chris_m
What I do is just export the battery for 2 hours between 5 and 7pm. Using a 8.2GB battery this exports about 60% of the battery, from 100% it leaves a little over 40% for evening use. You can experiment this way until you get what you need.
The battery level setting tells the software what level the battery has to be at to start the export. I have mine set to 95 which means if the battery is below 95%, it won't export. It's always 100% though at this time of year so NP.
I have temp set at 1 so it always works no matter what the weather. After 7pm there's not much sunlight anyway so it's not important.
Hope all this makes sense.