Lead Acid Battery Systems
Basic Chemistry of Lead Acid
Anode Reaction: 2H+(aq) + 2e− → H2(g)
Cathode Reaction: Pb(s) + 2H2O(l) → PbO2(s) + 2H+(aq) + 2e−
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)
Anode Reaction:PbSO4(s) + H+(aq) + 2e− → Pb(s) + HSO−4(aq)
Cathode Reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO−4(aq) + 3H+(aq) + 2e−
Nickel Cadmium Battery Systems
Basic Chemistry of Nickel Cadmium
Discharge: Anode Reaction: Cd + 20H – > Cd(0H)2 +2c –
Discharge Cathode Reaction: 2NiO(OH) + 2H2O +2e – > 2Ni(OH)2 + 2OH –
Net Discharge Reaction: 2NiO(OH) + Cd + 2H2O > 2Ni(OH)2 + Cd(OH)2
Note: During recharge the above reactions are reversed
Sizing the battery system for a specific location and application is based on a load profile identifying the applied loads vs. time as per the below example:
This information will identify several factors essential to size both the type and capacity of the appropriate battery system.
In general secondary batteries are manufactured in three categories
High Discharge Rate – Normally high applied loads for short periods of time.
Medium Discharge Rate – Normally variable loads within a moderate range of applied loads, possibly with short spikes for moderate periods of time.
Long Discharge Rate – Normally moderate applied loads for long periods of time.