Three fire engines and 16 firefighters attended the incident. Nobody was injured.
''Naturally, when a rocket company calls the fire service, they come prepared with a full response which meant several appliances attended,'' said Beck.
Firefighters remained on site for several hours to ensure the batteries were safely cooled.
Rocket Lab successfully reached orbit in January and details of its next flight will be made available in the next few weeks.
The battery incident happened a day after a group of United States Congress members visited the plant near Auckland Airport.
The company is registered in the US but has most of its operation in this country, including a launch range on the Mahia Peninsula.
Lithium batteries have caused problems before in aerospace. Soon after Dreamliners began flying commercially they were grounded after smouldering battery problems. They were resolved by more stringent controls over battery manufacturing, installing fire-roof housing and venting systems on planes.