Old batteries can be tested with an appropriate procedure which is possible by evaluating an old battery system by means of conductivity measurement. With the last capacity test to be in connection so that the original start conductance can be determined where the limit conductance can be derived with an indication of the battery needs to be replaced.
It is interesting, particularly that the same quality batteries with residual capacity can be put together without the disposal of all batteries in one shot. Conductivity measurement accordingly is used as quality control for new batteries.
Source:- Elektrotechnik.vogel