Givenergy battery rapidly discharging

It's happened twice now!
I have 2 x 9.5KW GE batteries and I've experienced rapid discharge on a couple of occasions. The first was in the middle of the night with no significant demand. It didn't discharge to the house or the grid but just went flat.
The 2nd time was tonight while exporting to the grid. Both batteries almost t 100% before the export and over the 3 hr period should have exported a maximum of 10.8Kw, leaving approx 40%ish for the rest of the night. Before the 3 hours were complete they fell rapidly from 50% to 4% over just a few minutes.

Any ideas?

Eco-Me It sounds very much like a SoC correction which is where your inverter realises that its idea of what the battery SoC is is wrong. There's lots of threads and discussions about this on the forum and is something GivEnergy have tried to fix in progressive firmware and BMS updates

What firmware and BMS do you have in your GivEnergy inverter and batteries? An upgrade may help resolve this

The other advice is to ensure that you regularly (say weekly) allow the batteries to fully discharge to empty, rest a bit, and then fully charge. If they are maintained in a semi-full state for long periods of time then this is when the SoC corrections are more likely to occur

HI Geoffrey,
Thanks for the rapid reply.
My batteries have been in a state of semi charge for a while, so this could be the issue,
The inverter firmware version is D0.309-A0.309 and the battery firmware 3017. It doesn't show that any updates are available.
Thee batteries are currently completely flat set to charge on the cheap rate between 02:00-05:00 tomorrow. This will only take them to 50%. Would you recommend extending the charge to get them completely topped up or wait for the sun to shine?

Eco-Me charging from solar is fine, save your money, but it is worth ensuring the batteries get "exercised" over a full charge range reasonably regularly, so an overnight charge and solar will do just fine to fill them up

If you look at the givenergy channel on youtube there is a video recently (couple of months) ago about this.

And try to let them drain down to empty periodically