TALLINN, Nov 3 (Reuters) - Estonian energy storage technology maker Skeleton Technologies said on Tuesday it has raised 41.3 million euros ($48 million) from a group of investors in one of the largest cleantech investment rounds in Europe this year.

Tesla-rival Skeleton is the largest European manufacturer of ultracapacitor-based energy storage, the technology that enables the batteries of electric vehicles to fuel cars for longer.

"We are not competing with lithium-ion batteries and hydrogen fuel cells; we are complementary in improving performance and lowering cost," Chief Executive Taavi Madiberk said in an interview.

Last year, Tesla bought Skeleton's rival Maxwell Technologies Inc for $218 million, seeking to produce batteries that hold more energy and last longer.

Skeleton said all its earlier investors - EIT InnoEnergy, FirstFloor Capital, MM Grupp and Harju Elekter - participated in the round, which included also early investors in European payments firm Adyen NV.

Skeleton said its 2020 revenues were set to grow three-fold despite the COVID-19 pandemic. It did not reveal the number.

"Cleantech has become much more important," said Madiberk. "We have only scratched the surface. The momentum for energy transition and decarbonisation of the economy is stronger than ever." ($1 = 0.8593 euros) (Reporting by Tarmo Virki; Editing by Lincoln Feast.)