Here’s a very basic device handler for the Tesla Powerwall II
It will show you charge level and the current power for grid, site, solar and Powerwall.
It requires a FQDN for your Powerwall, because SmartThings is a PITA about allowing direct access via IP addresses unless you also write a device handler app - and I lost the will to live trying to decipher the awful documentation on doing this. Someone that knows what they are doing could probably sort this out really quickly.
The SmartApp simply sends you a push notification when the charge level goes through configurable upper or lower limits, with the simple purpose of alerting you when the battery is full so that you can turn something on to make use of excess solar. The SmartApp could be easily modified to switch a load on and off for you in response to charge levels.
Hope someone finds it useful.