The PV contractor I work with is installing a system that has a Fortress Evolt 18.5 battery which is the size of a dishwasher and has been installed under the inverter inside a garage. It comes with a prewired plug and cord that connects it to the inverter. There is no ground wire in this cord. The unit has a screw marked with a grounding symbol on the outside of it's case near the floor. What is the proper way to ground this? It's a small screw. It could maybe handle a #10. What size ground is required? The cord has 4/0 conductors. I can post pictures if needed.