Whether it’s for single point back-up capability or for a larger scale UPS attached to a POE switch or mid-span injector, the back-up battery is the unseen component that is expected to operate when the unexpected happens . Too often, this component is ignored, and, most often, little thought or action is given to maximizing its lifetime and efficiency. 

The Basics

First, let’s provide a little background on batteries . Most batteries used in the security and fire alarm industry are of the lead-acid type, the same basic technology used in most conventional automobiles . Despite their larger size versus other types of batteries, the cost per watt still makes them suitable in many applications where size is not a large detriment . Invented in 1859, lead acid batteries are the oldest type of rechargeable battery .

The battery has several main components: electrodes, plates, electrolyte, separators, terminals, and housing . The positive and negative electrodes are rigid metallic grids; usually perforated or grooved to maximize surface area; constructed of lead dioxide and lead, respectively; and employing separators between them to avoid short circuiting.

The electrolyte is a sulfuric acid, containing aqueous H+ and SO4-2 ions . A cell will produce 2 .1 - 2 .3 volts and is usually connected in series with other cells to produce higher voltages, typically 12 or 24 VDC . Terminals are fastened to the end positive and negative electrodes and protrude through the plastic case housing. 

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