Page 187 - Uninterruptible Power Supplies

Source: Uninterruptible Power Supplies and Standby Power Systems

Chapter
7

Batteries

Introduction

It is said “95 percent of UPS problems are induced by battery/human
error problems,” a sweeping statement, nevertheless one in general
vogue at the moment. True, in the early days of development of the pop-
ular sealed lead acid battery, now correctly identified as the valve reg-
ulated lead acid (VRLA) battery, reliability was not high. Since that
time some 20 years ago, there have been constant developments in
design resulting in a reliable performance. This chapter therefore goes
into some detail on types of VRLA cells available and also covers the
flooded-type cells available today.

Types of Cell
Among the variety of secondary (rechargeable) cells available, only
two are in use for UPS applications. These are lead acid and nickel-
cadmium batteries. Both of these are available in differing types, each
type having its own characteristics and qualities affecting choice and
application.

Lead Acid

Lead acid cells having a chemical process which in simplistic terms
consists of electrodes constructed from lead and lead dioxide in a dilute
sulphuric acid solution. If the potential is measured between the two
electrodes, an approximate reading of 2 V is apparent.

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