Since we are a tesla and bolt house, I want to share the 50amp circuit in the garage with a siemens versicharge and a tesla HPWC. The Siemens Versicharge has a logic level input on a small terminal block that is used to stop it from charging gracefully. So I found a current sense relay that will sense current from the wife's tesla EVSE and stop the versicharge from charging. I wasn't worried about balancing the current between the two units... I'm just fine as long as only one of them can charge at a time. This little relay works perfectly with the terminal strip input on the versicharge unit and fits neatly in the subpanel in the garage.
With this, the tesla can charge at 40amps and the bolt can charge at 32amps. If the tesla starts to pull more than 8-10amps (adjustable), the bolt will stop charging.
https://www.amazon.com/gp/product/B00I9IFJOM/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
With this, the tesla can charge at 40amps and the bolt can charge at 32amps. If the tesla starts to pull more than 8-10amps (adjustable), the bolt will stop charging.
https://www.amazon.com/gp/product/B00I9IFJOM/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1