Page:Popular Science Monthly Volume 88.djvu/809

 Popular Science MontJily

��781

��Lamp Resistance for Charging Storage Batteries

A LAMP bank resistance for reduc- ing current in charging storage batteries, while wasteful of energy, is cheap in construction and is often use- ful in power houses or in those few places were electric current is abnor- mally cheap. The lamps are inserted in holes bored in a soft pine plank, mak- ing contact on the lower side with strips of copper or brass that are fastened by tacks. Contact with the other lamp ter- minals — the threaded bushings — is made by winding clean copper wire in a zig- zag fashion between the lamps' bases, as indicated in the diagram. The wire should be wound about each lamp base several times to secure adequate contact, and soldered, if possible. A fuse block should be provided and the connections made as shown.

Old lamps are best, as their resistance is lower than new ones. If the polarity of the current is not known it can be found by placing one wire of the circuit in a tumblerful of water with a wire from the lamp bank opposite. Only a couple of lamps should be used in this test. By noting the bubbles that arise from the two wires, the polarity can be determined by marking the wire from which most bubbles rise. This is the negative side. Storage batteries will be ruined if the connections are not correct- ly made.

��So/f wafer ^^

��Bore /7o/ej/n do//er(/ \

����Method of recharging dry batteries by immersing them in salt water

��A simply arranged lamp bank for reducing voltage when charging storage batteries

Recharging Worn-out Dry Batteries

DRY batteries are made of dampened carbon cobalt. That all batteries have not the same life is due to the fact that they are dry from use, or leakage from evaporation through the top. Cheap batteries do not contain the quality of carbon found in high-grade batteries ; hence it is useless to recharge cheap ones. A good high-grade battery will recharge three times before it is worthless.

Take six worn out batteries, drill four holes in the top of each through the tar covering (a red hot nail or a small drill will do), so that the black carbon can be seen. Fill a pail with water, so that it will be about one inch higher than the tops of the batteries. Dissolve three good handfuls of common table salt in the water. Do not use sal-ammoniac. Place the batteries in the pail in a stand- ing position. Leave them for eight hours, stirring the salt water about twice during that time.

After removing the batteries, stand them upside down to let what water will run out (about two hours). Then seal them with a hot soldering iron ; connect them, and they are ready for use. This can be done three times. — T. F. BusCH.

�� �