BASIC ELECTRONICS - OD1633 - LESSON 1/TASK 2
The low-voltage limit, as specified by the manufacturer, is the limit beyond
which very little useful energy can be obtained from a battery. This low-
voltage limit is normally a test used in battery shops to determine the
condition of a battery.
b. Combining Cells.
In many cases, a battery-powered device may
require more electrical energy than one cell can provide.
The device may
require either a higher voltage or more current, and in some cases both.
Under such conditions, it is necessary to combine or interconnect a
sufficient number of cells to meet the higher requirements. Cells connected
in series provide a higher voltage, while cells connected in parallel
provide a higher current capacity.
To provide adequate power when both
voltage and current requirements are greater than the capacity of one cell,
a combination series-parallel network of cells must be used.
(1) Series-Connected Cells. Assume that a load requires power supply
of 6 volts and a current capacity of 1/8 ampere.
Since a single cell
normally supplies a voltage of only 1.5 volts, more than one cell is needed.
To obtain a higher voltage, the cells are connected in series as shown in
figure 60 on the following page.
View B in figure 60 is schematic representation of the circuit shown in view
A. The load is shown by the resistance symbol and the battery is indicated
by one long and one short line per cell.
In a series hookup, the negative electrode (cathode) of the first cell is
connected to the positive electrode (anode) of the second cell, the negative
electrode of the positive of the third, etc. The positive electrode of the
first cell and the negative electrode of the last cell then serve as the
terminals of the battery. In this way, the voltage is 1.5 volts for each
cell in the series line.
There are four cells, so the output terminal
voltage is 1.5 x 4, or 6 volts.
When connected to the load, 1/8 ampere
flows through the load and each cell of the battery.
This is within the
capacity of each cell.
Therefore, only four series-connected cells are
needed to supply this particular load.