Page 377 - Battery Reference Book

32l4 Lead-acid secondary batteries
sulphuric acid is pressed. The negative plate is also
of the pasted grid type, but is thinner.
Although this is the basis of the modem car battery,
car batteries are wholly unsuitable as an emergency
power source because they are designed to give high
current for a short time, as when starting a car engine.
Like the Plant6 battery, pasted plate batteries man-
ufactured for standby use have transparent containers.
They are available in capacities of up to 500Ah and
have a life expectancy of 10-12 years to meet emer-
gency lighting regulations.

Tubular cells
Cells with tubular positive plates are normally used
to power electric trucks, on which daily recharging
is needed. They are also suitable for certain standby
applications. They deliver high power at low and
medium rates of discharge and work well in adverse
conditions.
The positive plate consists of lead alloy spines sur-
rounded by synthetic fibre tubes filled with a mixture
of lead oxides (Figure 32.3). The tubes keep the active
material in contact with the conducting spines during
expansion and contraction resulting from the charge
and discharge cycle, and so contain the stresses that
would break up other types of plate.
Tubular cells are ideal for any kind of applica-
tion that requires frequent charge/discharge cycles.
When on standby duty, they have a life expectancy
of 10-12 years, compared to 5 years when powering
an electric truck. They are less costly than Plant6 cells,
but fall in capacity as time goes on.
Table 32.1 shows the types of application for each
of these types of battery as recommended by a lead-
ing manufacturer of standby power batteries, Chloride
Storage Batteries Ltd, UK.

Figure 32.2 Layout of a typical modern flat Plante-type lead-acid Figure 32.3 Layout of a modern design of lead-acid tubular cell
standby battery (Courtesy of Chloride Batteries) standby battery (Courtesy of Chloride Batteries)