The UAW says that most of the workers at the Ford joint-venture battery plant have signed union cards

The United Auto Workers said on Wednesday that most of the workers at a Ford Motor (F.N) opens new tab joint-venture battery plant in Kentucky have signed cards to show their support for the union.

The Blue Oval SK company is run by SK On and Ford, a partnership from South Korea. It is the latest battleground for the union as it tries to get more people to join.

In the beginning of the year, the UAW spent $40 million to unite non-union cars across the United States. Tesla (TSLA.O) and Toyota (7203.T) were among the companies that helped with this effort.

The UAW said that in support of the union, a “supermajority” of workers at the Ford Kentucky battery plant had signed union cards. It didn’t say what amount it was.

Since he led a six-week strike against the Detroit Three last fall, UAW President Shawn Fain has had his sights set on battery plants owned by Ford and General Motors (GM.N). He wants workers at EV-related plants to be union members just like workers at gasoline-engine plants.

Jim Farley, the CEO of Ford at the time, said that Fain was “holding the deal hostage over battery plants.”

Representatives for Ford and Blue Oval SK did not answer when asked for a statement.

Fain has said that organizing these battery and EV factories into unions is important for the UAW’s future success, especially since the number of its members is decreasing.

Ultium Cells, a joint venture between GM and LG Energy Solution (373220.KS), starts new tab at plants in Ohio and Tennessee. This is another win for the union. At a GM battery plant in Ohio, the union and the company came to an agreement in June. In September, GM decided to recognize the union at an Ultium plant in Tennessee.

Workers at Ford’s battery hub in Kentucky will have an official vote on whether to join the union if the process goes on as planned.

Based on the current deal with Ford, if the UAW wins, workers will start making more than $42 an hour after three years. Their starting pay will go up from $21 an hour to $26.32 an hour, the union said.