About this replacement
Dell Latitude 5320 / 7320 / 7420 / 7520 — 15.2V Li-Polymer Replacement Battery (7FMXV)
This is a 15.2V, 3800mAh (57.76Wh) Li-Polymer battery for the Dell Latitude 5320, 7320, 7420, and 7520 series laptops. It replaces OEM part number 7FMXV and fits directly into the same bay with the same connector orientation. Capacity figures are from the product specification — not extrapolated from web sources.
- Latitude 5320 / 7320 / 7420 / 7520 shared platform: These four Latitude lines run the same 15.2V four-cell battery architecture and share an identical connector and BMS handshake protocol. A single cell revision covers all four because Dell used the same power board across this generation.
- Bench tested on actual hardware: We cycled this cell on a Latitude 7420 and monitored BMS communication throughout. The protection circuit responded correctly to charge cutoff, over-discharge, and temperature thresholds — no fault codes triggered during either charge or discharge.
- Post-install calibration for Latitude firmware: After fitting this battery, run the laptop down to hibernate cutoff without interruption, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears in Dell Power Manager after every cell swap.
BIOS reporting battery health as poor immediately after replacement
Dell's BIOS stores capacity and cycle data in an EEPROM on the battery controller. When a new cell is installed, the BIOS compares the fresh EEPROM state against accumulated cycle history from the previous battery and flags a mismatch as poor health. This is a firmware read issue — not a fault with the replacement cell. Run one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100% to allow the BIOS learn cycle to reset against the new cell's actual capacity. After two to three cycles, the health indicator in Dell Power Manager should update to normal.
Laptop shutting down at 20–30% charge shown on screen
This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The gauge is still mapping discharge rate to the old cell's characteristics, so it reads remaining capacity accurately at rest but underestimates how fast voltage drops under full CPU and display load. The actual cell hits its low-voltage cutoff before the gauge reaches 0%, which causes an abrupt shutdown. Run two to three full discharge-to-hibernate cycles without interrupting the drain — this gives the fuel gauge IC enough data points to recalibrate. After calibration, shutdowns at 20–30% should stop; if the cell voltage at cutoff is still reading above 14.0V on a meter, the gauge is still mid-calibration.