The BIOS reads health data from the EEPROM on the old or replacement cell, not from a live capacity test. A freshly swapped cell carries factory EEPROM values that don't match the learned data the BIOS was expecting from the original unit, so it flags "poor health" or shows 0% on first boot. This is a data mismatch, not a fault with the replacement cell. Run the battery learn cycle — full discharge to hibernate-cutoff, full uninterrupted charge to 100% — and the BIOS will rewrite its health register against the new cell's actual values.