Hasee K780S-i7 Replacement Battery 14.8V 5200mAh

Hasee K780S-i7 / K780E — 14.8V Li-ion Replacement Battery

This is a 14.8V, 5200mAh (76.96Wh) Li-ion battery for the Hasee K780S-i7 and K780E laptops. It replaces the original cell pack when the factory battery degrades or no longer holds a usable charge. Voltage and connector match the stock unit directly.

• K780S-i7 and K780E compatibility: Both models run the same 14.8V four-cell battery architecture with an identical connector pinout and BMS handshake protocol. Swapping between the two variants does not require a different cell — the power management IC reads the same charge profile on either board.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on the K780 platform and confirmed the BMS communicates charge state correctly to the host board. The protection circuit triggered at the expected low-voltage cutoff without tripping prematurely under CPU and display load.
• First-cycle calibration after install: After fitting this battery, run the laptop down to hibernate cutoff on battery power alone — no sleep, no lid close — then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after a cell swap.

BIOS reporting poor battery health after fitting a new cell

The K780 BIOS reads charge-cycle count and health data stored in the old cell's EEPROM. When a new cell is fitted, that EEPROM data resets, and the BIOS flags the mismatch as degraded health — even though the new cell is fully functional. This is not a fault with the replacement. One complete discharge-to-hibernate followed by an uninterrupted full charge gives the fuel gauge IC enough data to re-establish an accurate baseline. After two or three cycles, the health indicator corrects itself.

Laptop cuts out at 20–30% charge shown on the gauge

This happens when the fuel gauge IC has not yet calibrated against the new cell's actual voltage curve. The gauge predicts 20–30% remaining, but the cell voltage drops below the BMS cutoff threshold sooner than the uncalibrated model expects — causing an abrupt shutdown with charge still displayed. The fix is a deliberate full discharge cycle: run every load you can (display at full brightness, active CPU task) until the laptop hibernates on its own. After that discharge, charge to 100% without interruption. The gauge recalibrates against real voltage data and the premature shutdowns stop.