An external system monitors a rechargeable battery during charging without requiring a sensor to be built into or attached to the battery. A non-contact infrared array measures battery surface temperature, while an ambient sensor measures surrounding temperature. A controller analyses the readings against configurable alert criteria, activates local visual and audible warnings, and transmits temperature and status data online. A remote interface provides live readings, history, status and notifications, with separate live and archival data paths reducing display delay while retaining records.