While this article focuses on integrated systems that include inverter/chargers, PV controllers, integration panels, and monitoring and control software, as well as some new lithium-ion–based storage systems, integrators have historically used BOS components from a wide array of vendors for energy storage applications. MidNite Solar offers an extensive line of high-voltage MPPT charge controllers, inverter integration panels, battery enclosures and rapid-shutdown equipment that can help you solve energy storage system integration challenges. Morningstar provides MPPT controllers specifically designed for retrofitting grid-direct systems with battery backup. Iron Edison has reintroduced nickel-iron batteries to the market, as well as adding new lithium-iron models. And while the industry appears to be on the cusp of a transition to lithium-ion batteries for some grid-tied applications, such as daily cycling, VRLA type batteries from manufacturers including Concorde Battery, Deka Solar, MK Battery, Trojan Battery and U.S. Battery are still mainstays for grid-tied energy storage systems.