MUNICH (Reuters) - Shares in Varta plunged on Monday after the German battery maker said restructuring options to avert insolvency would leave equity investors with nothing.

The stock was down 80% after the open on Monday at a record low, following a statement on Sunday that two remaining turnaround proposals would result in a delisting, with existing shareholders, except Austrian majority owner Michael Tojner, not receiving any compensation.

"In addition, a significant debt haircut is planned for certain creditor groups and the deferral of remaining claims," Varta said.

Potential new investors, among them Tojner and Sportscar maker Porsche, would inject capital under one of the scenarios, it added.

Varta said it had decided to notify the relevant courts of an overhaul in accordance with Germany's corporate stabilisation and restructuring act, adding that without such a move the firm would have to incur losses that would consume its share capital.

Varta, which has a market value of 440 million euros ($479 million), said earlier this month it was in talks with Porsche over a potential investment that could result in the carmaker becoming a majority owner of Varta's V4Drive business.

Sunday's statement, meanwhile, could see Porsche take a direct stake in Varta itself.

Porsche said it could confirm that it was in negotiations with a view to acquire a majority stake in V4Drive via a possible capital increase.

"The prerequisite for this is a sound financial basis for Varta AG. Under certain circumstances, we could therefore imagine participating in a financial restructuring of Varta AG as a whole. Discussions on this are still ongoing," Porsche said in a statement.

Varta said in April it might not meet targets set under its restructuring plan and was exploring recapitalisation options that should help it return to "profitable growth" by the end of 2026.

Varta said it hoped to quickly decide on one of the two scenarios, adding it needed debt capital or a combination of debt and equity in a "high double-digit" million euro amount.

It said it was unlikely that either proposal would garner the necessary majority at a general meeting of shareholders, adding the proposed restructuring, if accepted by courts, would allow it to realise this without investor approval.

($1 = 0.9194 euros)

(Additional reporting by Ludwig Burger; Editing by Frances Kerry, Susan Fenton and Louise Heavens)