The GNB Industrial Battery Co. SMPS 48/15A Electric Car Charger is a high‑power DC charger that uses a microprocessor‑controlled ferro‑resonant topology for fast, fully automatic lead‑acid charging. Known failure modes include the F4 HIGH fault (battery voltage >2.40 V/C at startup) caused by incorrect voltage jumper settings or using an oversized battery, as well as component degradation in the power stage such as MOSFETs and capacitors under prolonged high current operation. First‑check diagnostics: verify that the input 48 V supply is within spec and stable; inspect the voltage jumper configuration against the charger’s wiring diagram; perform a visual inspection of the output rectifier, filter capacitors, and any heat‑stressed components for signs of damage or failure.[oss-gpt-20b]