We just acquired three Styleview powered carts and they do not have the RUI as is shown in the documentation. They do have a battery monitor on a lower front panel. At this point they only run under external power and do not switch to inverter even with a known good (and fully charged) battery. I'm wondering if the RUI is required to turn on the inverter or if somehow the system can run without it? Also if the RUI is needed are those available from Ergotron?