Series and parallel connections are simple to define in electrical terms, but underlying these basic concepts is a wealth of detail. The battery voltage determines the number of series connections and can have a significant effect on battery safety and reliability. | Parallel and Series Connections J McDowall Saft America Inc. North Haven CT USA 2009 Elsevier . All rights reserved. Introduction Series and parallel connections are simple to define in electrical terms but underlying these basic concepts is a wealth of detail. The battery voltage determines the number of series connections and can have a significant effect on battery safety and reliability. Paralleling is used to increase system capacity and to add redundancy but there are many pitfalls in designing a paralleled battery system. Adding to the confusion is the fact that a number of myths concerning paralleling have assumed common wisdom status in the battery industry. This article discusses these issues provides some basic insights into statistical battery reliability and describes the way in which these concepts are likely to evolve with the emergence of advanced battery technologies such as lithium ion. Basic Concepts Cells Strings and Batteries The terms cell string and battery are used throughout this article. In this context the cell is the basic electrochemical unit containing the electrodes and electrolyte a string is a grouping of interconnected cells with the same nominal voltage as the direct current DC system and a battery is the overall assembly of one or more strings. Although in practice both single cells and series and or parallel arrangements of these cells are called batteries the text of the article avoids the common misnomer in which a single cell is described as a battery . Series Connections A typical definition of series connections is an arrangement of cells in a battery made by connecting the positive terminal of each cell to the negative terminal of the next cell so that their voltages are additive. Such a definition covers the most common series arrangement in which the battery capacity is equal to the capacity of a single cell and the nominal battery voltage equals the nominal cell voltage multiplied by the number of cells. Implicit in
