For those who still don't understand what I'm doing, or who think I'm taking a screwdriver to the system to make it do something illegal, here's a picture.
After midnight the battery, which was exported by about 11.30, charges back up to full. The house is running from the grid from 11.30 pm till 5.30 am. The battery is charges by about 3.30 am, and the hot water tank is heated from 4.30 am and is done before 5.30. At 5.30 I start to export the battery down to 30%. It has to be this early because the sun rises early on a sunny day. (By September I was exporting quite a lot later.) Solar generation started about 6 am, but solar plus the 3.5 kw battery export didn't reach the export cap of 5 kw. (If it had done, the system would have throttled the battery export to continue exporting the solar.)
The inverter is set at "export to 100%" from 7 am, which prevents the battery being charged from the solar, which is exported instead (although it continues to power the house of course.) At about 9.30 am the generation exceeds the allowed export, but instead of capping the generation, the system puts the excess into the battery. Things got a bit cloudier mid-afternoon but I put about 4 kwh into the battery that way before the sun dipped to the point where there was no more clipping, about 4 pm.
It looks as if I turned off the export setting around 3 pm to boil the kettle, although it seems I didn't need to, and didn't immediately turn it back on again, so the battery grabbed a bit more solar at that point. The system was set to turn the export off about 6 pm, to prevent the battery grabbing more solar than need be (if it did it would just be exported again, but there are losses in doing that). After that the house has full access to the battery and cooking and so on can be done without any concern about drawing mains power. You can see a spike of usage about 7 pm when I may have microwaved something.
Later, about nine, the house base load goes up, probably because I turned up the central heating and the boiler uses about 3-500 watts. It was April after all. The battery discharge steepens. Then, some time before 10.15 pm the battery starts to export what it has left, to be empty when the cheap rate starts, and the house can switch over to mains. The battery will fill itself starting at midnight.
It needs periodic tweaking as the sunrise/sunset times vary, and a decision whether to bother at all if the weather doesn't seem likely to be clear. But if it's set up right it can be more or less forgotten without risking more than a penny or two in mains consumption.
