Page 383 - Battery Reference Book

32/10 Lead-acid secondary batteries
11OP

100 -

-
90
- -
r
a
s 80
.-
c
P
8 70-
-
Q -
.-
J 60 -
a
50 -
40-
I I I I I I I I I
0 20 40 60 80 100 120 140 160 180 200
Discharge current (A)
Figure 32.5 Capacity on intermittent discharge at 30°C. (Nominal cell capacity lOOAh in 5 h) (Courtesy of Chloride Batteries)

To cover these factors, it is accepted that a battery 32.3 Starting, lighting and ignition (SLI)
should not be regularly discharged by more than about or automotive batteries
80% of its normal capacity. This is also good battery
operating practice to protect it against overdischarge These are discussed in Part 6.
and general abuse.
Therefore, the ampere hour value should now be
divided by a further factor of 0.80. 32.4 Partially recombining sealed
Figure 32.6 shows how a battery’s life and therefore lead-acid batteries
the cost per kilowatt hour of output is affected by the
depth to which the battery is discharged each day; thus These batteries may be used in either cyclic or float
the necessity for the above calculation. service in a wide range of applications which include:
To summarize so far, we have reached a calcula- point of sales terminals of centrally controlled cash
tion of register systems, electronic cash registers, portable test
Nominal 5-h capacity required
I I 120 r
= ampere hours consumed by the motor x - -
x
0.70 0.80
I 110
= ampere hours consumed by the motor x ~
0.56 L:
This final figure represents the total nominal battery 2 loo
capacity required for the duty of the vehicle. zi
It will now be apparent whether one, two or three n
batteries will be needed, and, at this stage, it is import- g 90
ant to lay down a suitable working schedule, which u
will ensure that the work of each battery is shared
equally between recharges. 80
On no account should a battery be worked until the
vehicle’s performance begins to deteriorate. It is far
better either to ensure that the duty does not make this 60 70 80 90 100 110
demand, or to change the battery before recharging.
In terms of efficient performance, and increased bat- Daily discharge (% of nominal capacity)
tery life, it is far more economic to organize battery
charging routines that avoid this situation. Figure 32.6 Battery cost for different extents of daily discharge
(Courtesy of Chloride Batteries)