User manual

Table 6-1 (1.5C10 inrush)
Charge time at 2.45VPC Capacity Returned
17 min. 50%
27 min. 80%
31 min. 90%
60 min. 100%
Table 6-2 (2.5C
10 inrush)
Charge time at 2.45VPC Capacity Returned
12 min. 50%
19 min. 80%
24 min. 90%
40 min. 100%
These tables demonstrate the superior fast charge capabilities
of the CYCLON
®
line of sealed-lead batteries. The numbers in
Table 6-1 were generated using an initial current in the 1.5C
10
range while those in Table 6-2 were generated using a current
limit in the 2.5C
10 range.
Increasing the magnitude of the inrush current has a dramatic
impact on the total time to recharge the cells -only 40 minutes
to return 100% of previously discharged capacity at 2.5C
10
compared with 60 minutes at 1.5C
10 to reach the same mark.
This is a useful result to keep in mind when designing battery
systems for applications that require rapid opportunistic
charging.
Although CYCLON battery cells do not require a current limit
(initial current inrush) when being charged by a CV source,
most practical applications have chargers that have limited
power handling capabilities, thereby also restricting the
current limit.
Cyclic charging tests were conducted using a CV charger
that had only a 1A (C
10/2.5 on a 2.5Ah cell) current limit and
the charge times shown in Table 6-3. The charge voltage,
however, was set at 2.45 VPC. The last column shows the
number of cycles one may expect for specific DOD numbers.
Table 6-3
Depth of Charge
3
time, hr. Number of cycles
discharge, %
2
Up to 30 5 2500
31 to 50 8 1700
51 to 100 16 300
6.6 Float Charging
When CYCLON battery products are in a purely float
application at an ambient temperature of 25°C (77°F), the
recommended charge voltage setting is 2.25 to 2.30 volts per
cell (VPC). We also recommend that this charge voltage be
temperature compensated, as outlined in the next section.
6.7 Temperature Compensation
High temperatures accelerate the rate of the reactions that
reduce the life of a cell. At increased temperatures, the
voltage necessary for returning full capacity to a cell in a
given time is reduced because of the increased reaction rates
within the battery.
To maximise life, a negative charging temperature coefficient
of approximately ±3mV per cell per °C variation from 25°C
(77°F) is used at temperatures significantly different from
25°C (77°F). This coefficient is negative - as the ambient
temperature increases the charge voltage must be reduced,
and vice versa. Figure 6-1 shows the variation of float voltage
with temperature.
It is important to note that even if the charge voltage is
perfectly compensated for high ambient temperature, the
float life expectancy of the cell would still be reduced.
This is due to the fact that while the charge currents are
lowered because of lower charge voltages, the high ambient
temperature continues to have a negative influence on the life
of the battery. Thus, temperature compensation of the charge
voltage only partially offsets the impact of high ambient
temperature on the float life of the cell.
Figure 6-1: Variation of Charge Voltage with Temperature
2
Discharged at C10/5 (460mA) to 1.70 VPC
3
Constant voltage charge at 2.45 VPC with inrush current limited to 1A (C10/2.5 for a 2.5Ah cell)
Applied battery charging voltage vs temperature
2.45 VPC@ 25ºC for cyclic (fast) charge
2.27 VPC@ 25ºC for float (slow) charge
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.80
2.90
-40-35-30-25-20-15-10-5 0 5 101520253035404550556065707580
Temperature, ºC
Applied battery charge voltage (VPC)
Theoretical cycling (ideal)
V=0.00004T
2
- 0.006T + 2.5745
Theoretical float (ideal)
V=0.00004T
2
- 0.006T + 2.3945
and 2.20VPC minimum
13
Publication No: EN-CYC-AM-007 - December 2008
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