60% discharge between 1115hrs & 1155hrs

Evening,
Apologies, I am new to this battery interface / charging etc.
A strange thing happened today whilst I was out, between 1115hrs (80%) & 1155hrs then 20% the GivEnergy 9.5kWh battery suddenly discharged. Looking at the App it states the battery use for today was 3.5kWh to my house. I have a 3.6 kWh inverter
May I ask if anyone knows what this anomaly could be please?
It’s due to charge between 0030-0530hrs so I’m hoping it will charge and hold it.
I have checked the notification area of the App & there hasn’t been any firmware updates or messages saying the battery was calibrated.
Thanking you in anticipation …
Rossy

Reports of sudden drops in SoC are quite common here.
Do you regularly charge to 100% and/or discharge to empty (and allow to idle). There's a video on the GE YouTube channel recommending this, and it seems to allow the BMS to align its model of the SoC.

DD DD, yes I charge in silent hours to 100% & the battery then discharges for house demand, the solar array charges battery during the day

Rossy does it fully discharge too? It probably needs to visit both ends regularly. And it may be only at the low end that it does cell rebalancing.

DD DD thank you, generally my usage of the 9.5kWh battery leaves me between 10-25% in reserve. To be honest this is the first time in months that it has discharged (to 4% the minimum).
I have just reset the inverter to factory default then completed the timed charge & eco settings (so solar & battery provide power to house).
I’ll see if it charges overnight via Octopus & see if battery holds charge tomorrow.
It was just strange how it discharged from 80% to 20% during the 40 minutes !😳 I wasn’t even at home & there’s no demand from home either 🤔

Rossy It (probably) didn't actually discharge as such. The BMS is rather poor at tracking the true SoC of the battery. (Voltage curve of LFP is very flat, so can't infer stored energy from voltage.) What we believe happened is that the BMS suddenly realised that it had overestimated how much energy was stored, and was correcting itself. So the energy was never actually there.

If you have spare battery at the end of the day, exporting it back to the grid can be slightly profitable, if you can earn 15p for export then re-import at 8p overnight. And the battery would probably benefit from being fully run down from time to time - lets the BMS correct its SoC tracking.

Rossy It was just strange how it discharged from 80% to 20% during the 40 minutes !😳 I wasn’t even at home & there’s no demand from home either 🤔

It probably didn’t discharge to the home that amout of energy (you can look in the portal and see how much home load there was in that time period).

What happened is that the battery suddenly realised that it didn’t have as much charge as it thought it had and corrected its SoC % figure. Best practice as other have said is to periodically fully charge and fully discharge the battery, this helps to avoid such corrections. Doesn’t have to be every day but regular enough

geoffreycoan Thank you for your advice & help Geoff.
My load between those times was only 503W as I was out. I will see how things apn out overnight & tomorrow morning (fingers crossed) ..

During the summer my battery was charged to 100% by the mains or by solar and never ran out. The first day it did I got a big drop in charge, 30% IIRC Now it goes from 100% down to 4% everyday it behaves itself.

I would guess it's a SoC correction. BMS suddenly reaslised it had got out of step with the battery due to going beyond where it normally discharges too and the voltage dropping off quicker than expected.