Tesla could be planning to build more than just vehicles at its $1 billion assembly plant in southeastern Travis County.The electric vehicle manufacturer has plans to produce battery cells at the site, according to documents filed with the state. The company has already said it will produce its Cybertruck, Semi, Model 3 compact sedan and Model Y vehicles at the plant.Telsa has started construction on the Travis County site, and the company has begun hiring in Central Texas. Currently, Tesla’s job site lists more than 80 open positions in Austin.If a battery facility is added to the...… Tesla could be planning to build more than just vehicles at its $1 billion assembly plant in southeastern Travis County.The electric vehicle manufacturer has plans to produce battery cells at the site, according to documents filed with the state. The company has already said it will produce its Cybertruck, Semi, Model 3 compact sedan and Model Y vehicles at the plant.Telsa has started construction on the Travis County site, and the company has begun hiring in Central Texas. Currently, Tesla’s job site lists more than 80 open positions in Austin.If a battery facility is added to the...WW…