System76 Lemur Pro(10) Compatible Battery 7.7V 4650mAh

System76 Lemur Pro (lemp9 / lemp10) — 7.7V Li-Polymer Replacement Battery

This 7.7V, 4650mAh (35.81Wh) lithium-polymer cell replaces the original battery in the System76 Lemur Pro 9th and 10th generation laptops. Both generations share the same battery bay dimensions, connector pinout, and BMS communication protocol. If your Lemur Pro no longer holds a charge or powers off unexpectedly, this cell restores the original pack specification.

• Lemur Pro 9 and 10 compatibility: Both lemp9 and lemp10 use the same 249.60 × 49.10 × 5.00mm cell with an identical connector and fuel gauge IC interface. The coreboot firmware on both generations communicates with the embedded controller over the same charge path — no hardware modification needed between the two models.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a lemp10 unit. The embedded controller accepted the cell without fault codes, the charge path activated normally, and the BMS reported cell voltage within the expected 4.2V per-cell ceiling at full charge.
• Post-install discharge cycle on the Lemur Pro: After fitting this cell, run the laptop off battery until coreboot triggers the low-power hibernate threshold — then charge uninterrupted to 100%. The Lemur Pro's embedded controller uses this full cycle to reset its battery learn table. Skipping it leaves the fuel gauge reporting inaccurate state-of-charge for weeks.

Why coreboot reports poor battery health immediately after a Lemur Pro cell swap

The Lemur Pro runs coreboot with an open-source embedded controller firmware. When a new cell is installed, the EC carries over health and cycle-count data stored from the previous pack — it does not auto-reset on cell change. Until a full discharge-to-hibernate and uninterrupted recharge cycle is completed, the EC has no real baseline for the new cell's capacity curve. System76's own documentation refers to this as the battery learn cycle. After one full cycle, the health percentage recalculates against the new cell and the warning clears.

Lemur Pro shutting down at 20–25% state-of-charge shown on screen

This is a voltage cliff issue, not a calibration problem. Under combined CPU and display load, the degraded or uncalibrated cell drops below the EC's minimum sustain voltage before the fuel gauge reaches 0%. The EC interprets the sudden voltage drop as an emergency cutoff and shuts down immediately. The fix is the same full discharge-to-hibernate cycle — once the EC maps the new cell's actual discharge curve, the state-of-charge reading and the physical voltage floor align. After calibration, confirm the EC reads above 3.0V per cell at the point where shutdown previously occurred.