About this replacement
Clevo M815P Series — 7.4V Li-ion Replacement Battery (6-87-M810S-4ZC)
This 7.4V, 3400mAh (25.16Wh) Li-ion cell replaces the original battery in the Clevo M815P, M810L, M815, and M810 notebook series. It matches the OEM voltage rail and connector pinout for those models. Install it in place of a degraded or failed original pack.
- M810 and M815 series compatibility: These models share the same two-cell 7.4V battery architecture, BMS handshake protocol, and physical connector. The 6-87-M810S-4ZC part number covers all variants in the cluster — including suffix revisions 4ZC1 and 4ZC2 — because the BMS firmware communicates identically across them.
- Bench tested on actual hardware: We ran this cell through full charge-discharge cycles on M810-series hardware. The BMS accepted the cell without fault codes, charge current tapered correctly at the top of the voltage curve, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
- First-cycle calibration on the M815P: After installing, run the laptop down to hibernate-cutoff under normal load — do not force-shutdown — then charge uninterrupted to 100%. This walks the fuel gauge IC through its learn cycle against the new cell's actual capacity curve and clears the inaccurate health warning the BIOS displays after every cell swap.
Why the M815P BIOS flags a new battery as poor health immediately after install
The Clevo BIOS reads health data from EEPROM registers inside the battery pack. When you install a new cell, those registers contain factory default values that do not match the BIOS's learned baseline from the old pack. The BIOS interprets the mismatch as degradation and throws a health warning. This is not a fault with the replacement cell. One full discharge-to-hibernate followed by an uninterrupted charge to 100% rewrites the learned data and clears the warning on next boot.
M815P shutting down unexpectedly at 20–30% shown on the gauge
This symptom happens when the fuel gauge IC has not yet calibrated against the new cell's actual discharge curve. The IC uses historical data from the old pack to predict remaining capacity, so it misjudges the voltage cliff on the new cell and triggers shutdown while the gauge still reads 20–30%. It is not a cell defect. Run two full discharge-to-hibernate and charge-to-100% cycles — by the second cycle the IC recalculates the curve and the gauge tracks accurately down to the real cutoff near 6.0V.