Ercole Marelli began working at the age of 15 as an apprentice at a mechanical workshop. After a period in Paraguay, he returned to Italy in 1891 and founded a workshop of electrical appliances in Milan, where he manufactured batteries, accumulators and electro-medical devices. In December 1905, Marelli opened a plant in Sesto San Giovanni (Milan), the Ercole Marelli, which would obtain prominent exhibition space in the Galleria dell'Elettricita' in Turin 1911. This plant produced small electric motors, centrifugal pumps, and transformers.

In 1915, the "Società Anonima Ercole Marelli" was created, with the first Italian experiments in the fields of magnets, which were patented in 1917-18.

In 1919 Ercole Marelli created a new production department of automobile magnets, which later became in turn the company Magneti Marelli.