1. Batteries
A galvanic cell or a group of galvanic cells connected in series
Source of portable power
Several types of battery in use today; we’ll look at two

2. Electrochemistry
Batteries

3. Lead Storage Battery Pb + HSO4-  PbSO4 + H+ + 2e-
PbO2 + HSO4- + 3H+ + 2e-  PbSO4 + 2H2O
Car battery has six of these connected in series.
Each cell produces ~ 2 V so the battery has a 12 V potential.

4. Lead Storage Battery
In a car the battery is continuously recharged by the alternator.
If allowed to run down, PbSO4(s) builds up on the surface of the grids.
Applying a current reverses the reaction and removes the PbSO4.

5. Dry Cell Battery Acid version: Zn  Zn2+ + 2e-
2NH4+ +2MnO2 +2e- Mn2O3 +2NH3 +H2O
Alkaline version:
Zn + 2OH-  ZnO + H2O + 2e-
2MnO2 + H2O + 2e-  Mn2O3 + 2OH-

6. Dry Cell Battery
Alkaline version lasts longer since Zn corrodes less rapidly under basic conditions
All cells from AAA to D provide ~1.5 V.
Larger cells provide more current.

7. Other Types of Batteries
Mercury batteries can be very small
Lithium-iodide batteries are lightweight and long-lasting.
Also Ni-Cd and Ni metal hydride types

8. Batteries
Fuel Cells

9. Fuel Cells
Galvanic cell for which the reactants are continuously supplied.
Primary reaction under study is:
2H2(g) + O2(g)  2H2O(l)
Fuels cells of this type used by NASA, but not practical for general use yet.