The plates in a lead plate battery are of very large area per cell, and
are placed close together. Sometimes, as in Planté's battery, large flat
plates are laid together with a separating insulator between them, and
are then rolled into a spiral. Sometimes, the most usual arrangement,
the plates are in sets, the positive and negative ones alternating, and
each cell containing a number of plates.
To secure a good quantity of active material, the plates are sometimes
perforated, and the perforations are filled with oxide of lead. This
gives a good depth of material for the charging current to act on, and
avoids the necessity for a tedious "forming," q. v.
The electro-motive force of such a battery per cell is 2 volts. Its
resistance may only be one or two-hundredths of an ohm. An intense
current of many amperes can be supplied by it, but to avoid injuring the
cell a current far less than the maximum is taken from it.
To charge it, a slightly greater electro-motive force, the excess being
termed spurious voltage, is required.
Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY.