The Nissan Leaf electric car doesn’t compete directly with any of the luxury models from Tesla Motors, but Nissan is now targeting Tesla in a different arena. The Japanese carmaker will offer standalone battery packs for home energy storage. Available for pre-order in September, the xStorage line of battery packs was developed in concert with power-management company Eaton. DON’T MISS: Tesla Didn’t Invent Home Energy Storage, Has Many Competitors (May 2015) In Europe—where the packs…