Usage between grid and battery

I am finding it hard to understand the following
I have 2 9.5 batteries max output 2.6 kw.
On the half hourly chart I am getting results where the grid usage is higher than battery output but more important the total is lower than the 2.6 on the battery. I have instances where grid is 1.5 kw and the battery is 0.5 giving a total of 2kw usage. The battery system is topped up every night.
Any ideas or suggestions would be very much appreciated - I understand a few watts here and there

Quite possibly you ran a power load that exceeded the maximum instantaneous 2.6kW battery power output for a short or number of short periods of time over the 30 mins, which would have caused a draw from the grid.

You may also be confusing power and energy (kW vs kWh). I'm guessing the chart you are looking at says you consumed 2kWh of energy over a 30 min spell. Assuming you have a Gen1 inverter, limited to 2.6kW draw on the batteries, the max energy you can extract from the batteries over 30 mins is 1.3kWh (2.6kWh over an hour).

The Gen1 limited to 2.6kW draw from the batteries. Gen2s can draw 3.6kW from the batteries. As you mentioned 2.6, I'm assuming you have a Gen1.

You mentioned you consumed 2kWh in 30 mins (0.5kWh from the battery and 1.5kWh from the grid). As an example, this could have been achieved by ₂₀.86 mins at 0.3kW from the battery (with no grid draw) and ₉.13 mins at 2.6kW from the battery (with ₉.86kW draw from the grid). Examples that might cause this would large appliances - EV charge, an electric shower, oven, induction hob or combination thereof.

You can look at finer level details (roughly 5 min intervals) on the portal rather than the app to see peaks over these times.

Hope that helps.

4monks Thanks for that very helpful. The inverter is gen1