Can I encourage predbat to charge as late as possible when solar isn't meeting forecast?

[NotFred07]

tl;dr - Can I encourage predbat to only charge at the last minute before a rate change, rather than keeping the battery at the SOC level it would like during the day even if solar isn't generating what it would expect?

I'm on Octopus Flux, so have cheap overnight import, middling day import, then expensive evening import, with a similar export profile. Every day the plan appears to be - charge the battery overnight to the minimum needed to both prevent import during the morning, and also mean that solar gets the battery to 100% at the start of peak time. Then dump the battery back to the grid to hit minimums at the end of peak, and run on grid through the evening (peak export is more than evening import). All of that makes perfect sense and is a very good plan.

The issues come as the day goes on. My solar seems to be lumpier than predbat predicts, and is often lower during the day then picks up later, with overall generation still being more or less on target. The issue is that as the battery SOC falls behind where predbat would like it to be, it tops it up from the grid immediately to keep it on track. If the sun then comes out later, I end up exporting again at the day rate.

In an ideal world, when solar hasn't met expectations predbat would only start charging at the last moment it can in order to hit the 100% SOC by peak time. This would give maximum opportunity for the solar to catch up. Is there a way to encourage it to do this?

So far I've played with making the solar and load modelling more pessimistic, to only mixed effect. This makes it charge more overnight as you'd expect, but it is then pessimistic during the day as well so still charges a bit at day rate, then hits 100% long before the peak window. So I don't think this is the right approach.

A couple of examples below. The first is the plan for a day ahead, everything looks perfect. The second is what has actually happened so far today, showing the additional bits of charging which didn't turn out to be needed (it's a mild example today, on other days it's been higher but they have fallen out of my history now).

[gcoan]

My solar seems to be lumpier than predbat predicts, and is often lower during the day then picks up later, with overall generation still being more or less on target. The issue is that as the battery SOC falls behind where predbat would like it to be, it tops it up from the grid immediately to keep it on track

The first bit you need to get right is your solar forecast because without that Predbat is going to struggle for you.

Do you have shading on your panels in the morning maybe? Check you have configured your solar forecast correctly, in particular the array orientation (read the forecast documentation because Solcast in particular uses Southern hemisphere approach to orientation), the angle and array size. Possibly tweak your panel size or efficiency down a bit, I had to do this with mine to get a better fit.
If you are using the bjreplay solcast integration you can turn on auto dampening for Solcast to adjust your forecast based on historical actuals.
Predbat has a similar approach with PV Calibration but the Solcast model is better. If you do use Solcast dampening then turn off Predbat PV calibration.

Second lever you can tweak is to increase the metric 10 PV weighting so Predbat is more pessimistic about your overall forecast.

You saying that Predbat charges when SoC goes below what Predbat likes, suggests you have set a min soc level. Generally best not to do this becase Predbat will charge to preserve the battery almost regardless of rate. Its better to let Predbat not be constrained by a min soc, it will then be less succeptible to charging unnecessarily