AC ripple effects on VRLA batteries in float applications

The gaps observed between life predictions developed by VRLA battery manufacturers and those obtained by users in UPS and telecom field applications has been ascribed to abusive installation conditions, large temperature variations and/or an inherent deficiency in the technology that prevents proper float charging. This paper suggests that the power quality used to float charge VRLA batteries may be an additional factor contributing to shortened field lifetimes. It is shown from past literature that the presence of so-called "AC ripple", in its purest form, can have both useful and destructive effects on battery performance. However, it is suggested that a variant of this phenomenon, referred to as "high-frequency shallow cycling", may have a key role in a number of float applications where VRLA batteries fail prematurely.