KACO Blueplanet Gridsave92 is implemented as a SymmetricEss, because it only allows setting a ‘Sum’ power and not individual phases.
In your case you don’t actually have to implement an ESS, but rather a Battery and combine it with a ESS Generic Managed Symmetric and Battery-Inverter KACO blueplanet gridsave.
You only need to implement a Battery Component for your custom battery.