An emergency power plant can be assessed and inspected regardless of how it can be used where numerous measures are involved. Visual inspection of the battery cases and poles are included with connections and connectors, measuring temperature. Charging devices can be controller and testing of the capacity so that weak and defective batteries can be detected.
The battery condition can be determined reliably with a complex capacity test which is carried out often. The complete discharge of the battery can be determined by the actual and current capacity (AGM or gel batteries and batteries which are also with liquid electrolytes).
In many cases, it is not possible any longer for cost reasons and can be carried out only in a reduced form by users most. The discharge test reliability is reduced considerably.
The significance of measuring voltage is little. “Voltage experts” has been developed by many service technicians. The battery voltage can be measured as they make a statement for individual problems of the battery.
The voltage measurement at best gives information that is reliable for the state of charge but is not about the batteries remaining capacity. No information is provided by measuring the voltage about the life expectancy that is expected. A bad battery is charged with the same open-circuit voltage of approx. 2.09V which is a good battery to charge.
The information about the current capacity is obtained with a discharge test with corresponding current consumption that can be carried out with a voltage limit of 1.8V/cell that can be reached.
Source:- Elektrotechnik.vogel