EnerSys Genesis EP, Genesis XE User manual
XE & EP BATTERIES
APPLICATION
MANUAL
RESERVE
POWER
Genesis®XE & EP Application Manual
TABLE OF CONTENTS
Preface 2
Chapter 1: Introducing the Genesis
®
Battery 3
1.1 Background 3
1.2 Transportation classification 3
1.3 UL component recognition 3
1.4 Non-halogenated plastics 3
1.5 Key Genesis benefits 3
Chapter 2: Technical Information 4
2.1 Introduction 4
2.2 Choosing the right Genesis version 4
2.3 Battery life 4
2.4 Constant-power and constant-current discharge performance 5
2.5 Charging characteristics & requirements 6
2.6 Constant-voltage (CV) regime 7
2.7 Constant-current (CC) regime 7
2.8 Three-step (IUU) charge profile 8
2.9 Storage characteristics 9
2.10 Self discharge 9
2.11 Open circuit voltage (OCV) and state of charge (SOC) 10
2.12 Procedure to recover overdischarged batteries 10
Chapter 3: General Test Data 11
3.1 Introduction 11
3.2 Thermal runaway test 11
3.3 Gassing test 11
3.4 DIN standard overdischarge recovery test 12
3.5 High temperature storage recovery test 12
3.6 Altitude test 12
3.7 Accelerated float life test 12
3.8 Performance test at different temperatures 13
Chapter 4: Installation, Operation & Maintenance 13
4.1 Introduction 13
4.2 Receiving the shipment 13
4.3 Storage 13
4.4 Installation 13
4.4.1 Temperature 14
4.4.2 Ventilation 14
4.4.3 Security 14
4.4.4 Mounting 14
4.4.5 Torque 14
4.5 Parallel strings 14
4.6 Discharging 14
Appendix A: Genesis
®
XE Discharge Characteristics 15-24
Appendix B: Genesis
®
EP Discharge Characteristics 25-31
Preface
This European edition of the
Genesis Application Manual
introduces the Genesis XE range
of batteries, packaged to offer
the same superior performance
characteristics as the Genesis EP
battery in more physically
demanding applications such as
high temperature and high
vibration environments.
Appendix A offers constant
current (CC) and constant power
(CP) performance data and
graphs for the full range of
Genesis XE batteries to several
end voltages. Appendix B offers
the same information for the EP
series.
Chapter 4 offers guidelines on
the installation, operation and
maintenance of Genesis
batteries, with the goal of
maximising performance and
service life.
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Chapter 1:
Introducing the Genesis Battery
1.1 Background
Since its introduction in the early 1990s, the Genesis
®
thin plate pure lead-tin (TPPL) battery has established
itself as a premium high performance battery suitable for
a wide range of demanding applications. Today, TPPL
technology can be found in applications as diverse as
emergency power, avionics, medical, military and
consumer equipment.
The Genesis TPPL battery is offered in either the EP or
XE version, and Table 2.2.1 shows the differences
between the two versions.
1.2 Transportation classification
Effective September 30, 1995, Genesis batteries were
classified as "nonspillable batteries", and are excepted
from the Department of Transportation’s comprehensive
packaging requirements if the following conditions are
satisfied:
(1)
The battery is protected against short circuits
and is securely packaged and
(2)
The battery and outer
packaging must be plainly and durably marked
"NONSPILLABLE" or "NONSPILLABLE BATTERY".
Genesis batteries have been tested and determined to be
in compliance with the vibration and pressure differential
tests contained in 49 CFR § 173.159(d).
Because Genesis batteries are classified as
"Nonspillable" and meet the conditions above, [from §
173.159(d)] they do not have an assigned UN number
nor do they require additional DOT hazard labelling.
1.3 UL component recognition
All Genesis batteries are recognised as UL components.
1.4 Non-halogenated plastics
As the world becomes more environmentally aware,
EnerSys
®
is striving to provide the most environmentally
friendly products possible. With this in mind, we are
proud to say that the plastics used in our Genesis
product line are non-halogenated and therefore do not
contain any of the following materials:
Polybrominated biphenyls (PBB)
Polybrominated biphenyl ethers (PBBE)
Polybrominated biphenyloxides (PBBO)
Polybrominated diphenyl ethers (PBDPE)
Polybrominated diphenyl oxides (PBDPO)
Tetrabromobisphenol-A (TBBA)
Deca-bromo biphenyl ethers (DBBPE’s).
The battery meets the non-halogenated flame retardancy
requirements of UL 94V-0 by using plastics with nonhalogenated flame retardants. Finally, the plastic material
used in the manufacturing of Genesis batteries is in full
compliance with the German Dioxin Ordinance of 1994.
1.5 Key Genesis benefits
Table 1.5.1 lists some of this battery’s features and
benefits. The Genesis battery is well suited for any
application - high rate, low rate, float or deep discharge
cycling.
Chapter 1:
Introducing the Genesis®Battery
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Feature Benefit
High volumetric and gravimetric power densities More power in less space and weight
Thin-plate design Superior high rate discharge capability
Low internal resistance Flatter voltage profile under high-rate discharge;
excellent low temperature performance
1
Negligible gassing under normal charge Safe for use in human environments such as offices and
hospitals. Must be installed in non-gastight enclosures
100% maintenance-free terminals True fit-and-forget battery
Flexible mounting orientation Battery may be installed in any position except inverted
Rugged construction Tolerant of high shock and vibration environments, especially the
XE version
Advanced manufacturing techniques High reliability and consistency
Very high purity lead-tin grid Lower corrosion rates and longer life
Non-halogenated flame retardant case and cover Meets UL 94 V-0 requirement, with an LOI >28%
Excellent high-rate recharge capability Allows >95% recharge in under an hour
Low self-discharge Longest shelf life among VRLA batteries (2 years at 25ºC)
Wide operating temperature -40ºC to +80ºC
Table 1.5.1: Key features and benefits of the Genesis battery
1 See Table 2.4.1 and Figure 2.4.1 in Section 2.4 of Chapter 2
2 The XE version of the Genesis battery may be used at 80ºC when fitted with a metal jacket
2.3 Battery life
The life expectancy of a Genesis battery depends on the
specific application. It is expressed in terms of either
cycles or years. While life in years is self-explanatory,
a cycle refers to a sequence in which a charged battery is
discharged and then charged back up. One complete
sequence constitutes one cycle. In general, if the battery
is to be discharged frequently, cycle life rather than
calendar life is more relevant. On the other hand, if the
battery is to be used primarily as power backup, calendar
life of the battery should be considered.
In situations where one is not quite sure whether the
application is cyclic or standby (float), the following
criteria may be used to determine the application
category:
If the average time on charge between two successive
discharges is thirty (30) days, the application may be
considered to be of a standby (float) nature.
The minimum time between two successive
discharges must not be less than fourteen (14) days.
If either of these two criteria is not satisfied, the
application should be considered cyclic.
Chapter 2:
Technical Information
2.1 Introduction
We have divided this chapter into small sections
allowing you to locate the information quickly and
easily.
2.2 Choosing the right Genesis
®
version
As mentioned before, the Genesis
®
pure lead-tin
battery is available in EP and XE versions.
The EP battery is adequate under most operating
conditions.
Special application situations such as high ambient
temperature or high shock and vibration require the
XE version.
Table 2.2.1 summarises the differences between the
two versions and is designed to help you choose the
right version for your application. In this table, the
differences are highlighted in red boldfaced.
Feature Genesis®EP Genesis®XE
Technology Pure lead-tin absorbed glass mat (AGM)
Float life @ 2.27 volts per cell (Vpc) charge 10 years @ 25ºC 12 years @ 25ºC
Cycle life 400 to 80% depth of discharge (DOD)
Shock & vibration tolerance Good Better
Operating temperature range • -40ºC to +45ºC • -40ºC to +45ºC
• -40ºC to +60ºC • -40ºC to +80ºC
with metal jacket (denoted EPX) with metal jacket (denoted XEX)
Shelf life @ 25ºC 2 years from 100% charged down to 12V per block
Capacity @ 10-hr. rate 100% (reference) ≈ 95%
Weight 100% (reference) ≈ 105%
Dimensions Same footprint
Quick charge 6C to 8C charge acceptance at 25ºC
Overdischarge abuse tolerance Exceeds DIN standard for overdischarge recovery
High-rate discharge 100% (reference) ≈ 95%
Flame retardant rating V-0 rated case and cover
Case & cover colour Black Orange
Shipping Air shippable with no restrictions
Table 2.2.1: Choosing the right Genesis
®
version
Chapter 2:
Technical Information
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While several factors affect the life of a battery, cycle life
depends primarily on the depth of discharge (DOD). At a
DOD of 80%, the Genesis
®
battery will deliver 400 cycles;
at 100% DOD, that number decreases to 320 cycles
All cycle life estimates assume adequate full recharge.
Figure 2.3.1 shows the relationship between DOD and
cycle life.
Figure 2.3.1: Cycle life and depth of discharge (DOD)
In contrast to cycle life, ambient temperature
dramatically affects float life. For roughly every 8°C rise
in ambient temperature above 25ºC, the float life of a
VRLA battery is cut in half. In other words, a 10-year
battery at 25°C) is only a 5-year battery at 33°C.
Additionally, float life is cut in half for every 100mV per
cell over the recommended float charge voltage.
The relationship between ambient temperature and
expected float life is given by the Arrhenius equation.
The equation defines the relationship between the
ambient temperature and the rate of internal positivegrid corrosion of the battery, which is the normal process
of battery aging.
A key point to note is that the temperature in question is
the battery ambient temperature. If the system is in a
25°C environment and the battery is installed next to a
power transformer where the temperature averages
32°C, then all battery calculations must be based on
32°C.
The Arrhenius equation is the theoretical foundation for
the relationship used in practice to derive the
acceleration factor for a given temperature. The equation
is shown below, in which AF is the acceleration factor
and T is the battery ambient temperature in ºC.
As an example, consider a battery in a float application
at an ambient temperature of 37ºC. Replacing T with 37
in the equation above the acceleration factor (AF) in this
case would be 2
(1.5)
or 2.83. A 10-year battery in this
situation should be expected to last only about
3.5 years (10/2.83 =3.5). Figure 2.3.2 graphically shows
the relationship between temperature and float life for
the EP and XE series batteries, assuming temperature
compensation and a reference temperature of 25ºC.
Figure 2.3.2: Battery temperature and float life
2.4 Constant-power and constant-current discharge
performance
Batteries are generally required to support either
constant-power (CP) or constant-current (CC) loads.
CP and CC discharge curves are provided in Appendix A
for Genesis
®
XE and in Appendix B for Genesis EP
batteries. The information is provided in both tabular and
graphical formats, with each curve representing the
discharge profile for a specific model to a specific end
voltage.
If intermediate run times are required, such as
watts per
battery
for 7 minutes to 1.67 volts per cell, the graphs
may be used to estimate the
watts per battery
available.
Generally speaking, most battery systems for indoor
applications are in temperature-regulated environments.
However, there are occasions when this is not the case.
This can happen when the batteries are installed in close
proximity to heat generating sources such as
transformers. In such cases, the user should know what
kind of life to expect from the batteries, since it is well
established that a battery’s overall life is sensitive to
ambient temperature.
In addition to the dependence of battery life on ambient
temperature, battery capacity also varies with
temperature. Table 2.4.1 shows the variation in battery
capacity as a function of the ambient temperature.
The capacity at 25ºC is taken as 100%.
(0.125T-3.125)
AF = 2
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1000000
Charge profile:
CV@2.45 VPC for 16 hours
100000
10000
Current limit at 1C
100
10
1
Years to 80% capacity
Genesis EP Genesis XE
Nunmber of cycles
1000
100
10
0
30
20
50
40
Depth of discharge, DOD%
60
70
90
80
100
0
20
15
30 35
25
40 45
Temperature, °C
55
60
50
65
Temperature -20ºC 0ºC 25ºC 40ºC 55ºC
Capacity @
15 min. rate 65% 84% 100% 110% 120%
Table 2.4.1: Effect of temperature on 15-minute discharge
A graph of capacity as a function of temperature for the
Genesis
®
battery is shown in Figure 2.4.1 for various
rates of discharge.
Figure 2.4.1: Capacity as a function of temperature
Although the Genesis battery may be used, with
appropriate derating, from -40°C to 80°C, it is strongly
recommended that every effort be made to install them
in temperature-regulated environments. Metal jackets are
required for temperatures exceeding 45°C continuous.
All battery temperatures refer to the temperatures
experienced by the active materials
inside
the battery.
The time required by the active materials to reach
thermal equilibrium within the battery environment may
be considerable.
2.5 Charging characteristics & requirements
A constant-voltage (CV) regime is the preferred method
of charging these batteries, although a constant-current
(CC) charger with appropriate controls may also be used.
There is no limit on the magnitude of the charge current
during a CV charge. Because of the Genesis battery’s low
internal resistance, it is able to accept any level of inrush
current provided by a constant-voltage charger.
Note:
The following paragraphs on battery
charging have been considerably simplified for better
understanding. For example, no account has been
taken of the polarisation voltage. Second, the
battery resistance has been assumed to be static.
This is a simplifying assumption since the battery’s
internal resistance will change continuously during
the charge cycle.
This dynamism in the internal resistance occurs because
of the changing state of charge and the fact that the
temperature of the active materials within the battery is
dynamic.
Owing to these simplifications, the current magnitudes
obtained in the sample calculations are exaggerated.
However, if one remembers that assumptions have been
made and that the
mathematical steps are for illustration
only
, then the actual current values calculated become
immaterial.
It is known from basic electric-circuit theory that the
current in any circuit is directly proportional to the
voltage differential in the circuit (Ohm’s Law). Therefore,
as charging continues at a constant voltage, the charging
current decreases due to the decreasing difference
between the charger-output voltage and the batteryterminal voltage. Expressed differently, the charging
current is at its highest value at the beginning of the
charge cycle and at its lowest value at the end of the
charge cycle.
Thus, in a CV charge circuit, the battery is the current
regulating device in the circuit. It will draw only that
amount of current as necessary to reach full charge.
Once it attains 100% state of charge, it continues to draw
small currents in order to compensate for
standing/parasitic losses.
Assume that the battery under consideration has an
internal resistance of 4mΩ (0.004Ω) when fully charged.
Also, assume that it has an internal resistance of 8mΩ
(0.008Ω) when discharged to an end voltage of 10.5
volts. However, the instant the load is removed from the
battery, its voltage jumps back up to 12 volts, and this is
the initial back electromotive force (EMF) the charger
output terminals will see. The influence of this voltage
on the charge-current inrush is illustrated in the initial
and final charging magnitudes.
It is now decided to recharge the battery at a constant
voltage of 2.27 volts per cell or 13.62 volts per battery.
Further, assume that when the battery reaches a state of
full charge, the internal resistance reduces to 4mΩ and
the terminal voltage rises to 13.60V.
For illustrative
purposes, this final end-of-charge terminal voltage has
been kept deliberately slightly lower than the charging
voltage.
In reality, the charging process is dynamic. As soon as a
charging source is placed across the terminals of a
discharged battery, its voltage begins rising in an
attempt to match the charger-output voltage. Given
enough time, one would expect that the battery voltage
at some point would exactly equal the charger voltage,
thereby reducing the voltage difference in the charging
circuit to zero and thus forcing the charge current to
zero. However, this does not happen because of the
internal electrochemistry, which ensures that the battery
will keep drawing small charging currents even when
fully charged.
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10
1
0.1
Discharge time, hours
0.01
-30
-40
15 min. rate
-20
-10 0
Temperature, °C
IC rate 0.2C rate
10
30
20
40
However, almost immediately, the battery selfdischarges, depressing its terminal voltage below the
charger voltage, thereby initiating a current flow once
again. The entire process, as outlined in the previous
paragraph, will then repeat itself.
Applying Ohm’s Law, which states that
the current in a
circuit is equal to the voltage gradient (difference) in the
circuit divided by the total resistance in the circuit
, and
substituting the various parameters’ assumed values,
we have the following charging currents. Note that all
connection resistances, such as those for cables, are
neglected for simplicity. This omission does not affect
the outcome since its influence would be the same in
both cases, neglecting changes due to electrical heating.
Initial charging current = = 202.5A
Final charging current = = 5A
This example shows how the battery acts as a current
regulator in a CV charge circuit, decreasing the current
flow in the circuit to suit its own state of charge.
Thus, even if the current limit on the charger were
250 amperes, the battery would see an inrush current of
202.5 amperes, before it tapered off and finally dropped
to its lowest value at the end of the charge cycle.
Although the 250A figure is impractical because of
prohibitive charger costs, it serves to drive home the
point that as far as the battery is concerned, a specific
current limit is not necessary for Genesis
®
batteries
under CV charging. In reality, the current limit would be
dictated by a combination of technical and economic
considerations. Note also that, in general, most other
battery manufacturers recommend current limits based
on battery capacity, usually 0.25C
10, where C10 is the
10-hour rating.
Increasing the current limit will reduce the total recharge
time, but at greater cost. The reduction in recharge time
occurs mainly up to the 90% state of charge level; the
impact on total recharge time is much less. The chargeroutput voltage exercises a much greater influence on the
total recharge time.
The question then becomes whether the reduction in the
time needed for a recharge can justify the additional
costs. In some critical applications, this may be the case,
while in other situations the added cost may not be
justifiable.
The time to recharge a battery under float charge is
shown in Figure 2.5.1. The graphs show the time taken
to reach three different states of charge. For example,
with a charge current of 0.2C
10 amps the battery will get
to 100% SOC in about 12 hours when charged at 13.62V
(2.27 Vpc).
Figure 2.5.1: Recharge times under float charge
2.6 Constant-voltage (CV) regime
In a float or standby application the CV charger should
be set at 13.5V to 13.8V at 25ºC. For a cyclic application,
the charge voltage should be set between 14.4V and 15V
at 25ºC. In both cases, the linearised temperature
compensation factor is ±24mV per battery per ºC
variation from 25ºC. The higher the temperature the
lower the charge voltage should be and vice versa.
Figure 2.6.1 shows the temperature compensation factor
for float and cyclic applications. Equations representing
the compensation curves are also shown in this figure.
Note that for both types of application there is no limit
on the inrush current. We recommend the highest
practical and economical current limit possible.
Figure 2.6.1: Temperature compensation graph
2.7 Constant-current (CC) regime
Unlike CV charging, CC charging requires the charge
current to be limited to 0.33C
10 to avoid damaging the
battery. Once 100% of previously discharged capacity
has been returned the overcharge should be continued
at a much lower rate, such as 0.002C
10, i.e., at the
500-hour rate.
13.62 - 12.00
0.008
13.62 - 13.60
0.004
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80% SOC
25
20
15
10
Time in hours at 2.27 VPC & 25°
5
0
0
0.2
Recharge current in multiple of rated capacity
90% SOC
0.4 0.6
100% SOC
0.8 1
2.90
2.80
2.70
2.60
2.50
2.40
Theoretical float (ideal)
Charge voltage, Vpc
2.30
V = 0.00004T
and 2.20VPC minium
2.20
2.10
-40
-30 -20
Theoretical cycling (ideal)
V = 0.00004T
2
- 0.006T + 2.3945
-10 0
2
- 0.006T + 2.5745
10
20
Temperature, °C
30
40
50 60
70 80
When using a CC-charge regime, the charge current
must switch from a high (starting) rate to a low
(finishing) rate when the battery reaches 100% state of
charge. The point at which this switch occurs may be
determined by using a timer or by sensing the battery
voltage.
The timer setting can be determined by calculating the
time needed to return 105% to 110% of the amperehours drawn out. However, this method should not be
used unless the previously discharged capacity can be
reliably and consistently measured.
Alternatively, the battery-terminal voltage can be used to
trigger the transition from a high charge current to a low
charge current. As the battery charges up, its voltage
reaches a peak value and then begins to decline to the
steady-state, fully charged value. The point at which this
drop (point of inflection) begins depends on the charge
current’s magnitude, as shown in Figure 2.7.1. Since the
charge voltages in Figure 2.7.1 are on a per cell basis,
simply multiply the numbers by 6 as all Genesis
®
batteries are 12V units.
The inflection point may be used to switch the current
from a high rate (≤ 0.33C
10) to a low rate (≈0.002C10).
This is a more reliable method than amp-hour counting,
as it is independent of the previously discharged
capacity.
Figure 2.7.1: CC charging curves at 25ºC
The Genesis battery may be recharged using either a
constant-current (CC) or constant-voltage (CV) charger,
although the CV regime is the preferred method
. This
flexibility in the charging scheme is an advantage, since
it is easy for the user to replace existing batteries with
Genesis without having to alter the charging circuitry.
Because of the thin plate pure lead-tin technology used
in this battery, the internal resistance is significantly
lower than that of conventional VRLA batteries. For
example, the 26EP battery has an internal resistance of
about 5mΩ when fully charged. This compares very
favourably with a typical value of 10 to 15mΩ for
competitive products of equal capacity.
The low internal resistance helps the Genesis battery
accept large inrush currents without any harmful effects.
The heat generated by the charge current is kept at a low
level because of the very low internal resistance value.
The very high recharge efficiency of this battery also
allows high inrush currents. In tests performed on the
26Ah product, the initial current drawn by the battery
was 175 amperes. The Genesis battery may be recharged
much more rapidly than conventional VRLA batteries
because of its ability to safely accept very high currents.
Table 2.7.1 demonstrates this quick charge capability
when using a CV charge of 14.7V.
Table 2.7.1: Inrush current and charge time
This fast-charge capability is remarkable in a VRLA
battery. This feature makes the Genesis battery
competitive with a nickel-cadmium battery, which
traditionally had an advantage over lead acid batteries
due to its short charge times.
The quick charge capability of the Genesis battery makes
it particularly suitable for applications where the battery
has to be returned quickly to a high state of charge after
a discharge.
2.8 Three-step (IUU) charge profile
A three-step charge profile developed for use with the
Genesis TPPL battery is shown in Figure 2.8.1. The first
step (bulk charge) is a constant current (CC) charge with
a minimum current of 40% of the 10-hour (C
10) rating of
the battery. For example, to use this profile effectively on
the 16Ah battery, the minimum charge current must be
6.4 amps.
Bulk charge continues until the battery voltage reaches
14.7V. The charger then switches to a constant voltage
(CV) mode at 14.7V and the absorption charge phase
begins.
The charger switches to the temperature-compensated
float phase when either the current drops to 25% of the
bulk charge current (0.1C
10 amps) or the time in the
absorption phase reaches 8 hours, whichever occurs
first.
If the charger has a timer override so that the absorption
phase does not exceed 8 hours, the threshold current at
which the charger switches from absorption phase to
float phase should be reduced to 0.001C
10. This equals
16mA for the 16Ah battery discussed in the earlier
example.
If the charger does not have a timer the trigger to switch
from absorption phase to float phase should be set at
0.1C
10.
Magnitude of inrush current
Capacity
returned 0.8C
10
1.6C
10
3.1C
10
60% 44 min. 20 min. 10 min.
80% 57 min. 28 min. 14 min.
100% 1.5 hrs. 50 min. 30 min.
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Voltage Profiles at 25C
C/5
5
Constant Current Charging
C/15
C/10
10
Time (Hours)
C/20
2015
3025
Voltage
3
2.8
2.6
2.4
2.2
2
1.8
0
Note:
The battery will not be fully charged when a
switch from absorption to float charge is made when
the current drops to 0.1C
10
. The battery will need a
minimum of 16-24 hours on float charge before it is
fully charged. The battery may be used as soon as
the switch to float is made, but repeatedly cycling it
without the necessary 16-24 hours’ on float charge
will cause premature failure of the battery.
Alternatively, the charger can stay in the absorption
phase for a fixed 8 hours. Once this absorption charge
time is over, the charger can switch to a temperaturecompensated float voltage. The advantage with this
design is a less complex circuit because it is not
necessary to monitor the charge current in the
absorption phase.
Table 2.8.1 lists the different IUU charge profile options.
A check mark indicates the feature is available in the
charger, while X indicates a charger that does not have
the feature. Note that all three designs have bulk,
absorption and float charge phases. The differences
between the three designs are limited to (a) whether a
timer is available, (b) whether the circuit monitors the
charge current and (c) the magnitude of the threshold
current, if it is used to trigger the switch from absorption
charge to float charge.
Table 2.8.1: IUU charger design options
Design 1:
The charger has a timer and a current threshold that
triggers the switch from absorption charge to float
charge. Since the timer is present, the trigger current is
set low. If the current does not drop to 0.001C
10
amps
within 8 hours on absorption charge, the timer will force
the switch to a temperature-compensated float charge.
Design 2:
The charger does not switch to a float charge based on a
preset charge current. Rather, the timer stays in the
absorption phase for 8 hours before switching to a
temperature-compensated float charge.
Design 3:
The charger has no timer. Since switching depends
solely on the charge current dropping to a set level, the
threshold is set high enough to ensure the charger will
always switch to a float charge. In this design the battery
will not be fully charged at the start of the float charge.
A minimum of 16-24 hours on float will be required to
complete the charge.
Figure 2.8.1: Three-step (IUU) charge profile
2.9 Storage characteristics
Improper storage is a common form of battery misuse.
High storage temperature and inadequate frequency of
freshening charges are examples of improper storage.
In order to better understand the various mechanisms
influencing sealed-lead batteries kept in storage, the
following paragraphs discuss in general terms several
aspects of the batteries’ storage requirements.
2.10 Self discharge
All batteries lose charge over time when kept on open
circuit. This phenomenon is termed
self-discharge
.
If the capacity loss due to self-discharge is not
compensated by recharging in a timely fashion, the
capacity loss may become irrecoverable due to
irreversible sulphation, where the active materials (PbO
2,
lead dioxide, at the positive plates and sponge lead at
the negative plates) are gradually converted into an
electroinactive form of lead sulphate, PbSO
4. If the
capacity loss associated with self-discharge is not
replenished, the battery ultimately fails because storage
is electrochemically equivalent to a very low rate of
discharge.
Storage temperature is the key factor influencing the
self-discharge rate because it plays a major role in
determining the speed at which the internal chemical
reaction proceeds. The higher the temperature, the faster
the speed of chemical reactions.
Design 1 ✓✓✓0.001C10
amps ✓
Design 2 ✓✓✓X ✓
Design 3 ✓✓X 0.10C
10
amps ✓
Feature
Bulk Absorption Timer Trigger Float
9
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Bulk charge
Voltage
(RED)
NOTES:
1. Charger LED stays RED in bulk charge phase (DO NOT TAKE BATTERY OFF CHARGE)
2. LED changes to ORANGE in absorption charge phase (BATTERY AT 80% STATE OF CHARGE)
3. LED changes to GREEN in float charge phase (BATTERY FULLY CHARGED)
4. Charge voltage is temperature compensated at ±24mV per battery per ºC variation from 25ºC
8-hour absorption charge
(ORANGE)
Charge voltage
Charge current
14.7V
Continuous float charge
(GREEN)
13.6V
0.4C
Amps
10 min
Just as every 8°C rise in operating temperature cuts the
battery’s life expectancy in half, so does every 8°C
increase in ambient temperature reduce the storage life
of a battery by 50%. Conversely, a reduction in storage
temperature will have the reverse effect by increasing
the allowable storage time.
2.11 Open circuit voltage (OCV) and state of charge
(SOC)
Since most batteries are subject to some kind of storage,
it is important for the user to have some method of
accurately estimating the battery capacity after it has
been in storage.
Figure 2.11.1: Open circuit voltage and state of charge
Although efforts should be made to ensure that batteries
are stored in temperature-controlled environments, a
freshening charge should be applied once every twentyfour (24) months or when the open-circuit voltage (OCV)
reading drops to 12V, whichever comes first. As shown
in Figure 2.11.1, 12V corresponds to a 35% state of
charge (SOC).
The battery may be permanently
damaged if the OCV is allowed to drop below 11.90V
.
Figure 2.11.1 shows the OCV and corresponding SOC for
a Genesis battery. An OCV of 12.84V or more indicates a
battery at 100% SOC. The figure is accurate to within
20% of the true SOC of the battery
if the battery has not
been charged OR discharged in the 24 hours preceding
the voltage measurement
. The accuracy improves to 5%
if the period of inactivity before the voltage
measurement is 5 days.
Capacity loss during storage is an important
consideration, particularly in applications where
performance loss due to storage is unacceptable.
However, knowing how much charge is remaining in the
battery at any point in its storage life is equally
important as the battery must be maintained at a
minimum charge level in order to prevent permanent
damage. Figure 2.11.2 shows the relationship between
storage time and remaining capacity at 25ºC, 45ºC and
65ºC.
Figure 2.11.2: Storage capacity at temperatures
2.12 Procedure to recover overdischarged batteries
There may be instances when a Genesis
®
battery is
overdischarged to the point where a standard charger is
unable to fully recharge the battery. In such cases, the
following procedure may help recover the affected
battery.
1. Bring the battery to room temperature (25°C).
2. Measure the OCV. Continue to step 3 if it is at least
12V; otherwise terminate the procedure and reject the
battery.
3. Charge the battery using a 0.05C
10 constant current for
24 hours. The charger should be capable of providing
a driving voltage as high as 36V. Monitor the battery
temperature;
discontinue charging if the battery
temperature rises above 45ºC
.
4. Allow the charged battery to stand on open circuit for
a minimum of 1 hour before proceeding to Step 5.
5. Perform a capacity test on the battery and record the
amp-hours delivered. The longer the discharge the
more reliable the result. This is Cycle 1.
6. Repeat steps (3) to (5). The capacity returned in step 5
is now Cycle 2. If Cycle 2 capacity is greater than Cycle
1 capacity proceed to step 7; otherwise reject the
battery.
7. Repeat steps (3) to (5) to get Cycle 3 capacity. Proceed
to step 8 if Cycle 3 capacity is equal to or more than
Cycle 2 capacity. Reject the battery if Cycle 3 capacity
is less than Cycle 2 capacity.
8. If Cycle 3 capacity equals or exceeds Cycle 2 capacity,
recharge the battery and put it back in service.
10
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100
90
80
70
25°C
45°C
65°C
13.0
12.8
12.6
12.4
12.2
12.0
Open circuit voltage (OCV), V
11.8
11.6
20 30 40 50 60 70 80 90 100
10
12.84V or higher indicates 100% SOC
State of Charge (SOC), %
60
50
Percent of 0.05C capacity
40
30
0
20
10
30 40
Open circuit storage time in weeks
60 70
50
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