Always be sure to use large wire in connecting cells. Fine wire offers considerable resistance to the electrical current and the full benefit of the batteries cannot be secured when it is used.
[Illustration: FIG. 35.—Showing how to connect a Battery of Cells in
Series-Multiple.]
Use care to scrape all connections so that they are clean and bright. Tighten the binding posts with a pair of pliers so that there is no chance of their becoming loose.
Another wise precaution is to always arrange batteries so that there is a small space between two cells and no likelihood of any of the wires or binding posts coming into contact with one another so as to form a short circuit.
After the connections have been carefully made a little vaseline smeared over them will prevent corrosion.
[Illustration: FIG. 36.—Battery Connectors like that shown above can be obtained for 1 1/2 cents each and will be found to be very handy.]
Storage or Secondary Cells.
Storage or secondary cells (also sometimes called accumulators), differs from primary cells in that they will not give forth an electric current until they have been *charged* by passing an electric current through them.
[Illustration: FIG. 37.—A Simple Experimental Storage Battery consisting of two Lead Plates immersed in Dilute Sulphuric Acid.]
The Storage Cell is therefore a very convenient means of taking electric energy at one time or place and storing it up for future use. From this it must not be implied that electricity is actually stored in such a battery. The energy of the electric current is really changed into chemical energy and this energy produces electricity when the cell is again discharged.