Dell Precision 17 7770 Replacement Battery 11.55V 87.78Wh 5JMD8

Dell Precision 17 7770 / 7670 — 11.55V Li-Polymer Replacement Battery (5JMD8)

This 11.55V 7600mAh (87.78Wh) Li-Polymer battery replaces the internal cell in the Dell Precision 17 7770 and Precision 7670 Performance mobile workstations. It matches OEM part numbers 5JMD8, 965V4, and X9FTM. The connector, BMS handshake, and physical dimensions are direct matches to the factory unit.

• Precision 7770 and 7670 compatibility: Both models share the same 11.55V three-cell architecture, identical connector pinout, and the same BIOS battery authentication protocol — which is why a single cell covers both platforms without modification.
• Bench tested on actual hardware: We cycled this cell on a Precision 7770 and confirmed the BIOS accepted the BMS handshake, charge current stepped correctly through CC/CV phases, and protection circuits tripped at the expected low-voltage threshold.
• Post-install discharge cycle on the Precision 7770: After fitting, run one full discharge to hibernate cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears in Dell SupportAssist after every cell swap.

BIOS reporting poor battery health immediately after replacement

The Precision 7770 stores historical charge data in EEPROM on the old cell. When a new cell is fitted, the BIOS reads no prior cycle data and flags the battery as degraded or unknown. This is a data gap, not a fault with the replacement cell. Running one full discharge-to-hibernate followed by a complete charge gives the fuel gauge IC a full swing to calibrate against. After two to three cycles, the BIOS health status updates to normal.

Precision 7770 shutting down at 20–30% charge shown on screen

This happens when the fuel gauge IC still holds calibration data from the old, degraded cell. The percentage readout is calculated against the previous cell's characteristics, so it reads 25% while the actual cell voltage has already hit the BMS cutoff threshold. The laptop shuts down because the hardware voltage floor is reached before the OS percentage reaches zero. Force a full discharge to hibernate on the new cell, charge to 100%, and repeat once more — this realigns the fuel gauge IC to the new cell's actual voltage curve.