Efficiency testing is a generic expression for electrical measurements of battery's state-of-health. This can be further broken down into impedance or conductance derived from an AC signal technique, or internal resistance derived from a DC technique.
The pitfalls in the diagnosis of a battery are the most varied due to a complex and non-linear electrochemical element and various factors that influence the reading, including the frequency, the amplitude of the test signal and the resolution of the test meter. This means that the readings acquired using a technique stimulus may not correspond to the readings acquired using another technique.
Throughout the life of the battery is essential consistency in both equipment and testing.
When data is acquired correctly and consistently, internal impedance has been shown to have a strong correlation with capacity and, although it is not a direct measure of capacity, it can be used as an index of State of Health to predict battery performance in a discharge. A 25% increase indicates a drop in performance from 100% to around 80%, so a 25-35% increase in internal impedance will be acceptable, with a standard replacement planning. Between the 35-50% increase in internal impedance we have a clearly physical signal on the degradation of the battery capacity which therefore is nearing the end of its life cycle. These last considerations are at the basis of the Life Test carried out by our CB and CBI true ADEL system's “Battery Care” philosophy.