Sudden SOC drop

This morning:

On 3013

I am aware of this phenomenon but what I don't understand is where does the electricity go ?!

Are the batteries really full or does the inverter just think they are, and then change its mind?

Its the battery management system rather than the inverter which gets "confused". Basically the battery tends to over-estimate the charge level and it progressively gets worse until a sudden correction happens.

I got a 20% drop to zero last night, battery hadn't been below 35-40% for a while so not entirely surprised. Full charge cycle took 10.4kWh (on negative rates from Octopus) which sounds about right to me so I doubt I'll see any more SoC corrections for a while - last one was a couple of months ago.

Vestas Thanks for that

Our batteries do get to do a full cycle every 24 hours at the moment - fill up overnight, use during the day to supplement solar.