About this replacement
Dell Latitude 5289 / 7390 2-in-1 — 11.4V Li-Polymer Replacement Battery (X49C1)
This is an 11.4V, 3850mAh (43.89Wh) lithium-polymer battery for the Dell Latitude 5289 2-in-1 and Latitude 7390 2-in-1 convertible laptops. It replaces OEM part numbers X49C1, 71TG4, and CFX97. If your original cell has swollen, stopped holding charge, or is flagged as degraded in Dell's battery report, this cell swaps directly into that slot.
- Latitude 5289 and 7390 2-in-1 compatibility: Both models share the same 11.4V three-cell Li-Polymer architecture, identical connector pinout, and the same BMS communication protocol over SMBus. The same OEM part numbers — X49C1, 71TG4, CFX97 — appear across both platforms, which is why one cell covers both.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a Latitude 5289 chassis. The BMS accepted the cell without fault codes, the SMBus handshake completed cleanly, and charge progression through all three stages — precharge, CC, CV — behaved as expected.
- Post-install learn cycle for Latitude 2-in-1s: After fitting, discharge the laptop fully until it hibernates, then charge uninterrupted to 100% without interruption. This forces the BIOS fuel gauge IC to re-calibrate against the new cell's chemistry and clears the false "poor health" warning that appears after every cell swap on these platforms.
BIOS reporting battery health as poor immediately after replacement
The Latitude BIOS stores battery health data in EEPROM and compares the new cell's reported parameters against the degraded baseline from the old one. A freshly installed cell often reads as "unknown" or "poor" because the fuel gauge IC has not yet mapped the new cell's discharge curve. This is not a fault with the replacement cell — it is a calibration gap. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100%, and the BIOS will update its health assessment accordingly.
Laptop shuts down abruptly at 20–30% charge shown on screen
This happens when the fuel gauge IC's stored discharge curve no longer matches the actual voltage behaviour of the new cell under load. At full CPU plus display draw, the cell voltage drops faster than the uncalibrated gauge predicts, triggering an emergency shutdown before the displayed percentage reaches zero. The gauge needs at least two to three full discharge-charge cycles to re-learn the curve. After those cycles, run Dell's built-in battery diagnostics — accessible via F12 at boot — to confirm the gauge is tracking within normal range.