The Tesla 3 battery has bms as part of the penthouse. As well as a charger and dc-dc converter. You will need a controller for the battery pack. Ingenix is the source. Openinverter has boards for the Tesla 3 charger and bms. Not sure whether they have a product to control the contactors. EVTV also has a controller but last I knew you had to buy the battery from them as well.