The behavior of solar + PW is not quite what you described, and it does make sense once you work through the options. When there is an outage, the solar array cannot generate more than can be consumed. (This is also true when the grid is up, but the grid is effectively an infinite sink for purposes of residential solar power generation.) In an outage, the solar can be used either to run the home or to charge the PWs. If the PWs are full and the home load is less than the incoming solar, this will quickly become dangerous. So, one of two things happens. For older installs, the solar is shutoff completely, and the PWs run the home. For some newer installs, the systems are capable of curtailing the solar to match the home load. In the former case, this behavior only persists until the PWs are drained to a level where solar can resume. (In my case, it shuts off around 97-98% and comes back in the 92-95% range - it likely checks about every 5 minutes to see if the PWs have room for more energy.) In the latter case, the PWs should generally remain in that 97-98% range.
In either case, your system will attempt to maintain near-full batteries whenever possible (solar generation exceeds home load) but will curtail or cycle off the solar as a safety measure whenever the PWs get too full. All you lose out on in an outage is the benefits of net metering/load shifting since the grid is not available for that purpose.
