How to assess the health of a battery: the efficiency test

The efficiency test is a generic expression for the electrical measurement of the health of a battery. This can be divided into impedance or conductance derived from an AC signal technique or internal resistance derived from a DC technique.

The Challenges in Battery Diagnosis.

The pitfalls in diagnosing a battery are most varied because of a complex, nonlinear electrochemical element and various factors affecting the reading, including frequency,amplitude of the test signal, and resolution of the test meter. This means that readings acquired using one stimulus technique may not match readings acquired using another technique.

Throughout the battery life, it is essential to maintain consistency in both equipment and test procedure.

Consistency and Correlation with Capacity.

It has been shown, when data are acquired correctly and consistently, thatinternal impedance has a strong correlation with capacity and, although not a direct measure of capacity, can be used as an index of health to predictbattery performance in discharge. A 25% increase indicates a drop in performance from 100% to about 80%, so a 25-35% increase in internal resistance will be acceptable with a standard replacement schedule. Between 35-50% increase in internal resistance we have a clear physical signal about the degradation of battery capacity, which is therefore approaching the end of its life cycle. These latter considerations are the basis of the Life Test carried out by our CB and CBI, true flagships of ADEL system's "Battery Care" philosophy.