Varta, which has also been hit by a recent cyber attack, agreed a restructuring plan with majority shareholder Michael Tojner a year ago after key client Apple cut production of its AirPods headphones.

Under the plan Varta expected to return to "profitable growth" by the end of 2026, but late on Thursday it issued a statement saying that damage from the cyber attack, volatile customer orders, supply chain problems and a decline in demand for energy storage solutions have since cast doubt on its ability to meet that target.

Varta makes batteries for a range of uses including headphones. It received a 50 million euro ($53.37 million) cash injection from Tojner at the time of the restructuring agreement as well as an assurance from auditors KPMG that the firm had what Varta called "clear growth prospects."

"The big slowdown in the energy storage business is a negative surprise for me," said analyst Robert van der Horst of Warburg Research.

"Energy storage had always been held up as a growth area in the past year and more was invested into it even as capex was significantly reduced across the group as a whole," he added.

Varta made a loss for the first half of 2023 but recorded a profit for the third quarter.

In February this year it postponed the publication of its 2023 financial results following a cyber attack that halted production for weeks.

It is in the process of signing a standstill agreement with its creditors, it said in its statement.

Rothschild & Co has been mandated to explore recapitalisation options, it added.

($1 = 0.9369 euros)

(Additional Reporting by Alexander Huebner, editing by Andrey Sychev and Susan Fenton)

By Louis van Boxel-Woolf