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FIAMM Energy Technology S.p.A
Installation & Operating Instruction -Technical Manual
Edition 03/2018 Rev.7
3.
CHARGING
In order to ensure the best protection against power
failures in any moment, it is necessary that batteries are
kept in the following conditions:
in float charging throughout all their standby period;
fully recharged soon after a discharge,
completely recharged after a discharge. Recharge as
soon as possible to ensure maximum protection
against subsequent power outages. Early recharge
also ensures the maximum battery life.
3.1.
Floating charge
Floating battery systems are those where the charger, the
battery and the load are connected in parallel.
The "float" setting will maintain the battery in a fully
charged state with minimal water consumption.
The voltage recommended for float charge is 2.27 V at
20°C. The recommended float voltages to maximize the
battery life over the range of temperatures between -20
and +60°C are shown in the figure 6 or using the
formula:
-2.5mV/cell/°C
The normal float current observed in fully charged FET
front terminal batteries at 2.27 VPC and a temperature of
20°C is approximately 0.3 mA/Ah. Because of the nature
of recombination phenomena, the float current observed
in the case of the FET front terminal batteries is normally
higher than that of vented batteries and is not an
indication of the state of charge of batteries.
Fig. 6 : Recommended Float Voltage at different temperatures
3.2.
Boost charge (Recharge following a
discharge)
Boost charge has to be used to recharge a battery after a
discharge; it will restore the battery to a fully charged
state within a relatively short period of time. Use a
constant voltage 2.40 V/cell at 20°C with a
maximum
current of 0.25 C
10
. However this recharge should be
limited to no more than once per month to ensure the
maximum service life of the battery. Temperature has to
remain lower than 35°C.
Fig. 7 : Recharge curves at 2.40 V/cell with different limit of current
-4
14
32
50
68
86
104
122
140
-20
-10
0
10
20
30
40
50
60
2.19
2.21
2.23
2.25
2.27
2.29
2.31
2.33
2.35
Te
m
p
e
art
u
re
[°
F]
T
e
m
p
e
ra
tu
re
[°
C]
Float Voltage [V/cell]
0%
20%
40%
60%
80%
100%
120%
0
5
10
15
20
R
e
ch
a
rg
e
d
C
a
p
a
ci
ty
[A
h
]
Time [hours]
I=0.15 C
10
I=0.10 C
10
I=0.05 C
10