FnS' off-grid energy storage system has been specially developed for the production and storage energy for residential or microgrid applications. Which combined with PV modules, inverter, MPPT charger, CPU, and lithium battery, can store and provide power to home appliances. These series have four options that can choose from 2kW to 6kW, the integrated MPPT search maximum power circuit by voltage and current of the PV module, to provide the maximizing energy delivered. And the independent modularization design improves the reliability and extendibility greatly. The pure since wave can provide stable powers for home electronics with low loss, high conversion efficiency. The multiple functions like strong shockproof, solar/grid/ battery complementary, automatic battery charging & monitoring, auto-selection mode, AVR functions, etc., which can meet different customer’s demands on various applications.