There's a mentioning of this in the manual in the Photovoltaic Systems: Component-based Models section:
"The current version of the software includes simple models of loads and storage for gridconnected
systems with electric storage batteries."
Update October 26, 2015: SAM's detailed photovoltaic model does now support battery storage. For an introductory video, see sam.nrel.gov/node/69635
.
Dear David,
The current version of SAM does not model electric storage for PV systems. My apologies for the error in the documentation. That is left over from an older version of SAM.
Best regards,