A sensor of sulfuric acid specific gravity for lead-acid batteries

On the basis of the dependence of the electrode potential on the sulfuric acid concentration, three electrodes used as the sensors have been investigated. Since, it is hard for the potential of the PbSO4/PbO2 electrode to be stable in sulfuric acid solution, this electrode is not suitable to be a sensor. For the Pb/PbSO4 electrode used as a sensor, the stability of its potential depends on its porous structure. The higher the porosity of the negative electrode is, the shorter the response time. The potential of the Pb/PbSO4 electrode is proportional to the logarithm of the sulfuric acid specific gravity. Compared with other sensors, this sensor developed in present work has a shorter response time, and hence, the measurement is more accurate. In the estimation of the residual capacity in a real lead-acid battery, its error is about 4%. The disadvantage of this sensor is that it still needs renewing periodically by a short charge.