When the inverter boots up for the first time, is it normal that it injects power from the batteries to the grid?

It’s normal operation. During initialisation Imeon performs phase verification procedure to check if its phase No. 1 of the AC Grid Connector input corresponds to phase No. 1 connected to the Smart Meter. In order to do this, during 30s Imeon injects 2kW to one phase after another, and cross-checks it with the response detected by the SmartMeter. This is done to make sure that all phases are correctly identified, at the SmartMeter and Imeon inputs.