Trying to get that last 10%-15% to achieve a fully charged battery can take quite some time, which is why most will deplete their battery bank further before using their generator. Your batteries were nearly 90%, that is what most are trying to achieve when using their genny to restore consumed amphours. Running genny beyond that for just battery charging is, as you have indicated, somewhat fruitless. We have solar as well, but mother nature isn't always so accommodating when we RV off the power grid. On decent weather days we can run genny for about an hour in the morning to power our high current draw items and let solar complete the charging throughout the day.
