Details of Lead
We use a lead acid battery in our project as it is readily available. Lead Acid battery consists of lead
as terminal and sulphuric acid as electrolyte.
Cathode is oxidized
Initial charging establishes which plate will be the anode, and which the cathode. The process is driven by the forcible removal of electrons from the cathode and the forcible introduction of them
to the cathode. This splits the water into Hydrogen (which bubbles and is drawn off) and Oxygen,
which binds with the lead on the cathode, producing lead (II) oxide.
Anode Reaction: 2H+(aq) + 2e− → H2(g)
Cathode Reaction: Pb(s) + 2H2O(l) → PbO2(s) + 2H+(aq) + 2e−
During discharge, both plates are again
returned to equal composition, but this time both plates become lead sulfate.
The process is driven by the conduction of electrons from the cathode back into
the cell at the anode.
Anode Reaction: Pb(s) + HSO−
4(aq) → PbSO4(s) + H+(aq) + 2e−
Cathode Reaction: PbO2(s) + HSO−
4(aq) + 3H+(aq) + 2e− → PbSO4(s) + 2H2O(l)
Subsequent charging places the battery back in
its charged state, changing the lead sulfates
into lead and lead oxides. The process is driven by the forcible removal of electrons from the anode and the forcible introduction of them to the cathode.
Anode Reaction: PbSO4(s) + H+(aq) + 2e− → Pb(s) + HSO−
Cathode Reaction: PbSO4(s) + 2H2O(l) → PbO2(s)
4(aq) + 3H+(aq) + 2e−
Figure 2.3: The state of charge in a battery can be determined by measuring its open circuit voltage.
Acid Battery Charger details and working
Although a lead acid battery can technically be charged just by providing a higher potential difference from the solar cell across it, it is important to monitor the level of charge across it and disconnect when the battery reaches full charge.
It is important to regulate charging to avoid overcharging.
A single event of overcharging can reduce battery capacity by 10-15%