About this replacement
HP EliteBook 820 G3 / 725 G3 — 11.4V Li-Polymer Replacement Battery (SN03XL)
This is an 11.4V, 3700mAh (42.18Wh) Li-Polymer replacement battery for the HP EliteBook 820 G3 and EliteBook 725 G3. It slots directly into the internal bay and connects to the same BMS handshake points as the original SN03XL cell. Use it when the original battery no longer holds charge through a standard workday away from the mains.
- EliteBook 820 G3 and 725 G3 platform fit: Both models run the same 11.4V three-cell battery rail with identical connector pinout and BMS communication protocol — that is why one cell covers the full series, including the T9X45EA and X5N60UC variants.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an EliteBook 820 G3 unit, confirming the BMS handshake authenticated correctly, charge current ramped normally from CC to CV phase, and the protection circuit tripped at the expected low-voltage cutoff threshold.
- EliteBook BIOS learn cycle after swap: After fitting this cell, run the laptop down to hibernate-cutoff on battery alone, then charge uninterrupted to 100% without using the machine. This resets the BIOS battery learn cycle and clears the inaccurate health warning the firmware displays after every cell replacement.
BIOS reporting poor battery health immediately after installing a new cell
HP's BIOS reads health data from the battery's EEPROM and compares it against the charge history stored from the previous cell. A brand-new cell has a different EEPROM state, so the firmware flags it as degraded before any calibration data exists. This is not a fault with the replacement cell. Running one full discharge-to-hibernate followed by an uninterrupted full charge gives the BIOS enough data to update its health register. After that cycle, most units clear the warning and report normal status.
Laptop shuts down abruptly while the OS gauge still shows 20–30% remaining
This happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The IC is still referencing the old cell's voltage-to-capacity mapping, so it misjudges the remaining charge at high load. When the CPU and display draw full current together, the cell voltage drops below the BMS cutoff threshold before the gauge reaches 0%. Run two to three full discharge-to-hibernate cycles, charging to 100% each time, to let the fuel gauge IC re-map against the new cell. After calibration, the shutdown floor should align accurately with the displayed percentage.