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FIAMM Energy Technology S.p.A
Installation & Operating Instruction -Technical Manual
Edition 03/2018 Rev.7
2.
OPERATING FEATURES
2.1.
Capacity
The battery capacity is rated in ampere hours (Ah) and
is the quantity of electricity which it can supply during
discharge. The capacity depends on quantity of active
materials contained in the battery (thus on dimensions
and weight) as well as the discharge rate, and
temperature, and minimum voltage.
The nominal capacity of FET batteries refers to the 10
(or 20) hrs discharge rate (indicated with C
10
or C
20
)
with constant current at 20°C to 1.80 (or 1.75 per C
20
)
volt per cell.
Fig. 1: Typical discharge curves for FET AGM batteries (FIT range)
2.2.
Capacity in relation to discharge rate
The available capacity of all lead acid batteries depends
on discharge rate (discharge current); this is due to
internal
electrochemical
process
and
type
of
construction (i.e. type of positive plate).
Fig. 2: Average available capacity versus discharge rates for FET AGM
batteries
2.3.
Capacity range of FET AGM Lead Acid
Batteries
FET Battery
range
Battery Capacity
[Ah]
FG
from 1.2 to 70
FGC
from 12 to 42
FGH
from 5 to 18
FGHL
from 5 to 12
FGL
from 17 to 205
FIT
from 40 to 195
FHT
from 95 to 180
SLA
from 25 to 2000
FLB
from 26 to 235
2.4.
Capacity in relation to the temperature
The capacity available from a battery, at any
particular discharge rate, varies with temperature.
Batteries which have to operate at temperatures
different from the nominal (20°C) need a higher or
lower capacity as per the factor indicated in the
following graph (required capacity has to be divided
by the correction factor stated in the graph).
Fig. 3: Capacity Correction factor versus temperature for a 10 hours
discharge rate for FET Lead Acid AGM batteries
2.5.
Internal impedance and short circuit
current
The internal impedance of a lead acid battery is a
direct result of the type of internal construction, plate
thickness, number of plates, separator material,
electrolyte sp. gr., temperature and state of charge.
The internal resistance and the short circuit current of
FET VRLA batteries at 100% state of charge and
20°C
is indicated in the relative Product Sheet. These
values are calculated in accordance with IEC 60896
part 21/22.
Different instruments are available to detect the
internal resistance or impedance of lead acid
batteries. These instruments use a different way to
determinate these values. The values obtained from
9
9.5
10
10.5
11
11.5
12
12.5
13
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
B
lo
c
V
o
lt
a
g
e
(
V
o
lt
)
hours
I=0,85 C10
I=
0,15 C10
I=
0,1 C10
I=
0,27 C10
I=0,5 C10
I=
0,088 C10
0
20
40
60
80
100
120
0
2
4
6
8
10
av
ai
la
bl
e
c
apa
ci
ty
[
%
]
hours
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Te
m
pe
ra
tur
e
c
or
re
ct
ion
f
ac
tor
Temperature
15 -30 min. discharge rate
1-10 hours discharge rate
-20°C
-10°C
0°C
10°C
20°C
30°C
40°C
50°C