A problem with keeping lithium batteries outside is that it gets way, way too cold in many parts of the world for them to survive charge cycling.
I mean: Sure, there's ways to improve that. There's even climate-controlled outdoor racks, and rack-mount batteries from vendors like EG4 to slot into them.
But a common goal of home battery arrays is to improve the energy efficiency of that home. Heating (or, I suppose in extreme cases, perhaps even cooling) a battery box runs counter to that goal.
I mean: Sure, there's ways to improve that. There's even climate-controlled outdoor racks, and rack-mount batteries from vendors like EG4 to slot into them.
But a common goal of home battery arrays is to improve the energy efficiency of that home. Heating (or, I suppose in extreme cases, perhaps even cooling) a battery box runs counter to that goal.