What the 1-cell fuel gauge does on your board
The BQ27500DRZR: It monitors one series cell — the number of cells is fixed at 1, so this part fits a single Li-Ion or Li-Po pack, not a multi-cell stack.
The base product number BQ27500DRZR shares the same die and firmware across package variants; the DRZR suffix identifies the 12-VFDFN reel.
Protection and temperature monitoring
The IC includes over-temperature fault protection — it flags or shuts down when the internal die temperature exceeds the safe threshold, protecting the pack during charging or heavy discharge.