There are a number of companies that sell excellent UL-listed batteries and battery subsystems. But these systems won't work as expected without an inverter, communications, software and supporting electrical equipment (not to mention a qualified contractor to install and maintain them).
Moreover, these components must be tightly integrated, ideally by the inverter manufacturer. It is virtually impossible for a contractor to install a code-compliant battery storage system unless there is thorough integration between the battery subsystem, the inverter, and the software that makes it all work together.
As a result, manufacturers that provide (or control) both the inverter and battery have an advantage when it comes to installation and operation simplicity.
Whatever your storage need we can help.
Ainfo [at] wcelectric [dot] ca x204-475-4796