Soaking of 4BS-cured pastes

The dependence of the amount of H2SO4 that has reacted with 10 g of 3BS or 4BS paste as a function of soaking time is shown in Fig. 3.10. 4BS pastes react with H2SO4 much more slowly than do 3BS pastes. The smaller surface area and the greater thickness of the crystals in 4BS pastes cause the rate of the reaction of sulfation to slow down within the first 30 min of soaking [11-16]. The structure of the lead sulfate layer that covers the 4BS crystals has been examined [11-14]. First, polyhedral particles with an average size of up to 2 pm are formed on the surface of 

Heat generation during the soaking step is proportional to the specific surface of the cured paste [14]. Thus, the temperature rise on soaking of 4BS pastes is half that for 3BS pastes. It is therefore not necessary to cool down the H2SO4 solution before filling into batteries with 4BS cured plates. 

It has been established that the rate of sulfation on soaking of 4BS pastes depends on the method of 4BS crystal formation. The various methods of 4BS production yield not only crystals of different size, but also different nature [17]. 

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