Typically, in a non-grid tie system, the battery charging system would be run from the same 120/240 AC inverter that runs the household loads. The charging system would be treated as nothing more than another load for the inverter to service.
Here's the logic:
Given the mis-match between the voltages required for charging batteries and the solar module DC output voltages, it is more efficient to run the battery charging system from the AC inverter, rather than through a direct connection between the solar module DC output and the batteries. This is especially true when considering the variability of the solar module output voltage as a function of input irradiance.
--Boot Hill
I hadn't considered that because I assumed that the photoelectric effect in the cell would produce constant voltage and variable current, quanta being what they are.
What is the typical means by which the system supplies a constant output voltage, or does it? If it does, what is they allowed RMS variation in that output voltage?