Shown here is the layout of a battery storage system which can be found in Photovoltaic or electric vehicle charging applications. For this system, DC power relays are used for safety cut-off in the event of a defect in or malfunction of the battery system during the charging and discharging process. For large inverters, there is always a smoothing capacitor on the input side to prevent voltage fluctuations if a large load is connected to the AC side. Due to the size of this capacitor, there is a lot of inrush current generated that can cause contact welding. Thus, a good design will make use of a pre-charge relay in series with a current limiting resistor that can be used to absorb this inrush before the main power relays are turned on.