Sizing DC system components: there´s usually something missing

The design of DC systems is typically based on a few calculations that support the procurement of a battery, battery charger, and DC distribution panels. However, DC systems are normally used to power the most critical functions in a facility and therefore these systems warrant considerably more attention. The DC system is of little value if it does not supply the power needed at a time of crisis. One of the biggest assumptions of the traditional design calculations is that a chosen minimum battery voltage used in the battery sizing calculation will supply adequate voltage to each of the DC system loads, including both major equipment and components within control circuits. Since the loads on a typical DC system will have different requirements for operating voltage and will be connected by various sizes and lengths of cables, it is relatively easy to create a situation where the original assumption of delivering adequate voltage will be violated. This paper addresses how to ensure that the important consideration of load terminal voltage is properly evaluated as well as how to avoid some of the other more common mistakes in DC system design