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APPLICATION GUIDE
RESERVE
POWER
Introduction
EnerSys® has optimised the very successful Thin Plate Pure Lead
(TPPL) PowerSafe® SBS® battery range to create the revolutionary
EON Technology®, a concept that utilises highest purity materials and
state of the art manufacturing processes to deliver energy storage
solutions that can meet the requirements of emerging applications
whilst offering the end user enhanced performance in existing
applications. Historically, the useful service life of reserve power
Valve Regulated Lead Acid (VRLA) battery systems was measured by
their float life but as applications evolve from pure standby to cyclic
applications, some traditional VRLA technologies find that these new
requirements push them beyond their scope of operation.
PowerSafe SBS EON Technology monoblocs and cells retain the long
float characteristics of standard PowerSafe SBS monoblocs and cells,
with the added benefit of improved cyclic ability in both float voltage
and fast charge applications.
Table 3 provides a summary of the operating parameters (charging)
that will deliver optimum service life and performance relative to the
type of application.
Application
PowerSafe® SBS® EON Technology®
Charge Parameter for Optimised Life and
Performance
Float charge
(reliable AC power)
Temperature compensated float voltage
equivalent to 2.29Vpc @ 20°C
Charge current - minimum 0.1C10A,
maximum unlimited
Float charge
unreliable
AC power
(uncontrolled PSOC)
Boost voltage equivalent to 2.40vpc
@ 20°C to fast charge
Charge current - minimum 0.1C10A,
maximum unlimited
Followed by float voltage with temperature
compensation applied as required
Hybrid operation to
full state of charge
Boost voltage equivalent to 2.40Vpc
@ 20°C
Charge current - minimum 0.1C10A,
maximum unlimited
Return to full state of charge between
discharge cycles
Optimum charge factor 103% of
discharged Ah
Hybrid operation
in partial state of
charge
(controlled PSOC) example
Boost voltage equivalent to 2.40Vpc
@ 20°C to return to 95% state of charge.
Charge current - minimum 0.1C10A
Full recharge every 10 days
EnerSys will consider variations in
controlled psoc operation as necessary please contact your local representative to
discuss details
Applications
PowerSafe SBS EON Technology solutions are well proven in stand
by applications, recent developments have focused on improving
robustness in harsh environments and challenging operating
conditions, so that today EON Technology has higher cyclic
performance, improved endurance at high temperature and the
ability to operate in partial state of charge conditions, providing that
the operating conditions are well understood.
Float charge mode:
Stable reliable grid, stable ambient temperature, compensation
to float voltage for any temperature fluctuation and no or very
little cyclic use (<10 cycles per year).
Grid assist applications:
Quite a stable grid and ambient temperature, medium level of
cyclic use (50 to 100 cycles per year) with low risk for partial state
of charge cycling.
Partial state of charge:
Unstable grid, warm ambient temperatures with uncontrolled
cyclic use meaning high risk for partial recharge.
Off grid applications:
Typically diesel generator and battery hybrid, it can also
incorporate renewable energy sources such as wind turbine or PV
array to alternatively supply energy to telecoms equipment,
where mains grid power is not available. Warm ambient
temperature with regular cyclic duty – typically 1 cycle per day.
Table 1
Off grid applications can be further split into two sub categories as
shown in table 2.
Controlled partial state of charge:
An operating mode with regular cyclic duty where the battery is
deliberately operated in partial state of charge to maximise
operating expenditure savings. The battery is periodically returned
to full state of charge when predefined trigger points are reached.
Can be subjected to high ambient temperatures.
Table 2
2
Operating Temperature Range
The recommended operating temperature range for optimum life and
performance is 20°C. However, PowerSafe SBS EON Technology
monoblocs and cells can be operated in the temperature range -40°C
to +50°C.
In order to maintain mechanical integrity of the plastic components,
the battery temperature in operation should not exceed +50°C.
Storage
Monoblocs and cells lose capacity when standing on open-circuit
because of parasitic chemical reactions. The self-discharge rate of
PowerSafe SBS EON Technology monoblocs and cells is very low
because of the high purity of the grid lead and electrolyte. Monoblocs
and cells should be stored in a cool, dry area. High temperature
increases the rate of self-discharge and reduces storage life.
Figure 1 shows the relationship between open-circuit voltage (OCV)
and storage time at various temperatures.
2.17
100
2.16
96
2.15
91
2.14
87
2.13
83
2.12
79
2.11
+40°C
2.10
Figure 1
0
+30°C
6
+25°C
12
18
+20°C
24
30
Months
74
+10°C
36
70
42
48
Approx. State of Charge (%)
Controlled full state of charge:
An operating mode with regular cyclic duty where the battery is
returned to full state of charge between discharge cycles. The duty
cycle is designed to optimized balanced battery life and operating
expenditure savings. Can be subjected to high ambient
temperatures.
Table 3
Open Circuit Voltage per Cell
Table 1 below gives description of the range of reserve power
applications covering stable grid, unreliable grid and off grid
applications – the superior performance characteristics of PowerSafe
SBS EON Technology makes it the ideal solution to be used in these
applications.
The maximum storage times before a freshening charge is required
and recommended open circuit voltage audit intervals are:
Temperature
(°C / °F)
Storage Time
(Months)
OCV Audit Interval
(Months)
+10 / +50
+15 / +59
+20 / +68
+25 / +77
+30 / +86
+35 / +95
+40 / +104
48
34
24
17
12
8.5
6
6
6
4
4
3
2
2
Commissioning Charge
Float Volts Per Cell
Freshening Charge
Charge the monoblocs or cells at a constant voltage equivalent to 2.29
to 2.4Vpc with 0.1C10 Amps current for a period of 24 hours.
2.35
2.34
2.33
2.32
2.31
2.30
2.29
2.28
2.27
2.26
2.25
2.24
2.23
2.22
2.21
2.20
2.19
Recommended Float Voltage
Minimum Float Voltage
Voltages >Recommended promote
overcharge & high float currents resulting
in accelerated end of service life
Voltages <Minimum recommended
result in undercharge, reduction in
capacity and irrecoverable capacity
loss leading to premature end of life
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Temperature (°C)
Figure 4
Before conducting a capacity discharge or commencing cycling, the
battery must be given a commissioning charge. In float applications
the commissioning charge shall consist of 7 continuous days of float
charge at the recommended float voltage (2.29Vpc at 20°C) with no
load connected to the battery. In hybrid applications the
commissioning charge shall consist of 24 hours charge at a voltage
equivalent to 2.40 Volts/cell with no load connected.
Float Operation
EON Technology® is designed for continuous float operation on
constant voltage chargers. Constant voltage charging is the safest,
most efficient and recommended method of charging VRLA batteries.
The recommended float voltage setting is 2.29Vpc at +20°C/+77°F.
Therefore the system voltage setting equals the number of cells in
series x 2.29Vpc.
Battery life and charging characteristics are affected by temperature.
Optimum battery life will be achieved when the battery is operating
between +20°C/+68°F and +25°C/+77°F (see figure 2).
Float Life
(Float @ 55°C Using Recommended FV for 20°C)
Float Charging Current Limit
Due to the very low internal resistance, PowerSafe® SBS® EON
Technology monoblocs and cells will accept unlimited current during
recharge but for cost and practical purposes in float applications
where recharge time to repeat duty is not critical, the rectifier current
can be limited to the load plus 0.1C10 Amps.
Fast Charging Operation
In addition to the long life characteristics inherent in traditional
PowerSafe® SBS TPPL battery designs, EON Technology® monoblocs
and cells have been developed to provide high performance in
applications where the battery is subjected to repeated cyclic duty, in
challenging operating conditions (high temperatures, unreliable grids,
remote locations, etc).
Fast charge techniques are best utilised for frequent discharge cyclic
applications. The high charge acceptance of EON Technology is suited
for applications which require a faster recharge with reduced time to
repeat duty. In such applications the rectifier voltage should be set at
2.40Vpc at 20°C. Figure 5 illustrates the time to full state of charge
from varying depths of discharge (C10) as a function of charge voltage.
Recharge Time to 100% State of Charge following C10 Discharge
to Varying Depths of Discharge.
Compare Float Charge with EON Technology® Recharge Regime
(Current Limit 25% C10)
0
1
2
3
4
5
6
7
8
9
% Depth of Discharge (C10)
Nominal Capacity (%)
Temperature compensation is capped at +40°C/+104°F as at this
temperature the compensated charge voltage approaches the natural
open circuit voltage of the battery and there is insufficient overvoltage
to keep the battery in a fully charged condition.
Float Voltage Temperature Correction
Monoblocs and cells must be given a freshening charge when the
OCV approaches the equivalent of 2.10 Volts per cell or when the
maximum storage time is reached, whichever occurs first.
120
110
100
90
80
70
60
50
40
30
20
10
0
The recommended float voltage temperature compensation is:
• 2.29Vpc +4mV per cell per °C below 20°C
• 2.29Vpc -4mV per cell per °C above 20°C
(refer to figure 4 for further details)
10 11 12 13 14 15 16 17
Calculated Life (Years @ 20°C)
Figure 2
Battery life is reduced by 50% for every 10°C/18°F increase in
temperature (see figure 3). Float voltage compensation reduces the
charging current as battery temperature increases and partially
negates the adverse effect of high temperature.
Service Life as a Function of Temperature
(Continuous Float Operation - Uncompensated FV)
110
100
90
80
70
60
50
40
30
20
10
0
EON Technology Fast Charge
0
2
8
10
12
14
16
As with float charge, temperature compensation for voltage is
applicable to fast charge techniques. The profile below (figure 6) gives
the recommended compensation to charge voltage for temperature.
Fast Charge Temperature Correction
15.00
14.00
2.53
13.00
2.51
12.00
2.49
11.00
2.47
10.00
2.45
Volts Per Cell
Service Life (Years)
6
Time to 100% State of Charge (Hrs)
Figure 5
16.00
9.00
8.00
7.00
6.00
5.00
4.00
2.43
2.41
2.39
2.37
2.35
2.33
3.00
2.31
2.00
2.29
1.00
2.27
0.00
15
Figure 3
4
FV Recharge
20
25
30
35
40
45
50
55
60
65
70
2.25
10
Temperature (ºC)
Figure 6
15
20
25
30
35
40
45
50
Temperature (°C)
3
Recharge time (hrs) = 2* ((0.8 x discharged Ah) / current limit) +1
Fast Charging Current Limit
In addition to the influence of charge voltage, the available charge
current will impact on time to repeat duty. The low internal resistance
of PowerSafe® SBS® EON Technology® monoblocs and cells lends
itself to absorption of unlimited in rush currents but can also be
recharged with current limits equal to the standing load plus 0.1C10
Amps.
Figure 7 illustrates the typical time to full state of charge (2.40Vpc) as
a function of available charge current from varying depths of
discharge.
Fast Charge Cycling
The high charge acceptance of PowerSafe SBS EON Technology
monoblocs and cells that enables the use of fast charge techniques
provides the user with the advantage of reduced time to repeat duty
and further extends the number of cycles available during service life
to unparalleled levels (figure 9).
Fast ChargeF Cycle as a Function of Depth of Discharge
9000
8500
8000
7500
7000
6500
Number of Cycles
In systems where control of charge factor is not possible, it may be
possible to estimate time to full state of charge by using the
calculation:
6000
5500
5000
4500
4000
3500
3000
2500
Time to Full State of Charge
TIME TTO
FULLL SSTATE
O FFUL
TAATE OF CHARGE
CHAR
RGE
As a Function
of CURRENT
Current
Limit
and
Depth of0Vpc
Discharge
LIMITT AND DEPTH OFF DISCHARGE at 2.40Vpc
AS A FUNCTION
FUNC
CTION OF CURREN
T LIMI
(Recharge 2.40Vpc)
2000
1500
1000
500
0
18
10
25
30
35
40
45
50
55
60
65
70
% Depth of Discharge
0.3C10 Ampss
12
0.5C10 Ampss
1C10 Amps
10
0.2C10A
8
0.3C10A
6
0.5C10A
4
1C10A
2
0
0%
10%
20%
30%
40%
50%
60%
%
70%
80%
800%
90%
100%
110%
DEPTH
DISCHARGE
RGE
Depth
ofOFDischarge
Figure 7
Cycling
Float Cycling
EON Technology has been developed to retain the long float life
characteristics associated with standard PowerSafe SBS Technology
and has the added capability to deliver high performance in harsh
applications where cyclic duty predominates.
The optimal cyclic performance shown in figure 9 is based on the
battery being returned to full state of charge between cycles. It is
possible to operate SBS EON Technology monoblocs and cells in
controlled partial state of charge condition to improve site operating
expenditure savings, however it is very important to ensure that the
battery is periodically returned to full state charge to ensure that the
battery does not suffer from reduced performance due to the build up
of irreversible sulphation. It is recommended to contact your
EnerSys® representative to obtain additional information and
guidance for such PSOC applications.
Extensive testing has shown that in traditional float cyclic
applications PowerSafe SBS EON Technology surpasses the excellent
performance of standard PowerSafe SBS battery designs, typically
delivering a 33% increase in the number of cycles during evaluation
to international benchmark standards (figure 8).
SBS EON Technology delivers superior performance in grid assist
float applications where mains power supply can be semi stable or in
applications where power outages can be frequent and unscheduled
leading to risk of uncontrolled partial state of charge cycling.
F
Float Cycle Life as a Function of Depth of Discharge
3000
2800
2600
2400
Number of Cycles
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
0
10
20
Figure 8
www.enersys-emea.com
30
40
50
60
70
80
% Depth of Discharge
EnerSys
World Headquarters
2366 Bernville Road
Reading, PA 19605
USA
Tel: +1 610 208 1991
+1 800 538 3627
Fax: +1 610 372 8613
EnerSys EMEA
EH Europe GmbH
Löwenstrasse 32
8001 Zürich
Switzerland
EnerSys Asia
152 Beach Road
Gateway East Building
Level 11
189721 Singapore
Tel: +65 6508 1780
Contact:
© 2013 EnerSys. All rights reserved.
Trademarks and logos are the property of
EnerSys and its affiliates unless otherwise noted.
Publication No: EN-SBS-EON-AG-006 - December 2013 - Subject to revisions without prior notice. E.&O.E.
Time
(HRS)
TIME(Hours)
(HR
RS)
20
Figure 9
0.2C10 Ampss
14
15
0.1C10A
0.1C10 Ampss
16