Twenty-five fire trucks and support units responded to the fourth alarm blaze in Carrington Street, just after 7pm.
Nearby streets were blocked off as firefighters attacked the flames, which had taken hold in the roof, causing thick, black smoke to billow from the single-level factory.
More than 50 firefighters contained the fire within half-an-hour and extinguished it just after 10.30.
A third of the 600sqm brick and fibro property was destroyed in the incident.
FRNSW investigators inspected the site overnight and are pointing to damaged lithium cells as the likely cause.
