Tesla powerwalls are currently supported only in a custom integration but Tesla has changed their API model to exclude end users in favor of a fleet model which breaks the custom integration. Tessie is built to use the fleet API and currently the integration works very nicely for Tesla vehicles only. Tessie is in the process of making Powerwall integration available as part of their service. It would of tremendous benefit to all Tesla powerwall owners to extend the HA Tessie integration to add Powerwall support to the vehicle support that is already there.
You forgot to vote 
Doh! Thanks for the reminder. First time posting.