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Hawker XT™ Application Manual

First Edition

Kalyan JanaWestern Product Support ManagerHawker Energy Products Inc.Warrensburg, MO 64093 - 9301 (USA)

© Hawker Energy Products Inc. 2First EditionApril 1999


Table of contents

Ch. 1: Introducing the Hawker XT™ battery.....................................................................................7

1.1 Introduction............................................................................................................................................7

1.2 Valve regulated design...........................................................................................................................7

1.3 Wide operating temperature range........................................................................................................8

1.4 High rate charge and discharge capabilities........................................................................................8

1.5 Long life in float applications................................................................................................................8

1.6 Advanced separator design....................................................................................................................8

1.7 Ability to operate under intermittent charging.....................................................................................9

1.8 Compliance with Bellcore and BS specifications .................................................................................9

1.9 Integral chimney and flash arrestor .....................................................................................................9

1.10 Superior internal packaging..............................................................................................................10

1.11 Integral handles .................................................................................................................................10

1.12 Flame retardant rating and lower oxygen index (LOI)....................................................................10

1.13 Transportation classification ............................................................................................................11

1.14 UL component recognition .................................................................................................................11

Ch. 2 : Hawker XT™ benefits ...............................................................................................................12

2.1 Introduction..........................................................................................................................................12

2.2 High discharge current ........................................................................................................................12

2.3 Low temperature operation..................................................................................................................12

2.4 Orientation flexibility...........................................................................................................................13

2.5 Recombinant VRLA design..................................................................................................................13

2.6 Shock & vibration characteristics .......................................................................................................15

2.6.1 MIL S-901C shock, high impact test............................................................................................15

2.6.2 MIL S-167-1 for mechanical vibrations.......................................................................................16

2.6.3 Vehicle vibration test ....................................................................................................................16

2.6.4 Three axis vibration test ...............................................................................................................17



2.7 Float life characteristics.......................................................................................................................17

2.8 Float/cyclic capability .........................................................................................................................18

2.9 Cycle life characteristics ......................................................................................................................19

2.10 Fast charging characteristics ............................................................................................................19

2.11 Storage characteristics.......................................................................................................................20

Ch. 3 : Discharging the Hawker XT™ battery .................................................................................21

3.1 Introduction..........................................................................................................................................21

3.2 Discharge voltage profile .....................................................................................................................21

3.3 Discharge level......................................................................................................................................23

3.4 Discharge characteristics.....................................................................................................................24

Ch. 4 : Hawker XT™ battery storage..................................................................................................35

4.1 Introduction..........................................................................................................................................35

4.2 State of charge and open circuit voltage .............................................................................................35

4.3 Storage ..................................................................................................................................................36

4.4 Overdischarge recovery characteristics ...............................................................................................38

4.4.3 German DIN standard test for overdischarge recovery ..............................................................38

4.4.4 High temperature (50°/122°F) discharged storage test ..............................................................39

Ch. 5 : Charging the Hawker XT™

battery ........................................................................................41

5.1 Introduction..........................................................................................................................................41

5.2 General..................................................................................................................................................41

5.3 Constant voltage (CV) charging ..........................................................................................................42

5.4 Fast charging or cyclic charging .........................................................................................................43

5.5 Cycling Hawker XT™ batteries with lower inrush.............................................................................45

5.6 Float charging and temperature compensation..................................................................................46

5.7 Constant current (CC) charging ..........................................................................................................47

Ch. 6 : Hawker XT™ battery service life ...........................................................................................49

6.1 Introduction..........................................................................................................................................49



6.2 Cycle life................................................................................................................................................49

6.3 Float life................................................................................................................................................50

6.4 Float life estimation based on actual temperatures ...........................................................................51

Ch. 7 : Safety issues ................................................................................................................................53

7.1 Introduction..........................................................................................................................................53

7.2 Gassing .................................................................................................................................................54

7.3 Shorting ................................................................................................................................................55



List of tables & figuresList of tables & figuresList of tables & figuresList of tables & figures

Figure 2.3-1 : Variation of capacity with temperature .............................................................................13

Figure 2.8-1 : Hawker XT™ cycling at 13.62V at 25°C ............................................................................19

Figure 3.2–1(a) : Medium rate discharge voltage profile .........................................................................22

Figure 3.2–1(b) : High rate discharge voltage profile...............................................................................22

Table 3.3-1 : Recommended battery EODV...............................................................................................23

Figure 3.4-1 : Hawker XT™ 13Ah performance data to 10.5V (1.75 VPC) .............................................25

Figure 3.4-2 : Hawker XT™ 13Ah performance data to 10.02V (1.67 VPC) ...........................................26








Figure 3.4-10 : Hawker XT™ 70Ah performance data to 10.02V (1.67 VPC) .........................................34

Figure 4.2-1 : Variation of OCV with state of charge ...............................................................................35

Figure 4.3-1(a) : Capacity degradation during storage at 25°C ..............................................................36

Figure 4.3-1(b) : Capacity degradation during storage at 45°C ..............................................................37

Figure 4.3-1(c) : Capacity degradation during storage at 65°C...............................................................37

Figure 4.4.4-1 : Recovery of Hawker XT™ batteries from discharged storage at 50°C ..........................40

Figure 5.4-1 : Rapid charging of Hawker XT™ batteries.........................................................................44

Table 5.4-1 : Capacity returned as a function of inrush current .............................................................44

Table 5.4-2 : CV charging the Hawker XT™ battery at 14.7V.................................................................45

Table 5.5-1 : Recharge time and DOD ......................................................................................................45

Figure 5.6-1 : Temperature compensation of float voltage.......................................................................47

Figure 6.2-1 : Variation of cycle life with DOD ........................................................................................50



Figure 6.3-1 : Effect of temperature on float life .......................................................................................51

Table 6.4-1: Float life at temperatures and exposures .............................................................................53



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1.1 Introduction

he purpose of this manual is to describe the characteristics of the Hawker XT™ family

of valve regulated lead acid (VRLA) rechargeable batteries from Hawker Energy

Products Inc. and how best they may be used in different applications. The only com-

mon thread that unites these myriad applications is that they all have very harsh environmental

conditions.

The cost effectiveness, reliability, ruggedness and long life that have always been assets of

the lead acid battery have all been taken to new heights by the Hawker XT™ battery.

Currently five capacity sizes are available — 13Ah, 16Ah, 26Ah, 42Ah and 70Ah — all at the

10 hour rate of discharge. Except for the 13Ah size all Hawker XT™ batteries have Japan Industrial

Standard (JIS) footprint. Some key features of these batteries are described below.

1.2 Valve regulated design

he six cells within each Hawker XT™ battery are sealed to prevent electrolyte leakage.

Since the cell operates during its normal life without loss of water, even during con-

tinuous overcharge, no water or electrolyte checks are required. Because of its valve

regulated design, the battery can be oriented in any position for ease of installation. In addition, the

combination of a valve regulated design and a mechanically operated resealable Bunsen valve allows

the battery to be operated even in a vacuum.

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1.3 Wide operating temperature range

he exceptional low temperature performance of the Hawker XT™ battery has been

made possible by the use of plates that provide high surface area, coupled with a sepa-

rator system that maximizes diffusion and minimizes resistance effects. The overall

results are good utilization of active material and excellent voltage regulation over a wide tempera-

ture range.

By using an optional metal jacket the maximum operating temperature of the Hawker XT™

battery can be extended to 80°C (176°F). However, its life will appropriately affected.

1.4 High rate charge and discharge capabilities

he optimized electrochemistry of Hawker XT™ batteries contributes to high utilization

of the active plate materials and very low internal impedance. This means that they

can be discharged at high rates, allowing the use of smaller batteries for short dura-

tion, high rate discharges. Another advantage of the very low internal resistance is the fast recharge

capability of Hawker XT™ batteries.

1.5 Long life in float applications

he high purity of the lead–tin grid (the purity of lead is in excess of 99.99%) used in

Hawker XT™ batteries results in long life on float charge. These batteries have a de-

sign life expectancy of 10+ years at 25°C (77°C) under float conditions.

1.6 Advanced separator design

he Hawker XT™ battery incorporates an advanced material for its separators. This

material offers greater resistance to puncture, thereby making the battery virtually

free from internal plate-to-plate shorts. In addition the tougher separator imparts

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greater resistance to shock and vibration damage.

1.7 Ability to operate under intermittent charging

ecause of its very low rate of self discharge the electrical performance of a Hawker XT

battery is not compromised when charged intermittently. System designers can ex-

ploit the slow self discharge by periodically shutting off the chargers without harming

the battery.

1.8 Compliance with Bellcore and BS specifications

he Hawker XT design has been tested to and is compliant with Bellcore standard TR-

NWT-001210 and British Standards specification BS 6290 (iv).

1.9 Integral chimney and flash arrestor

very Hawker XT™ battery is equipped with an integral chimney built into the battery

cover, as shown in the illustration. The chimney can be used for external venting or for

underwater operation of the battery. In such a case a flexible pipe is attached to the chimney.

All batteries are also equipped with a

flash arrestor disk inside the chimney tower. The

flash arrestor prevents an external flame from

traveling back into the battery.

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Integral chimney



1.10 Superior internal packaging

typical failure mode in VRLA batteries is positive grid growth. The grid grows in all

directions, and unless vertical grid growth is constrained it can grow to a point where

it shorts the plate strap at the top of the cell. In the Hawker XT design, a mechanical

constraint is used to prevent the positive grid from growing upward and shorting out the strap.

1.11 Integral handles

he three larger Hawker XT batteries have lifting handles, allowing easier mechanical

handling. The 13Ah and 16Ah sizes do not have lifting handles because of their lighter

weights.

1.12 Flame retardant rating and lower oxygen index (LOI)

he case and cover material of all Hawker XT batteries is Noryl high temperature plas-

tic. They all have a V-0 flame retardant rating per Underwriters Laboratory (UL)

Standard 94. The LOI of the plastic is 39%.

The Noryl plastic used does not contain any polybrominated biphenyl ether (PBBE). PBBE’s

are the same as polybrominated biphenyloxides (PBBO’s), polybrominated diphenyl ethers

(PBDPE’s) and polybrominated diphenyloxides (PBDPO’s). The different names reflect different geo-

graphic terminology only. Noryl also does not contain tetrabromobisphenol-A (TBBA) or decabromo

biphenyl ethers.

Finally, the Noryl plastic used is in full compliance with the German Dioxin Ordinance.

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1.13 Transportation classification

ffective September 30, 1995, the Department of Transportation (DOT) has classified

all Hawker XT™ product as “nonspillable wet electric storage batteries.” Having

been tested and found in compliance with section 173.159 (d) of the 49 CFR, subchap-

ter 173.159, the Hawker XT™ product is exempt and unregulated regarding shipping requirements

of DOT 173.159. As a result, Hawker XT™ product does not have an assigned UN number,

nor does it require additional DOT hazard-communication labeling or placarding.

Hawker XT™ product may be shipped by air or ground transportation without restric-

tion.

Hawker XT™ batteries and their outside shipping containers must be labeled “nonspilla-

ble” or “nonspillable battery.” This labeling requirement is to clarify and distinguish to shippers

and transporters that all batteries have been tested and determined to be in compliance with DOT

HMR 49 Non-Hazardous Materials, and International Civil Aeronautics Organization (ICAO) and

International Air Transport (IATA) Packaging Instruction 806 and Special Provision A67 Vibration

and Pressure Differential Tests, and are therefore unregulated and classified as “nonspillable wet

electric storage battery.”

1.14 UL component recognition

ll Hawker XT™ batteries are recognized as components per UL 1989.

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2.1 Introduction

his chapter highlights some specific performance characteristics of the Hawker XT™

product line that make them a superior battery choice, particularly for demanding ap-

plications such as temperature extremes typically encountered in outdoor environ-

ments.

2.2 High discharge current

awker XT™ batteries can be discharged at very high currents while maintaining a

reasonably flat voltage profile. This characteristic is achieved because of the high

plate surface area and proximity of the plates to each other resulting from the use of

thin plates and high compression.

Detailed discharge characteristics of the full line of Hawker XT™ batteries to several end of

discharge voltages (EODV) are provided in a later chapter of the manual.

2.3 Low temperature operation

xceptional low temperature characteristics are maintained through the use of a sepa-

rator system that minimizes resistance to diffusion. This feature, combined with a

large plate surface area and high cell compression, results in efficient utilization of

active materials and excellent voltage regulation.

Because the battery operates as a "starved" electrolyte system, there is only enough electro-

lyte to maintain the rated capacity of the battery. The capacity available at low temperatures is a

function of both temperature and discharge current. Figure 2.3-1 illustrates the low temperature ca-

pability of Hawker XT™ batteries at three rates of discharge and down to −40°C.

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Figure 2.3-1 : Variation of capacity with temperature

2.4 Orientation flexibility

ith the starved electrolyte system, the sulfuric acid is absorbed within the cell plates

and the glass mat separator. The Hawker XT™ battery is virtually dry with no free

electrolyte, allowing it to be charged, discharged or stored in any position without

electrolyte leakage. However, upside down installation should be avoided in non-stationary applica-

tions because in this orientation the terminals would have to support the entire pack weight.

2.5 Recombinant VRLA design

ne of the most important features of the Hawker XT™ battery is its recombinant

valve regulated lead acid (VRLA) design. This mode of operation is possible be-

cause the cells within each battery is able to use the oxygen cycle during overcharge.

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The oxygen, evolved at the positive electrode when the cell is overcharged, is recombined at the

negative electrode. A self–resealing valve is provided as a safety vent in case of misapplication or

other abuse of the cell that would cause the internal cell pressure to increase.

In the Hawker XT™ product, water loss is greatly reduced due to two design features. First,

because water tends to decompose around impurities in the lead, the rate of such decomposition is

reduced due to the high purity of the lead used in these batteries.

In a conventional lead acid cell, the charge current electrolyzes the water to produce hydro-

gen from the negative electrode and oxygen from the positive electrode. Thus water is lost from the

cell, and it must be replenished by means of frequent topping up with water.

The evolution of the two gases does not occur at the same time due to the fact that the re-

charge efficiency of the positive electrode is less than that of the negative electrode. This means that

oxygen is evolved from the positive plate before the negative plate can generate hydrogen.

As oxygen is evolved from the positive plate, a significant quantity of highly active spongy

lead exists on the negative electrode before the negative plate can generate hydrogen. If the oxygen

that is generated by the positive plate can be transported to the negative plate, the spongy lead will

react rapidly with the oxygen to form lead oxide as shown by the following reaction:

2Pb + O2 →→→→ 2PbO (Eqn. 1)

The movement of oxygen from the positive electrode to the negative electrode is facilitated by

the use of highly porous separators that allow the oxygen to diffuse within the cell and cause the re-

action defined by Eqn. 1 above. The acidic conditions prevailing inside the cell is very conducive to

the reaction between lead oxide and the sulfuric acid to form lead sulfate in accordance with Eqn. 2

below:

2PbO + 2H2SO4 →→→→ 2PbSO4 + 2H2O (Eqn. 2)

As the lead sulfate is deposited on a surface that generates hydrogen, it (lead sulfate) is re-

duced to lead and sulfuric acid as indicated by Eqn. 3:



2PbSO4 + 2H2 →→→→ 2Pb + 2H2SO4 (Eqn. 3)

Adding the three equations and canceling out like terms on either side of the equations, we

obtain Eqn. 4:

2H2 + O2 →→→→ 2H2O (Eqn. 4)

The four equations given above illustrate the reactions that are the heart of the principle of

recombination that is employed by the Hawker XT™ product line. By properly designing the cell,

recombination efficiencies in excess of 99% are achieved in the Hawker XT™ battery.

2.6 Shock & vibration characteristics

he plate element in each cell is highly compressed, minimizing plate movement in high

shock or vibration applications. Movement in a vertical direction is also limited by the

mechanical constraint that prevents grid growth into the cell strap. In addition the

cast-on-strap that connects adjacent cells within the battery are buried in adhesive, providing fur-

ther protection against movement that could result when the battery is subjected to shock and vibra-

tion. Overall, the Hawker XT™ battery has excellent shock and vibration characteristics, as the fol-

lowing test results indicate.

2.6.1 MIL S-901C shock, high impact test

his is a test specified by the US Navy to determine suitability of equipment to be in-

stalled on warships. A 26Ah battery was installed in a UPS system aboard a Navy

MHC51 class coastal mine hunter.

The object of this test is to simulate the shock generated by a 16 in. naval gun and a depth

charge going off simultaneously. Testing is performed by hitting the UPS, while in operation, with a

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2,500 lb. hammer from varying distances. After several such impacts the battery system was success-

fully tested for proper functioning.

2.6.2 MIL S-167-1 for mechanical vibrations

n this test the batteries were subjected to three classes of vibration — exploratory vibra-

tion, variable frequency and endurance test.

Exploratory vibration test

The UPS unit containing the battery was vibrated from 5Hz to 33Hz at a table vibratory sin-

gle amplitude of 0.010 ± 0.002 in., in discrete frequency intervals of 1Hz. Vibration at each frequency

was maintained for 15 seconds.

Variable frequency test

The UPS unit was vibrated from 5Hz to 33Hz at 1Hz intervals at different amplitudes. At

each frequency the vibration was maintained for 5 minutes.

Endurance test

The test was conducted at 33Hz for two hours in the x- and y- axes at a table vibratory double

amplitude of 0.010 ± 0.002 in. The z-axis endurance test was conducted at 33Hz for two hours at a

table vibratory single amplitude of 0.020 ± 0.004 inch.

2.6.3 Vehicle vibration test

wo Hawker XT™ batteries were mounted in a special fixture and tested per the fol-

lowing parameters:

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Test direction Frequency Acceleration Duration

Vertical 10 – 12 Hz 3g 40 min.

Transverse 10 – 17 Hz 3g 40 min.

Horizontal 15 – 30 Hz 3g 40 min.

None of the four batteries showed noticeable failures at the end of the test.

2.6.4 Three axis vibration test

his test was conducted for Hawker Energy Products Inc. by an independent testing

facility. Two batteries were mounted in a special fixture and tested in the following

manner:

Test direction Frequency Acceleration Duration

33 3g 2 hr.

33 4g 2 hr.Vertical

33 6g 2 hr.

33 3g 2 hr.

33 4g 2 hr.Transverse

33 6g 2 hr.

33 3g 2 hr.

33 4g 2 hr.Horizontal

33 6g 2 hr.

Once again none of the four batteries showed any noticeable failures at the end of this test.

Summarizing, therefore, based on the tests described in this section there is little doubt

about the ability of the Hawker XT™ battery to withstand substantial levels of mechanical abuse.

2.7 Float life characteristics

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he life expectancy of Hawker XT™ products is not limited by loss of electrolyte. In-

stead, life expectancy is determined by long-term corrosion of the positive current col-

lecting grid. The corrosion effect on cell capacity is minimal until the cell approaches

end-of-life, which is defined as the inability of the cell to provide at least 80% of its rated capacity.

Stated in another way, the battery is considered to have reached its end-of-life when it has

lost 20% or more of its rated capacity. The Hawker XT™ product is designed to deliver 10+ years’ life

at 25°C (77°F) when used in a floating or standby application.

The float life of a pure lead VRLA battery is reduced by 50% for approximately every 8°C in-

crease in ambient temperature.

2.8 Float/cyclic capability

n many float applications, the battery may be called upon occasionally to cycle. In such

cases, it is important to have a battery that is capable of being cycled, even though the

charge voltage is set at the lower float value. The Hawker XT™ battery can rise to this challenge, as

demonstrated in Figure 2.8-1 below.

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5

10

15

20

25

0 0.2 0.4 0.6 0.8 1Recharge current in multiples of rated capacity

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Figure 2.8-1 : Hawker XT™ cycling at 13.62V at 25°C

The graph shows that, if the inrush current has a magnitude of 0.4C10 and a charge voltage

of 13.62V per battery, one can bring the battery back up to 100% state of charge (SOC) in only about

7½ hours. Even with as low an inrush as 0.2C10 the battery is back at 100% SOC in under 15 hours.

Thus the Hawker XT™ battery is more than capable of occasional cycling even though the charge

voltage is considerably less than the recommended values for cyclic applications.

It is critical to note here that even though Figure 2.8-1 suggests that the Hawker

XT™ VRLA battery may be cycled at 13.62V at 25°C, it would be a mistake to use this voltage

setting when the battery is expected to be cycled continuously or repeatedly. In such cases

the charge voltage must be raised to 14.7V to 15V per battery.

2.9 Cycle life characteristics

he life of a Hawker XT™ battery in a cyclic application is complex a function of the

depth of discharge (DOD), temperature and charging rate. Depending on the DOD,

the cycle life available can vary from 300 to more than 2,000. However, to obtain these

cycle numbers, the battery must be recharged effectively. More details may be found in Chapter 6.

2.10 Fast charging characteristics

fficient fast charging can be accomplished using a constant voltage charger with a

high initial current. With an initial charge current capability in the 2C101 range the

Hawker XT™ battery can be recharged to better than 95% state of charge in less than

one hour. Chapter 5 discusses the quick charging characteristics of the Hawker XT™ battery. Appli-

cations using fast charging must allow for periodic extended charging to maximize life.

1 The C10 rate of a battery is defined as the charge or discharge current in amperes that is numerically equal tothe rated capacity of a cell in ampere-hours at the 10 hr rate of discharge. Thus the 2C10 rate for a 13Ah cellwould be 26 amps.

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2.11 Storage characteristics

ll Hawker XT™ batteries may be stored for up to two years at room temperature

(25°C or 77°F) and recharged with no loss in battery reliability or performance capa-

bilities. The recharge may be accomplished without resorting to special charging tech-

niques.

When batteries are stored at or near 25°C we recommend conducting an open circuit voltage

(OCV) audit every six (6) months and recharging when OCV readings approach 12.00 volts per bat-

tery. Should storage temperatures be significantly higher than 25°C, even for short durations, the

frequency of OCV audits must be increased. Several storage-related graphs may be found in another

section of the manual.

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Ch. 3 : Discharging the Hawker XTCh. 3 : Discharging the Hawker XTCh. 3 : Discharging the Hawker XTCh. 3 : Discharging the Hawker XT™™™™ battery battery battery battery

3.1 Introduction

he standard discharge tables and curves for the Hawker XT™ family are shown at the

end of this chapter. The capacity available from a battery is a complex function of the

state of charge, temperature, the rate of discharge and the end of discharge voltage

(EODV). The graphs and tables provide the discharge performances of these cells to various EODVs.

3.2 Discharge voltage profile

igures 3.2–1(a) and 3.2–1(b) show room temperature (25°C) voltage profiles of Hawker

XT™ batteries when subjected to four loads — 0.1C10, 0.2C10, 1C10 and 2.2C10. In all

four cases, the low internal resistance of the battery allows very stable voltage pro-

files, regardless of whether the discharge rate is moderate (0.2C10 to 0.1C10) or at a high rate (1C10 to

2.2C10).

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0 1 2 3 4 5 6 7 8 9 10 11 12Time in hours at 25ºC

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Figure 3.2–1(a) : Medium rate discharge voltage profile

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" 1C 10 & 2.2C 10

Figure 3.2–1(b) : High rate discharge voltage profile



3.3 Discharge level

he voltage point at which 100% of the usable capacity has been depleted is a function

of the discharge rate. For optimum battery life, it is recommended that the battery be

disconnected from the load at this end voltage point. The recommended end of dis-

charge voltage (EODV) is a function of the rate of discharge, and these numbers are given in Table

3.3-1 below :

Table 3.3-1 : Recommended battery EODV

Discharge in amps EODV per battery

0.05C10 (C10/20) ≥≥≥≥ 10.50V

0.10C10 (C10/10) ≥≥≥≥ 10.20V

0.20C10 (C10/5) ≥≥≥≥ 10.02V

0.40C10 (C10/2.5) ≥≥≥≥ 9.90V

1.00C10 ≥≥≥≥ 9.60V

2.00C10 ≥≥≥≥ 9.30V

> 5.00C10 ≥≥≥≥ 9.00V

Allowing the Hawker XT™ battery to discharge under load to below these EODV levels or

leaving the battery connected to a load in a discharged state may impair the subsequent

ability of the battery to accept a charge

In "overdischarge" conditions, the sulfuric acid electrolyte can be depleted of the sulfate ion

and become essentially water, which can create several problems. A lack of sulfate ions as charge

conductors will cause the cell impedance to appear high and little charge current to flow. Longer

charge time or alteration of charge voltage may be required before normal charging may resume.

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Disconnecting the battery from the load will totally eliminate the possibility of an overdis-

charge, provided of course that it is put back on recharge immediately after the discharge. Doing so

will allow the battery to provide its full cycle life and charge capabilities.

It is important to note that when the load is removed from the battery, its terminal voltage

will increase — up to approximately 12V. Because of this phenomenon, some hysteresis must be de-

signed into the battery disconnect circuit so that the load is not continuously reapplied to the battery

as the battery voltage recovers.

3.4 Discharge characteristics

he graphs and tables that make up the rest of this chapter provide very detailed in-

formation on the discharge performance characteristics of all Hawker XT™ batteries.

The accompanying tables provide additional information on volumetric and gra-

vimetric power and energy densities. The reference temperature for all data presented is 25°C

(77°F).

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1

10

100

1000

5000

0.1

1

10

100

1000

5000

0.1 1 10 50

Hours per Hawker XT™ 13Ah battery to 1.75 VPC

" Watts # Amps

Figure 3.4-1 : Hawker XT™ 13Ah performance data to 10.5V (1.75 VPC)

Energy and power densitiesTime to10.5V

Watts(W)

Amps(A)

Capacity(Ah)

Energy(Wh) W/lit. Wh/lit. W/kg. Wh/kg.

2 min 1073 98.9 3.0 32 564.9 16.9 206.4 6.2

5 min 665 58.9 4.7 53 350.2 28.0 128.0 10.2

10 min 431 37.4 6.4 73 226.7 38.5 82.8 14.1

15 min 326 28.1 7.0 81 171.5 42.9 62.7 15.7

20 min 264 22.7 7.5 87 138.9 45.8 50.8 16.8

30 min 194 16.6 8.3 97 102.3 51.2 37.4 18.7

45 min 141 12.0 9.0 106 74.2 55.7 27.1 20.3

1 hr 112 9.5 9.5 112 58.7 58.7 21.5 21.5

2 hr 62 5.3 10.6 124 32.5 65.0 11.9 23.8

3 hr 44 3.7 11.1 131 23.1 69.2 8.4 25.3

4 hr 34 2.9 11.6 134 17.7 70.7 6.5 25.8

5 hr 28 2.4 12.0 138 14.5 72.6 5.3 26.5

8 hr 18 1.5 12.0 144 9.5 75.8 3.5 27.7

10 hr 15 1.2 12.0 150 7.9 78.9 2.9 28.8

20 hr 8 0.7 14.0 156 4.1 82.1 1.5 30.0



"""

""""""""""

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##

0.1

1

10

100

1000

5000

0.1

1

10

100

1000

5000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 1210 115.3 3.5 36 636.9 19.1 232.7 7.0

5 min 704 64.4 5.1 56 370.7 29.7 135.5 10.8

10 min 445 39.6 6.7 76 234.0 39.8 85.5 14.5

15 min 333 29.3 7.3 83 175.2 43.8 64.0 16.0

20 min 269 23.5 7.8 89 141.8 46.8 51.8 17.1

30 min 198 17.1 8.5 99 104.2 52.1 38.1 19.0

45 min 144 12.3 9.2 108 75.8 56.8 27.7 20.8

1 hr 114 9.7 9.7 114 60.0 60.0 21.9 21.9

2 hr 64 5.4 10.8 127 33.5 66.9 12.2 24.5

3 hr 45 3.8 11.4 135 23.7 71.0 8.7 26.0

4 hr 35 2.9 11.6 139 18.3 73.3 6.7 26.8

5 hr 29 2.4 12.0 144 15.2 75.8 5.5 27.7

8 hr 19 1.6 12.8 149 9.8 78.3 3.6 28.6

10 hr 16 1.3 13.0 156 8.2 82.1 3.0 30.0

20 hr 8 0.7 14.0 168 4.4 88.4 1.6 32.3



"""

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"""""""

"

###

##########

##

0.1

1

10

100

1000

5000

0.1

1

10

100

1000

5000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 1294 116.5 3.5 39 556.3 20.4 212.1 6.4

5 min 801 71.8 5.7 64 344.4 33.7 131.3 10.5

10 min 522 46.5 7.9 89 224.5 46.7 85.6 14.5

15 min 397 35.1 8.8 99 170.8 52.3 65.1 16.3

20 min 324 28.5 9.4 107 139.3 56.3 53.1 17.5

30 min 240 21.0 10.5 120 103.2 63.2 39.3 19.7

45 min 176 15.2 11.4 132 75.6 69.4 28.8 21.6

1 hr 140 12.0 12.0 140 60.1 73.6 22.9 22.9

2 hr 79 6.7 13.4 157 33.8 82.7 12.9 25.8

3 hr 55 4.7 14.1 166 23.7 87.2 9.0 27.1

4 hr 43 3.6 14.4 173 18.6 90.9 7.1 28.3

5 hr 35 2.9 14.5 177 15.2 93.1 5.8 29.0

8 hr 23 1.9 15.2 182 9.8 96.0 3.7 29.9

10 hr 19 1.6 15.6 186 8.0 97.9 3.0 30.5

20 hr 10 0.8 16.0 192 4.1 101.0 1.6 31.5



"""

""""""""""

""

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##

0.1

1

10

100

1000

5000

0.1

1

10

100

1000

5000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 1454 137.2 4.1 44 625.1 23.0 238.3 7.1

5 min 857 78.8 6.3 69 368.4 36.1 140.5 11.2

10 min 546 49.2 8.4 93 234.8 48.8 89.5 15.2

15 min 412 36.7 9.2 103 177.0 54.2 67.5 16.9

20 min 334 29.6 9.8 110 143.7 58.0 54.8 18.1

30 min 247 21.6 10.8 123 106.0 64.9 40.4 20.2

45 min 180 15.6 11.7 135 77.4 71.0 29.5 22.1

1 hr 143 12.3 12.3 143 61.7 75.5 23.5 23.5

2 hr 80 6.8 13.6 161 34.6 84.6 13.2 26.4

3 hr 57 4.8 14.4 171 24.5 90.0 9.3 28.0

4 hr 44 3.7 14.8 178 19.1 93.5 7.3 29.1

5 hr 36 3.0 15.0 180 15.5 94.7 5.9 29.5

8 hr 23 2.0 16.0 187 10.1 98.5 3.8 30.7

10 hr 19 1.6 16.0 192 8.3 101.0 3.1 31.5

20 hr 10 0.8 16.0 204 4.4 107.4 1.7 33.4



"""

""""

"""

""""

"

###

####

###

####

#

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 2181 203.4 6.8 73 591.0 19.7 196.5 6.6

5 min 1456 131.0 10.9 121 394.4 32.9 131.1 10.9

10 min 971 85.4 14.2 162 263.1 43.8 87.5 14.6

15 min 740 64.5 16.1 185 200.6 50.2 66.7 16.7

20 min 603 52.1 17.4 201 163.4 54.5 54.3 18.1

30 min 444 38.0 19.0 222 120.3 60.2 40.0 20.0

45 min 321 27.3 20.5 241 87.0 65.2 28.9 21.7

1 hr 253 21.4 21.4 253 68.6 68.6 22.8 22.8

2 hr 139 11.7 23.4 278 37.7 75.4 12.5 25.1

3 hr 97 8.1 24.3 290 26.2 78.5 8.7 26.1

4 hr 75 6.2 24.8 300 20.3 81.3 6.8 27.0

5 hr 61 5.1 25.5 306 16.6 82.9 5.5 27.6

8 hr 40 3.3 26.4 317 10.7 85.9 3.6 28.5

10 hr 32 2.7 27.0 324 8.8 87.8 2.9 29.2

20 hr 17 1.4 28.0 348 4.7 94.3 1.6 31.4



"""

""""

"""

""""

"

###

####

###

####

#

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 2459 236.0 7.9 82 666.5 22.2 221.6 7.4

5 min 1564 143.2 11.9 130 423.7 35.3 140.9 11.7

10 min 1018 90.6 15.1 170 275.8 46.0 91.7 15.3

15 min 769 67.5 16.9 192 208.3 52.1 69.2 17.3

20 min 622 54.2 18.1 207 168.6 56.2 56.1 18.7

30 min 455 39.2 19.6 228 123.4 61.7 41.0 20.5

45 min 328 28.0 21.0 246 88.9 66.7 29.6 22.2

1 hr 258 21.9 21.9 258 69.9 69.9 23.2 23.2

2 hr 142 11.9 23.8 283 38.4 76.7 12.8 25.5

3 hr 98 8.3 24.9 295 26.7 80.0 8.9 26.6

4 hr 76 6.4 25.6 305 20.7 82.6 6.9 27.5

5 hr 62 5.2 26.0 312 16.9 84.6 5.6 28.1

8 hr 40 3.4 27.2 322 10.9 87.2 3.6 29.0

10 hr 33 2.8 28.0 330 8.9 89.4 3.0 29.7

20 hr 17 1.5 30.0 348 4.7 94.3 1.6 31.4



"""

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""

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####

######

##

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 2941 274.2 9.1 98 526.8 17.6 180.4 6.0

5 min 1989 179.7 15.0 166 356.3 29.7 122.0 10.2

10 min 1348 119.2 19.9 225 241.4 40.2 82.7 13.8

15 min 1039 90.9 22.7 260 186.0 46.5 63.7 15.9

20 min 853 74.1 24.7 284 152.7 50.9 52.3 17.4

30 min 635 54.7 27.4 317 113.7 56.9 38.9 19.5

45 min 464 39.7 29.8 348 83.2 62.4 28.5 21.4

1 hr 368 31.3 31.3 368 66.0 66.0 22.6 22.6

2 hr 205 17.3 34.6 410 36.8 73.5 12.6 25.2

3 hr 144 12.0 36.0 432 25.8 77.4 8.8 26.5

4 hr 111 9.3 37.2 444 19.9 79.5 6.8 27.2

5 hr 91 7.6 38.0 456 16.3 81.7 5.6 28.0

8 hr 59 4.9 39.2 475 10.6 85.1 3.6 29.2

10 hr 48 4.0 40.0 480 8.6 86.0 2.9 29.5

20 hr 25 2.1 42.0 504 4.5 90.3 1.6 30.9



"""

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####

#

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 3347 322.3 10.7 112 600.0 20.0 205.4 6.9

5 min 2155 198.7 16.6 180 386.1 32.2 132.2 11.0

10 min 1423 127.7 21.3 237 254.9 42.5 87.3 14.6

15 min 1085 96.0 24.0 271 194.3 48.6 66.6 16.6

20 min 884 77.6 25.9 295 158.4 52.8 54.3 18.1

30 min 654 56.7 28.4 327 117.2 58.6 40.1 20.1

45 min 476 40.9 30.7 357 85.2 63.9 29.2 21.9

1 hr 376 32.1 32.1 376 67.4 67.4 23.1 23.1

2 hr 209 17.6 35.2 419 37.5 75.0 12.9 25.7

3 hr 146 12.3 36.9 439 26.2 78.7 9.0 26.9

4 hr 113 9.5 38.0 454 20.3 81.3 7.0 27.8

5 hr 92 7.7 38.5 462 16.6 82.8 5.7 28.3

8 hr 60 5.0 40.0 480 10.8 86.0 3.7 29.5

10 hr 49 4.1 41.0 492 8.8 88.1 3.0 30.2

20 hr 26 2.2 44.0 516 4.6 92.4 1.6 31.7



"""

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######

##

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 4786 448.0 13.4 144 503.7 15.1 169.7 5.1

5 min 3328 302.2 24.2 266 350.2 28.0 118.0 9.4

10 min 2275 202.3 34.4 387 239.4 40.7 80.7 13.7

15 min 1756 154.5 38.6 439 184.8 46.2 62.3 15.6

20 min 1440 125.8 41.5 475 151.6 50.0 51.1 16.9

30 min 1070 92.5 46.3 535 112.6 56.3 37.9 19.0

45 min 779 66.8 50.1 585 82.0 61.5 27.6 20.7

1 hr 617 52.6 52.6 617 64.9 64.9 21.9 21.9

2 hr 341 28.7 57.4 682 35.9 71.7 12.1 24.2

3 hr 238 19.9 59.7 713 25.0 75.0 8.4 25.3

4 hr 183 15.3 61.2 732 19.3 77.0 6.5 26.0

5 hr 149 12.4 62.0 747 15.7 78.6 5.3 26.5

8 hr 97 8.0 64.0 773 10.2 81.3 3.4 27.4

10 hr 79 6.5 65.0 786 8.3 82.7 2.8 27.9

20 hr 41 3.4 68.0 828 4.4 87.1 1.5 29.4



"""

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#

1

10

100

1000

10000

1

10

100

1000

10000

0.1 1 10 50


" Watts # Amps



Watts(W)

Amps(A)

Capacity(Ah)


2 min 5491 530.2 15.9 165 577.8 17.3 194.7 5.8

5 min 3648 338.2 27.1 292 383.9 30.7 129.4 10.3

10 min 2429 219.1 37.3 413 255.6 43.5 86.1 14.6

15 min 1852 164.7 41.2 463 194.9 48.7 65.7 16.4

20 min 1508 132.9 43.9 498 158.7 52.4 53.5 17.6

30 min 1109 96.6 48.3 555 116.8 58.4 39.3 19.7

45 min 803 69.2 51.9 602 84.5 63.4 28.5 21.4

1 hr 632 54.1 54.1 632 66.6 66.6 22.4 22.4

2 hr 347 29.3 58.6 694 36.5 73.0 12.3 24.6

3 hr 241 20.2 60.6 724 25.4 76.2 8.6 25.7

4 hr 186 15.5 62.0 744 19.6 78.3 6.6 26.4

5 hr 151 12.6 63.0 756 15.9 79.6 5.4 26.8

8 hr 98 8.2 65.6 787 10.4 82.8 3.5 27.9

10 hr 80 6.6 66.0 798 8.4 84.0 2.8 28.3

20 hr 43 3.5 70.0 852 4.5 89.7 1.5 30.2



Ch. 4 : Hawker XTCh. 4 : Hawker XTCh. 4 : Hawker XTCh. 4 : Hawker XT™™™™ battery s battery s battery s battery storagetoragetoragetorage

4.1 Introduction

nother area where the Hawker XT™ product has a significant advantage over conven-

tional VRLA batteries is storage. This chapter provides the reader with information

on using the long storage (shelf) life of these batteries to their advantage.

4.2 State of charge and open circuit voltage

he state of charge (SOC) of the Hawker XT™ battery can be approximated by first

measuring the open circuit voltage (OCV) and then using the curve given in Figure

4.2-1.

11.4

11.6

11.8

12

12.2

12.4

12.6

12.8

13

10 20 30 40 50 60 70 80 90 100State of charge, %

Figure 4.2-1 : Variation of OCV with state of charge

A

T



This curve is accurate to within 20% of the true SOC of the cell under consideration, if it has

not been charged or discharged within the past 24 hours. The curve is accurate to within 5% if the

cell has not seen any activity, charge or discharge, for the past 5 days.

4.3 Storage

atteries lose their stored energy when allowed to stand on open circuit due to the fact

that the active materials are in a thermodynamically unstable state. The rate of self–

discharge is dependent both on the chemistry of the system as well as on the tempera-

ture at which the battery is stored. The effect of temperature on capacity loss for Hawker XT™ bat-

teries in storage is illustrated in Figures 4.3-1(a) through 4.3-1(c).

60

65

70

75

80

85

90

95

100

0 10 20 30 40 50 60 70 80Weeks of storage at 25ºC

Figure 4.3-1(a) : Capacity degradation during storage at 25°C

B



20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20Weeks of storage at 45ºC

Figure 4.3-1(b) : Capacity degradation during storage at 45°C

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5 4Weeks of storage at 65ºC

Figure 4.3-1(c) : Capacity degradation during storage at 65°C



All Hawker XT™ products are capable of long storage without damage, as can be seen in the

above three graphs. At 25°C (77°F) the battery had more than 70% of its rated capacity after 64

weeks’ storage. As storage temperature increases the storage time reduces.

When Hawker XT™ batteries are kept in storage we recommend that the following two pro-

cedures be strictly followed:

1. The batteries must be fully charged before they are placed in storage

2. The OCV of each battery must be periodically monitored and the batteries recharged

when the OCV drops to 12.00V per module OR the battery has been in storage for two (2)

years, WHICHEVER OCCURS EARLIER

4.4 Overdischarge recovery characteristics

he ability of a battery to fully recover from an overdischarged state should be an im-

portant consideration. This is particularly true for outdoor installations where the bat-

tery can potentially stay in a discharged condition in extreme temperatures.

To demonstrate the capability of the Hawker XT™ battery to tolerate abusive storage condi-

tions, two separate tests were performed. The first is a test to verify that Hawker XT™ batteries can

meet or exceed the requirements of the appropriate German DIN standard while the second is an

even harsher test to determine the battery’s response to high temperature storage when it is in a dis-

charged state.

4.4.3 German DIN standard test for overdischarge recovery

n this test, a Hawker XT™ battery was discharged over 20 hours (0.05C10 rate) to

10.20V. After the discharge was complete, a 5Ω resistor was placed across the

battery terminals and the battery set aside for 28 days.

At the end of 28 days’ of storage, the battery was charged at 13.5V for only 48 hours. Another

0.05C10 discharge yielded 97% of rated capacity, indicating that a 48-hour charge after such as deep

T

I



discharge was not sufficient; however, the test is designed to show whether the battery can be recov-

ered from extremely deep discharges using only a standby float charger.

The results of this test conclusively prove that Hawker XT™ batteries can recover from very

abusive storage conditions. This conclusion is further reinforced by the following test which is even

harsher than the DIN standard test due to the fact that the battery was stored in a discharged state

at a temperature of 50°C or 122°F.

4.4.4 High temperature (50°/122°F) discharged storage test

n this test two battery samples were discharged at the 1-hour rate to 9V per module,

then set aside for storage at 50°C (122°F) in a discharged condition for four weeks.

At the end of four weeks the two batteries were recharged using a constant volt-

age (CV) charger at 14.7V per battery. As the graph below shows, both samples were able to recover

nicely from this extreme case of abusive storage.

As shown in Figure 4.4.4-1 the first two cycles were done using an inrush current of only

0.125C10. This inrush was clearly too low, as illustrated by the falling capacity on cycles 1 and 2.

However, as soon as the inrush current was raised to 1C10 the battery capacities bounced right back

up and had

I



"""""""

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"

#####

####

##

#####

#

#

80

85

90

95

100

105

110

0 2 4 6 8 10 12 14 16 18Cycle number

" Sample 1 # Sample 2

Current limit for cycles 1 & 2 : 0.125C10

Current limit for cycles 3 through 18 : C10

Figure 4.4.4-1 : Recovery of Hawker XT™ batteries from discharged storage at 50°C



Ch. 5 : Charging the Hawker XTCh. 5 : Charging the Hawker XTCh. 5 : Charging the Hawker XTCh. 5 : Charging the Hawker XT™™™™ ba ba ba battttteryteryterytery

5.1 Introduction

he superior charging characteristics of Hawker XT™ batteries make them the power

source of choice in demanding applications that require extremely rapid, or opportun-

istic, charging. Conventional sealed lead batteries are not suited for this type of

charging where charge currents can be of the order of 2C10 or higher.

5.2 General

harging Hawker XT™ batteries, like charging other rechargeable batteries, is a mat-

ter of replacing the energy depleted during the previous discharge. To complete the

charging process it is necessary to return more than 100% of the energy removed

during the discharge.

The Hawker XT™ battery incorporates the gas recombination principle, which allows up to

100% of the oxygen generated at up to the 0.33C10 overcharge rate to be recombined to form water at

the negative plate, eliminating oxygen outgassing. Hydrogen gas generation has been substantially

reduced by the use of pure lead–tin grid material, which has a high hydrogen overvoltage. The corro-

sion of the positive current collecting grid has been reduced by the use of pure lead–tin.

The amount of energy necessary for a complete recharge depends upon how deeply the cell

has been discharged, the method of recharge and power available, the recharge time and tempera-

ture. Typically, between 105% and 110% of the discharged ampere–hours must be returned for a full

recharge. Thus, for every ampere–hour discharged, one must put back between 1.05 and 1.10 am-

pere–hours to insure a full recharge.

If watt-hours rather than ampere–hours are measured, the required overcharge factor will be

higher. It is important to note that although the battery can deliver at or near its full capacity prior

T

C



to receiving the required overcharge, in order to obtain long cycle life, the battery MUST periodically

receive the required overcharge.

Charging can be accomplished by various methods. The objective is to drive current through

the cell in the direction opposite that of discharge. Constant voltage (CV) charging is the conven-

tional method for charging lead acid cells, and is recommended for Hawker XT™ batteries. However,

constant current (CC), taper current and variations thereof can also be used.

5.3 Constant voltage (CV) charging

onstant voltage (CV) charging is the most efficient method of charging Hawker XT™

VRLA batteries. The minimum inrush current for single level CV charging is of the

order of 0.4C10, and one must allow about sixteen (16) hours for a full charge from a

80% to 100% discharged state under repetitive cycling conditions. If the CV charger that is used has

an inrush current less than 0.4C10 then either the charge time allowed must be increased or special

charge algorithms must be evaluated.

Generally speaking, when the initial current is less than the 0.4C10 threshold, the charge

times must be lengthened by the hourly rate at which the charger is limited. In other words, if the

charger is limited to the 0.1C10 rate, then 10 hours should be added, giving a total charge time of 26

hours.

Note that there are no practical limitations on the maximum current imposed by the charg-

ing characteristics of the Hawker XT™ battery under constant voltage charge.

A very important note to keep in mind is that for cyclic applications, it is imperative that

the charge voltage be in the 14.7V to 15.0V per battery. Lowering the voltage to anything

under 14.7V in cyclic applications will lead to a rapid loss in capacity, regardless of the

magnitude of the inrush current.

C



5.4 Fast charging or cyclic charging

fast charge is broadly defined as a method of charge that will return the full capac-

ity of a cell in less than four hours. However, many applications require a return to a

high state of charge in one hour or less.

Unlike conventional parallel flat plate lead-acid cells, the Hawker XT™ battery uses a

starved electrolyte system where the majority of the electrolyte is contained within a highly retentive

fibrous separator, creating the starved environment necessary for homogeneous gas phase transfer.

The gassing problem inherent in flooded electrolyte sealed-lead batteries that utilized alloyed

lead is not evident with the Hawker XT™ system, as the extremely high purity of lead minimizes the

oxygen and hydrogen gas generation during overcharge and any oxygen gas generated is able to re-

combine within the sealed cell.

The high plate surface area of the thin plates used in these batteries reduces the current

density to a level far lower than normally seen in fast charge of conventional lead-acid cells, thereby

enhancing the fast charge capabilities.

The high charge efficiency of Hawker XT™ batteries allows them to be brought up to high

states of charge very quickly, making them a good choice where repeated discharges are likely, even

though the application may be of a standby nature. Figure 5.4-1 illustrates the fast charge charac-

teristics of the Hawker XT™ battery. Table 5.4-1 presents the same information in a tabular format.

A



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'

10

100

200

10 20 30 40 50 60 70 80 90 100Minutes on charge at 14.7V at 25ºC

" 0.8C 10

& 1.6C 10

' 3.1C 10

Figure 5.4-1 : Rapid charging of Hawker XT™ batteries

Table 5.4-1 : Capacity returned as a function of inrush current

Inrush current magnitudeCapacity

returned 0.8C10 1.6C10 3.1C10

60% 44 min. 20 min. 10 min.

80% 57 min. 28 min. 14 min.

100% 90 min. 50 min. 30 min.

Table 5.4-1 shows that using a constant voltage charge at 14.7V with an inrush current of

0.8C10 a 100% discharged battery can have 80% of its capacity returned in just 57 minutes; doubling

the inrush to 1.6C10 cuts the time taken to reach the same threshold capacity to only 28 minutes.

Table 5.4-2 provides a few additional data points defining the relationship between the

charge rate and percent of previous discharge capacity returned to the battery when it is charged at

CV of 14.7V per battery. In each case the battery was discharged to 100% DOD.



Table 5.4-2 : CV charging the Hawker XT™ battery at 14.7V

Charge timeCapacityreturned

1.5C10 inrush 2.5C10 inrush

50% 17 min. 12 min.

80% 27 min. 19 min.

90% 31 min. 24 min.

100% 60 min. 40 min.

Tables 5.4-1 and 5.4-2 and Figure 5.4-1 demonstrate very clearly the superior fast charge ca-

pabilities of the Hawker XT™ line of VRLA batteries.

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 2.5C10

compared with 60 minutes at 1.5C10 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.

5.5 Cycling Hawker XT™ batteries with lower inrush

lthough the Hawker XT™ battery does not require a current limit (initial current in-

rush) when being charged by a CV source, most practical applications have chargers

with limited power handling capabilities, thereby also restricting the current limit.

Recognizing this, cyclic charging tests were conducted using a CV charger that had only a

0.4C10 current limit. The charge voltage, however, was set at 14.7V. Table 5.5-1 shows the recom-

mended charge time as a function of the depth of discharge (DOD) of the battery.

Table 5.5-1 : Recharge time and DOD

A



DOD, % Charge time

Up to 30 5 hr.

31 to 50 8 hr.

51 to 100 16 hr.

5.6 Float charging and temperature compensation

hen Hawker XT™ batteries are to be used in a purely float or standby application at

an ambient temperature of 25°C (77°C), the recommended charge voltage range is

13.5 to 13.8V per battery. We also recommend that this charge voltage be tempera-

ture compensated.

High temperatures accelerate the rate of the reactions that reduce the life of a VRLA battery.

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 maximize life, a negative charging temperature coefficient is used at temperatures signifi-

cantly different from 25°C. Figure 5.6-1 plots the recommended float voltage per 12V module as the

ambient temperature varies. Note that the coefficient is negative — as the ambient tempera-

ture increases the charge voltage must be reduced, and vice versa.

W



12.9

13.4

13.9

14.4

14.9

15.4

15.9

16.4

-40 -30 -20 -10 0 10 20 30 40 50 60 70 80Ambient temperature, ºC

Figure 5.6-1 : Temperature compensation of float voltage

It is important to note here that even if the charge voltage is perfectly compensated for high

ambient temperatures, the float life expectancy of the battery would still be reduced. This is due to

the fact that while the charge currents are lowered because of lower charge voltages, the high ambi-

ent temperature continues to exert 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.

5.7 Constant current (CC) charging

onstant current (CC) charging is another acceptable method of charging a VRLA bat-

tery. CC charging of a battery is accomplished by the application of a nonvarying cur-

rent source. This charge method is especially effective when several batteries are

charged in series since it tends to eliminate any charge imbalance in a battery. CC charging charges

all cells or batteries equally because it is independent of the charging voltage of each cell in the bat-

tery.

C



However, this method of charging is NOT RECOMMENDED for float or standby applica-

tion because of its tendency to severely overcharge batteries that can remain on charge for

months or years at a time.

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Ch. 6 : Hawker XT™ battery service lifeCh. 6 : Hawker XT™ battery service lifeCh. 6 : Hawker XT™ battery service lifeCh. 6 : Hawker XT™ battery service life

6.1 Introduction

ll batteries have variable service life, depending upon the type of cycle, environment,

and charge to which the cell or battery is subjected during its life. Hawker XT™ prod-

ucts are no exception to this rule. There are two basic types of service life : cycle life

and calendar life.

6.2 Cycle life

cyclic application is basically an one where the discharge and charge times are of

about the same order. The cycle life of a battery is defined as the number of cycles a

battery delivers before its capacity falls below the acceptable level, usually defined as

80% of rated capacity.

Several factors influence the cycle life available from a battery. The depth of discharge (DOD)

is an important variable affecting the cycle life. For the Hawker XT™ series, the cycle life expectancy

is about 300 full DOD cycles. One can obtain more cycles with lower depths of discharge.

The quality of recharge is a critical determinant of the life of a battery in a given cyclic appli-

cation. In contrast to float applications where more than adequate time is allowed for a full recharge,

in cyclic applications a major concern is whether the batteries are being fully recharged in the time

available between discharges. If the recharge time is insufficient, the battery will "cycle down" or lose

capacity prematurely.

Figure 6.2-1 illustrates the dependence of the number of cycles obtained from a Hawker XT™

battery on the DOD of each cycle. The batteries were charged using a CV charger set at 14.7V per

battery.

A

A



100

1000

10000

50000

0 10 20 30 40 50 60 70 80 90 100Depth of discharge, %

Figure 6.2-1 : Variation of cycle life with DOD

In our experience, undercharging is a leading cause of premature capacity loss in cyclic ap-

plications. Although undercharge and overcharge are both detrimental to the life of a battery, the

time frame over which the effects of either undercharge or overcharge are felt is very different.

The impact of undercharging is felt much earlier than that of overcharge. Hence, for cyclic

applications, where the calendar life is relatively short, it is very important to ensure that the bat-

teries are not undercharged. For cyclic applications, it is preferable to err on the side of

overcharge than on the side of undercharge.

6.3 Float life

he design float life of the Hawker XT™ battery is ten plus (10+) years’ at room tem-

perature (25°C or 77°F) and under proper charging conditions. This design life has

been confirmed by the use of accelerated testing methods that are widely accepted by

both manufacturers and users of VRLA batteries. Figure 6.3-1 shows the variation in float life expec-

tancy as ambient temperature is varied.

T



0.1

1

10

20

0 10 20 30 40 50 60 70Ambient temperature, ºC

Figure 6.3-1 : Effect of temperature on float life

The primary failure mode of Hawker XT™ batteries can be defined as positive current col-

lecting grid corrosion and growth. Because this corrosion and growth are the result of chemical reac-

tions within the cell, the rate of corrosion and growth increases with increasing temperature as ex-

pressed by the widely-accepted Arrhenius equation.

6.4 Float life estimation based on actual temperatures

he float life expectancy of a VRLA battery should not be based on an average ambient

temperature. This can be illustrated by considering the following simple example.

Suppose the battery spends six months of every year at 15°C and the balance six months at 35°C.

The average temperature is 25°C, so on the basis of the average temperature one can expect the full

12+ years’ design life. This clearly overestimates the actual life expectancy, as illustrated below.

Since battery life is reduced by 50% for every 8°C increase in temperature, raising the tem-

perature from 25°C to 35°C accelerates battery aging by a factor of 21.25 or 2.378. In other words,

T



every day spent by the battery at 35°C is equivalent to the battery spending 2.378 days at 25°C. So a

battery that sits at 35°C for 6 months has spent the equivalent of 14.268 months.

Therefore, by sitting for six months at 25°C and for six months at 35°C, the battery has used

up the equivalent of 20.268 months (6 months + 14.268 months) or 1.689 years at 25°C. Although it

has spent one calendar year in service, in terms of its life at 25°C it has seen 1.689 years’ service.

Thus the actual life expectancy of the Hawker XT™ battery under these conditions will be 12+/1.689

years or about 7.1+ years.

This simplified example illustrates the importance of using actual temperatures and times of

exposure to estimate float life expectancy in specific applications

Table 6.4-1 below shows float expectancy when the Hawker XT™ battery has been exposed

for various time periods to a range of temperatures. For example if the battery were to be exposed to

35°C (95°F) for three months out of every year, the expected float life of the Hawker XT™ battery

will be 8.9+ years instead of its design life of 12+ years at 25°C (77°F).

If Ldesign is the float life at 25°C and M is the number of months per year the battery is ex-

posed to T°C the acceleration factor AF and actual life expectancy Lactual may be calculated in a two-

step fashion as below. Table 6.4-1 entries have been computed in this manner.

Step 1 : Determine acceleration factor, AF

( ) [ ]12

M12M8/25T2AF

−+

−

=

Step 2 : Calculate actual life expectancy

AF

LL design

actual =



Table 6.4-1: Float life at temperatures and exposures

Battery ambient under temperature compensated float chargeMonthsper yr.

25°C 30°C 35°C 40°C 45°C 50°C 55°C

1 12+ 11.5+ 10.8+ 9.8+ 8.7+ 7.3+ 5.9+

2 12+ 11.0+ 7.8+ 8.3+ 6.8+ 5.3+ 3.9+

3 12+ 10.6+ 8.9+ 7.2+ 5.5+ 4.1+ 2.9+

4 12+ 10.2+ 8.2+ 6.4+ 4.7+ 3.4+ 2.3+

5 12+ 9.8+ 7.6+ 5.7+ 4.1+ 2.8+ 1.9+

6 12+ 9.4+ 7.1+ 5.1+ 3.6+ 2.5+ 1.7+

7 12+ 9.1+ 6.7+ 4.7+ 3.2+ 2.2+ 1.5+

8 12+ 8.8+ 6.3+ 4.3+ 2.9+ 2.0+ 1.3+

9 12+ 8.5+ 5.9+ 4.0+ 2.7+ 1.8+ 1.2+

10 12+ 8.3+ 5.6+ 3.7+ 2.5+ 1.6+ 1.1+

11 12+ 8.0+ 5.3+ 3.5+ 2.3+ 1.5+ 1.0+

12 12+ 7.8+ 5.1+ 3.3+ 2.1+ 1.4+ 0.9+

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Ch. 7 : Safety issuesCh. 7 : Safety issuesCh. 7 : Safety issuesCh. 7 : Safety issues

7.1 Introduction



here are two main considerations relative to the application of Hawker XT™ batteries

that should be recognized to assure that the usage is safe and proper. These are gas-

sing and shorting.

7.2 Gassing

ead-acid batteries produce hydrogen and oxygen gases internally during charging and

overcharging. The gases released or diffused must not be allowed to accumulate. An

explosion could occur if a spark were introduced.

During normal charging operation, some hydrogen gas is released (vented) or diffused

through the container walls. The pure lead–tin grid construction as well as the extremely high purity

of lead oxides and sulfuric acid used in the manufacture of Hawker XT™ batteries all serve to mini-

mize the amount of hydrogen gas produced.

The minute quantities of gases that are released or diffused from the battery with recom-

mended rates of charge and overcharge will normally dissipate rapidly into the atmosphere. Hydro-

gen gas is difficult to contain in anything but a metal or glass enclosure. It can permeate a plastic

container at a relatively rapid rate.

Because of the characteristics of gases and the relative difficulty in containing them, most

applications will allow for their release into the atmosphere. If any Hawker XT™ products are being

designed into a gas-tight container, precautions must be taken so that the gases produced during

charge can be released into the atmosphere.

If hydrogen is allowed to accumulate and mix with the atmosphere at a concentration rang-

ing from 4% to 96% by volume, an explosive mixture is formed that would be ignited in the presence

of a flame or spark.

Another consideration is the potential failure of the charger. If the charger malfunctions,

causing higher-than-recommended charge rates, substantial volumes of hydrogen and oxygen will be

vented from the cell. This mixture is explosive and should not be allowed to accumulate. Therefore,

despite its significant advantages over other lead-acid batteries, Hawker XT™ batteries MUST

NEVER BE CHARGED IN A GAS-TIGHT CONTAINER.

T

L



7.3 Shorting

ll Hawker XT™ batteries have very low internal impedance and thus are capable of

delivering high currents if externally short circuited. The resultant heat can cause

severe burns and is a potential fire hazard. Personnel working near the open termi-

nals of cells or batteries are strongly advised to avoid wearing metal rings or watchbands.

Inadvertently placing these metal articles across the terminals could result in se-

vere skin burns. It is a good practice to remove all metallic items such as watches, bracelets

and personal jewelry when working on or around battery terminals.

As a further precaution, when installing batteries or working on them, insulating gloves

should be worn and only insulated tools should be used to prevent accidental short circuits.

!!!!!!!!!!!!!!!

A

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