Introduction to Formation Shop
The basic materials in battery production are lead alloys to make the grids and lead oxide for the active material. The grids are used as a support for the active material and as electric conductors for the current.
Lead oxide is produced in Ball mills operating on a surface oxidation of lead. The oxide particles always contain some residual metallic lead which is separated and carried away by an air stream then collected in filters.
The plates for all automotive batteries and most industrial batteries are made by preparing a paste from lead oxide with fairly strong sulfuric acid then pressing this paste into the grids. After surface drying, the plates are cured in moisture saturated air at slightly elevated temperature and then dried.
The paste preparation and curing are very important steps and any mistakes or faults therein cannot be fully repaired later. Most problems arising in formation are due to compromises in these steps.
The initial formation charge of a lead-acid battery is quite a complex bundle of chemical reactions. It is important to know in principle about the most important parameters controlling this process in order to achieve good reproducible results with reasonable efforts.
To begin, formation positive and negative plates are inserted into diluted sulfuric acid and connected to a bus bar. The rectifier acts like a pump removing electrons from the positive plates and pushing them into the negative ones. The following reaction equations are simplified showing the essentials.
Positive: PbSO4 + 2H2O --> PbO2 + H2SO4 + 2e- + 2 H+
Negative: PbSO4 + 2e-+2H+ --> Pb + H2SO4
Lead oxide is produced in Ball mills operating on a surface oxidation of lead. The oxide particles always contain some residual metallic lead which is separated and carried away by an air stream then collected in filters.
The plates for all automotive batteries and most industrial batteries are made by preparing a paste from lead oxide with fairly strong sulfuric acid then pressing this paste into the grids. After surface drying, the plates are cured in moisture saturated air at slightly elevated temperature and then dried.
The paste preparation and curing are very important steps and any mistakes or faults therein cannot be fully repaired later. Most problems arising in formation are due to compromises in these steps.
The initial formation charge of a lead-acid battery is quite a complex bundle of chemical reactions. It is important to know in principle about the most important parameters controlling this process in order to achieve good reproducible results with reasonable efforts.
To begin, formation positive and negative plates are inserted into diluted sulfuric acid and connected to a bus bar. The rectifier acts like a pump removing electrons from the positive plates and pushing them into the negative ones. The following reaction equations are simplified showing the essentials.
Positive: PbSO4 + 2H2O --> PbO2 + H2SO4 + 2e- + 2 H+
Negative: PbSO4 + 2e-+2H+ --> Pb + H2SO4