Battery-electric truck and SUV startup Rivian has added a third, large investor this year with a $350 million stake from Cox Automotive, the company announced today.

Earlier this year, Ford invested $500 million into the startup, and Amazon led an investment of $700 million.

Cox and Rivian will "explore partnership opportunities in digital retailing, service operations and logistics," according to a release.

"With the electrification of vehicles set to play a significant role in the new mobility future, this partnership opens another channel of discovery and learning for Cox Automotive,” said Joe George, president of Cox Automotive Mobility Group. "Advancements in battery technology and the electrification of fleets are two of our primary focus areas, and we believe this relationship will prove to be mutually beneficial."

Rivian is developing several EVs including its R1T pickup and R1S midsize SUV that will both be built on the company's skateboard platform. The vehicles will be able to provide up to 400 miles of range and have off-road capability.

Cox Automotive plans to use the investment as an opportunity to learn more about EV batteries and their potential replacement in vehicles, said Chintan Talati, a company spokesperson.

"We're excited to partner with all of our OEM partners to better understand batteries throughout their life, from their first through final life stages," Talati said.

Rivian remains an independent company, and will add a Cox Automotive representative to its board.

"We are building a Rivian ownership experience that matches the care and consideration that go into our vehicles,” said RJ Scaringe, founder and CEO of Rivian. "As part of this, we are excited to work with Cox Automotive in delivering a consistent customer experience across our various touchpoints. Cox Automotive’s global footprint, service and logistics capabilities, and retail technology platform make them a great partner for us."