I am thinking the OP may have been reading this:
http://www.gizmag.com/tesla-home-battery/36276/
From the article:
"The same lithium-ion battery technology that powers Tesla’s electric vehicles will be used to develop a battery for the home, according to a statement by CEO Elon Musk during a recent conference call with analysts. The batteries would be used by homes and businesses to store excess energy generated from solar panels during the day, and drawn from at night when panels sit idle"
Intriguing possibiities for the RV industry.
If the system can run a house overnight, what could it do for an RV?