Abstract: A method for determining the state of charge (SOC) of a battery by measuring its open circuit voltage (OCV) either with the battery in a fully rested state of chemical and electrical equilibrium or an active state during a period in which the battery settles after charge or discharge is stopped. A first type algorithm is developed to correlate the OCV in a fully rested condition (OCVREST) to the state of charge at which that measurement is taken. A second type algorithm is developed that predicts a final settling OCV of a battery (OCVPRED), based on the set of parameters of OCV, rate of change of OCV, and battery case temperature, acquired during the settling period of a battery not at rest. To determine the SOC of a battery being tested that is in the fully settled state the measured OCVREST is applied to the first type algorithm.

Abstract: Deficiencies in the electrolyte level of the cells of NiCd battery can be detected by measuring the internal resistance of the cells. Initially, data is collected for a battery type and capacity, correlating measured internal resistance with the amount of water that must be added to bring the cell resistance to an acceptable value. Subsequently, cells of other batteries of the same type and capacity can be measured to determine how much water must be added and the levels quickly restored. The polarization value of the cells can be used lieu of the internal resistance in the same fashion.

Abstract: A method and apparatus for diagnosing the status of a battery having high and low voltage plateau states corresponding to its state of charge in which the battery open circuit voltage is measured (S106) to determine its voltage state and its internal resistance also is measured (S114). A battery having a low voltage state (S116) is tested to determine if its internal resistance is greater than a predetermined maximum resistance (S118) and if it does the battery is considered as possibly having a low electrolyte level, and if it does not the battery is subjected to a current ramp test to determine from the voltage response a point of current transition (S130) due to a battery chemical gassing reaction. The battery state of charge (S132) is determined from curves or algorithms of state of charge versus current transition.

Abstract: A system and method for comprehensive analysis of a multi-cell battery, such as of the nickel-cadmium type, on an individual cell level basis and overall battery basis. For an unsealed battery, which affords access to the individual battery cells, (FIG. 2) tests are carried out to determine the presence of any shorted or reversed cells, and these can be repaired or replaced ((6)-(11)). The individual cells are then tested for sufficient electrolyte on the basis of comparing the cell internal resistance to a maximum internal resistance for the cell and electrolyte added as needed ((12)-(15)). A sealed battery, to which there is no access to the individual cells, is first tested for shorted or reversed cells on a battery level basis ((16)-(19)).