Post on 17-Feb-2018
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Stationary Battery SizingStationary Battery Sizing
Presented by:
Lesley Varga, P.E.
Quality Standby Services, LLC1649 Sands Place, SE, Suite C
Marietta, GA 30067
(770) 916-1747
lesley@qualitystandbyservices.com
www.qualitystandbyservices.com
IEEE IAS Atlanta Chapter
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Safety First!
Basic PPE
Safety First!
Basic PPE
Personal Protective Equipment –example:
– Goggles and face shields, eye protection
– Acid-resistance gloves
– Protective aprons
– Emergency eye-wash and safety showers
– Bicarbonate soda and water for neutralization
(mixed to the ratio of 1 lb. to 1 gallon)
– Insulated tools
– Class C fire extinguisher
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Personal Protective EquipmentPersonal Protective Equipment
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WARNING !!! WARNING !!!GAS PRODUCED BY THIS BATTERY CAN BE
EXPLOSIVE. PROTECT EYES WHEN AROUND
BATTERY. PROVIDE ADEQUATE VENTILATION
SO HYDROGEN GAS ACCUMULATION IN THE
BATTERY AREA DOES NOT EXCEED ONE
PERCENT BY VOLUME. DO NOT SMOKE, USEOPEN FLAME OR CREATE SPARKS NEAR THE
BATTERY.
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WARNING !!! WARNING !!!
THE BATTERY CONTAINS SULFURIC ACID
WHICH CAN CAUSE SEVERE BURNS. IN
CASE OF SKIN CONTACT WITH
ELECTROLYTE, REMOVE CONTAMINATEDCLOTHING AND FLUSH AFFECTED AREAS
THOROUGHLY WITH WATER. IF EYE
CONTACT HAS OCCURRED, FLUSH FOR A
MINIMUM OF 15 MINUTES WITH LARGEAMOUNTS OF RUNNING WATER AND SEEK
IMMEDIATE MEDICAL ATTENTION.
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WARNING !!! WARNING !!!
SHOCK HAZARD – DO NOT TOUCHUNINSULATED BATTERY
CONNECTORS OR TERMINALS. BE
SURE TO DISCHARGE STATIC
ELECTRICITY FROM TOOLS AND
TECHNICIAN BY TOUCHING A
GROUNDED SURFACE IN THE
VICINITY OF THE BATTERIES BUTAWAY FROM THE CELLS AND FLAME
ARRESTERS.
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Lamps
Relays
Breaker
Coils
Switchgear and Control DC systemSwitchgear and Control DC system
AC→DC
24, 48,125 or
240 VDC
VAC
1Φ or 3Φ
Charger/Rectifier + -
Battery
Switchgear
Controls
Motors
Pumps
Valves
DC Loads
“125VDC” Bus: 133.8 VDCTypical Float Voltage
Inverter
DC→AC
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Lamps
Relays
Breaker
Coils
System One Line - AC Input LostSystem One Line - AC Input Lost
AC→DC
24, 48,125 or
240 VDC
VAC
1Φ or 3Φ
Charger/Rectifier
+ -
Battery
Switchgear
Controls
Motors
Pumps
Valves
DC Loads
Inverter
DC→AC
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Utility
AC
Input
Transfer Sw
Generator
AC→DC
Rect. #1
AC→DC
Rect. #n
AC→DC
Rect. #n+1
Battery
Bus Work
Power
Board
Distribution
to Loads
+ -
Telecom DC System“48 VDC” Bus: 54.2 VDC
Typical Float Voltage
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Utility
AC
Input
Transfer Sw
Generator
AC→DC
Rect. #1
AC→DC
Rect. #n
AC→DC
Rect. #n+1
Battery
Bus Work
Power
Board
Distribution
to Loads
+ -
Telecom DC System -AC Input Lost“48 VDC”: 54.2 VDC
Typical Float Voltage
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Utility
AC
Input
Transfer Sw
Generator
AC→DC
Rect. #1
AC→DC
Rect. #n
AC→DC
Rect. #n+1
Battery
Bus Work
Power
Board
Distribution
to Loads
+ -
Telecom DC System – AC Lost,
Generator On Line
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Utility AC Input
Transfer Switch
Generator
Rectifier
AC→DC
Inverter
DC→AC
UPS
+ -
Battery
Typical UPS System
Loads
“480 VDC Bus”: 540 VDC Float
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Utility AC Input
Transfer Switch
Generator
Rectifier
AC→DC
Inverter
DC→AC
UPS
+ -
Battery
UPS System –Utility Lost
Before Generator
Loads
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Utility AC
GeneratorUPS Battery480 Volt 240
cells
LOADS
UPS
Switchgear
Switchgear Battery
125 V/48 V
Engine
Starting Battery24 volt
Inverter Rectifier
Telecom
Equip
48 VDC
Telecom Battery
48 V /24 cells
Batteries in Mission Critical Applications
Emergency
Lighting
Emergency
Lighting
Battery
TransferSwitch
Fire Pump Fire PumpBatteries
Substation Battery
125 volt
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Definition of a CellDefinition of a Cell
Cell: A unit part consisting of twodissimilar electrodes immersed in an
electrolyte;
One lead acid cell is 2 volts nominal
One nickel cadmium cell is 1.2 volts
nominal
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String: An energy storage system
consisting of two or more seriesconnected cells up to the required
system voltage
Definition of a String
Lead Acid
“125 Vdc” = 58-60 cells
Typical Float = 130-134Vdc
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Nickel Cadmium
“125 Vdc” = 90-96 cells
Typical Float =130 -134 Vdc
Definition of a String
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Battery BasicsBattery Basics
Separators
2 Volts
Positive
Plate
Negative
Plate
Within the cell the plates are connected in parallel.
If each positive plate is 100 Amp Hours in capacity, the cell is 300 Amp Hour .
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Battery BasicsBattery Basics
Series connection of Cells
– Start with Cell # 1 Positive,connecting from a negativeterminal on cell #1 to a positiveterminal on adjacent cell (typicalconnection within a battery
string) – Add up the cell voltage, but the
Amp-hour stays the same
– Example: Two 6V-25Ahr unitsconnected in series = 12 Volt,25 Amp-hour
Cell #1………. Cell # n
+ - + - + - + -
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Battery BasicsBattery Basics
Parallel connection
– Connecting from a positiveterminal on one battery to apositive terminal on anotherbattery
– Sum the Capacity of each string(Watts or Amp Hours); the voltageremains the same
– Example: Two 6V-25 Amp hourunits connected in parallel =
System: 6 Volts, 50 Amp-hours
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Lead Acid Battery Lead Acid Battery
Lead dioxide Positive plate,PbO2
Metallic sponge lead Negative
plate, Pb Immersed into an electrolyte of
Water & Sulfuric Acid, H2SO4
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Types of Lead Acid Battery Types of Lead Acid Battery
Vented Lead Acid (“VLA”) – Also called Flooded or Wet
– Lead-Calcium (most common), Lead- Antimony, Low Antimony (“lead selenium”and Pure Lead
Valve Regulated Lead Acid (“VRLA”) – Also called Sealed (not maintenance free)
– Lead Calcium
– Pure Lead – AGM design(Absorbed Glass Mat)
– Gel design
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Post
Strap
Plate
Vent
Cover
Container
Lead Acid Cell ComponentsLead Acid Cell Components
Separator
2 Volt VRLAVLA (Flooded)
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Lead Acid Grids and PlatesLead Acid Grids and Plates
Negative PlateGrid
Positive
Plate
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26
Separator: prevents electrical contact between the positive and
negative plates while maintaining sufficient electrolyte to sustain
capacity
Flooded: micro porous separator
– Grooved design to allow free
liquid and gas movement within cell
– Provides prevention from shorts
– Glass mat may be used
VRLA: “absorbent glass mat” wraps
positive and negative plates
– AGM
– Gel
SEPARATORSSEPARATORS
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Telecom Battery
Low Rate/LongDuration
UPS Battery
High Rate/ShortDuration
Switchgear Battery
General PurposeStep Loads
Nominal 8 hr discharge
rate
Nominal 15 min.
discharge rate
Combination of long &
short duration rates
Thicker pos plates Thinner pos plates Moderately thick plates
Plates farther apart Plates very close Moderate plate center
High electrolyte to
plate ratio
Low electrolyte to
plate ratio
Moderate electrolyte to
plate ratioMinimal cycling Improved cycling Moderate cycling
Poor high rates Very good high rates Reliable high rates
Good long rates Poor long rates Reliable long rates
Lead Acid Battery Design DifferencesLead Acid Battery Design Differences
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Nickel Cadmium Battery Nickel Cadmium Battery
Nickel positive plate
Cadmium negative plate
Immersed into an electrolyte of
Potassium Hydroxide (alkaline)
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Nickel Cadmium Design DifferencesNickel Cadmium Design Differences
LLow rate ofdischarge
MMediumrate of
discharge
HHigh rate ofdischarge
Cell type L M H
Railway X X X
Emergency lightning X
Telecommunication X X
Industrial X X X
Photovoltaic X
Diesel start X
UPS X X X
Utility Equipment X X X
Emergency supply X X X
Alarm equipment X
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Nickel Cadmium - Internal Construction Nickel Cadmium - Internal ConstructionL
Low Rate of
Discharge
MMedium Rate of
Discharge
H
High Rate of
Discharge
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IEEE Standards, Guides, PracticesIEEE Standards, Guides, Practices IEEE Std 485 -2010: Sizing, Stationary Lead Acid
IEEE Std 1184-2006: Batteries for UPS Systems
IEEE Std 1189 -2007: Selection & Sizing VRLA
IEEE Std 1115-2014: Sizing Nickel Cadmium
Additional System Considerations:1375 – Protection of Battery Systems
1578 – Spill Containment
1491 – Monitoring Systems
1635 – Guide to Ventilation design
1657 –Personnel Qualifications for Install & Maint
946 – Design of DC Auxiliary Power Systems for
Generating Stations (charger sizing)
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General Sizing ConsiderationsGeneral Sizing Considerations
The battery must supply the DC power
when:
1. The load on the dc system exceeds themaximum output of the charger
2. The output of the charger is interrupted
3. The AC power is lost (may result ingreater dc power demand than item 2.)
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Define the System LoadsDefine the System Loads
Continuous – energized throughout the duty
cycle
Noncontinuous - energized only during a
portion of the duty cycle, defined durationMomentary - short duration loads not
exceeding 1 minute at any occurrence.
– Lead Acid: considered a full minute,1 minute – Nickel Cadmium: for loads < 1 sec, consider
1 second
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Define Load & ApplicationDefine Load & Application
Steady Loads – typically Telecom,
“long duration” 8 hour backups
KVA/KW Loads – typically UPS, “high
rate, short duration” 15 minutes,KVA/KW ratings
Step Loads –Switchgear & Control –
Utility Applications – “step loads” -combination of high rates and long
duration
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Load ClassificationLoad ClassificationThe loads applied to the battery are
either: – Constant power (inverters, dc/dc power
supplies)
– Constant resistance (dc motor starting,
relays, contactors, lights)
– Constant current (running dc motors)
For Sizing purposes, loads are treated
as Constant Power or Constant Current
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Selection Factors to be ConsideredSelection Factors to be ConsideredPhysical characteristics of the cells
Planned life of the installationFrequency and depth of discharge
Charging characteristics
Maintenance requirements
Cell orientation requirements
Ventilation requirementsSeismic characteristics
Spill management
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Battery Size – Nominal Rating Battery Size – Nominal Rating
Ampere-hour : 8 hour capacity of a lead
acid storage battery (in the US) – The quantity of electricity that the battery
can deliver in amp-hours at the 8 hour rate.
– Example: a “2000 Ampere Hour” batterywill provide 250 amps for 8 hours to 1.75volts per cell
(2000/8 = 250 amps continuously for 8hours)
Nickel Cadmium: 5 hour or 10 hour or 20hour rate
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Battery Size – Constant PowerRating
Battery Size – Constant PowerRating
UPS batteries are rated in Watts or kW
– kW/cell x number of cells = kWb
For a specified time period to a specified endvoltage, e.g.15 minutes to 1.67 volts per cell
Battery is typically sized for full load of theUPS system
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Important Sizing ConsiderationsImportant Sizing Considerations
Operating Temperature
– Affects the available capacity
– Size for the lowest expected
temperature
– At high temperatures use the ratedcapacity for 77° F
– High temperature affects battery life
– Cold temperature affects battery
capacity
– For Nickel Cadmium- see manufacturer
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Temperature Correction Factors Temperature Correction FactorsFrom IEEE Std 485-2010
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Important Sizing ConsiderationsImportant Sizing Considerations
Aging Margin – LEAD ACID: – Replacement criteria = 80% of rated
capacity.
– Battery is defined at end of life at 80%capacity
– The initial rated capacity of the
battery should be at least 125 percent(1.25 aging factor) of the loadexpected at the end of its service life.
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Important Sizing ConsiderationsImportant Sizing Considerations Aging – NICKEL CADMIUM:
– No defined end of life point
– Capacity gradually decreases (linear)
– 1.25 margin is typically used
– Aging margins of 1.10 – 1.40 may apply
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Important Sizing ConsiderationsImportant Sizing Considerations
Initial Capacity
– Batteries may have less than rated
capacity when delivered. Unless 100 %
capacity upon delivery is specified, theinitial capacity can be as low as 90% of
rated capacity (per IEEE-485)
– Typical UPS and Switchgear batteriesship at 100%; Telecom at 90%
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Important Sizing ConsiderationsImportant Sizing Considerations
Nickel Cadmium
– For the float application (telecom,
switchgear, UPS), make sure to usethe data based on Constant Potential
Float Charging.
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Important Sizing ConsiderationsImportant Sizing Considerations
Design margin
– It is prudent to provide a capacity
margin to the battery sizing for
unforeseen additions to the dc systemand less than optimum operating
conditions.
– Typical design margins are 10-15%.
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Battery SizeBattery Size Factors governing battery size:
– Maximum system voltage – Minimum system voltage
– Correction factors (e.g. aging, temperature)
– Duty cycle
If cells of sufficiently large capacity are notavailable, then two or more strings may be
connected in parallel. The capacity of such abattery is the sum of the capacities of thestrings.
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Number of CellsNumber of Cells
The maximum and minimum allowablesystem voltage (“voltage window”)determines the number of cells in thebattery.
When the battery voltage is not allowedto exceed a given maximum system
voltage the number of cells will belimited by the cell voltage required forsatisfactory charging.
M i V ltM i V lt
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Maximum Voltage
48 Volt Telecom Example
Maximum Voltage
48 Volt Telecom ExampleNumber of cells =
Maximum system voltageMax cell voltage required for charging
Given: 2.33 volts per cell required for equalize chargingMaximum allowable system voltage = 56 V and 54 V
56 V = 24 cells
2.33 Vpc
54 V = 23 cells
2.33 Vpc
Minimum VoltageMinimum Voltage
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Minimum Voltage
Telecom Example
Minimum Voltage
Telecom ExampleMinimum battery voltage equals the
minimum system voltage plus the cable
voltage dropMinimum system voltage at the equipment: 42 VDC
Allowable voltage drop from battery to load: 2 VDC
Minimum battery voltage: (42 + 2) = 44 VDC
Minimum battery voltage = minimum cell voltage
Number of cells
Given: the minimum allowable battery voltage is 44 Volts
and the maximum number of cells is 24 or 23:44V = 1.83 volts per cell
24 cells
44V = 1.91 volts per cell
23 cells
Maximum VoltageMaximum Voltage
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Maximum Voltage
Switchgear Example
Maximum Voltage
Switchgear ExampleNumber of cells =
Maximum system voltagecell voltage required for charging
Given: 2.33 volts per cell required for equalize chargingMaximum allowable system voltage either 140 V or 135 V
140 V = 60.08 cells: use 60 cells
2.33 Vpc
135V = 57.94 cells: use 58 cells
2.33 Vpc
Minimum VoltageMinimum Voltage
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Minimum Voltage
Switchgear Example
Minimum Voltage
Switchgear ExampleMinimum battery voltage equals the
minimum system voltage plus the cable
voltage dropMinimum system voltage at the equipment: 103 VDC
Allowable voltage drop from battery to load: 2 VDC
Minimum battery voltage: (103 + 2) = 105 VDC
Minimum battery voltage = minimum cell voltage
Number of cells
Given: the minimum allowable battery voltage is 105 Volts
and the maximum number of cells is 60 or 58:105V = 1.75 volts per cell
60 cells
105V = 1.81 volts per cell58 cells
Maximum VoltageMaximum Voltage
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Maximum Voltage
UPS Example
Maximum Voltage
UPS ExampleNumber of cells =
Maximum system voltagecell voltage required for charging
Given: 2.38 volts per cell (1.250 sp. gr.) and 2.33 vpc (1.215sp.gr.) required for equalize charging
Maximum allowable system voltage: 576 VDC
576 V = 240 cells2.38 Vpc
576 V = 247 cells: (typical 240-244 cells)
2.33 Vpc
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Minimum Voltage UPS ExampleMinimum Voltage UPS ExampleMinimum battery voltage equals the
minimum system voltage plus the cable
voltage dropMinimum system voltage at the UPS equipment: 396 VDC
Allowable voltage drop from battery to UPS: 4 VDC
Minimum battery voltage: (396 + 4) = 400 VDC
Minimum battery voltage = minimum cell voltage
Number of cells
Given: the minimum allowable battery voltage is 400 Voltsand the maximum number of cells is 244
400V = 1.67 volts per cell
240 cells
400V = 1.64 volts per cell
244 cells
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Sizing Example: TelecomSizing Example: Telecom
Constant Current loads
Sizing for:
– Load = 400 Amps for 8 hours
– 24 cells, battery end voltage 1.75 vpc
– Aging margin: 1.25
– Design margin: 1.10
– Temperature factor at 77°F: 1.00
= 400 x 1.25 x 1.10 x 1.0 = 550 Amps continuously
for 8 hours to 1.75 vpc:
4,400 Ampere hour battery
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Sizing Example: UPS Battery Sizing Example: UPS Battery UPS Specifications require a 300 kW Battery (kWb) for 15
minutes, 240 cells, 400 Vdc end voltage (1.67 vpc):
– The lowest ambient temperature: 65°F
– Battery must be sized for 300 kW at end of life
– 300 kWb x 1.080 (temp correction) x 1.25 (aging
margin for 300 kW at end of life)
= 300 x 1.080 x 1.25 x = 405 kWb
– Select a battery that will provide 405 kW
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1.250 Specific Gravity
Discharge Rates in kW per Cell to 1.67Vpc at 25°C (77°F)
1.250 Specific Gravity
Discharge Rates in kW per Cell to 1.67Vpc at 25°C (77°F) Type TIME
5 10 11 12 13 14 15 16 17 18 19 20
DXC-5B 0.908 0.758 0.735 0.713 0.693 0.673 0.653 0.634 0.616 0.599 0.582 0.567
DXC-7B 1.350 1.124 1.091 1.059 1.029 1.000 0.971 0.943 0.917 0.891 0.866 0.843
DXC-9B 1.785 1.483 1.437 1.395 1.355 1.317 1.280 1.245 1.212 1.179 1.148 1.117
DXC-11B 2.154 1.891 1.832 1.774 1.718 1.663 1.610 1.560 1.512 1.467 1.425 1.385
DXC-13B 2.585 2.239 2.166 2.096 2.028 1.964 1.903 1.845 1.791 1.740 1.691 1.645
DXC-15B 3.016 2.580 2.493 2.410 2.331 2.256 2.185 2.120 2.057 1.999 1.944 1.893
DXC-17B 3.447 2.908 2.808 2.712 2.622 2.538 2.459 2.387 2.319 2.255 2.195 2.139 1.900 1.707
Example: UPS System requires a 405 kWb (300kWb EOL),240 cells for 15 minutes to 400 VDC (400/240cells = 1.67
volts per cell); 405/240 cells = 1.688 kW/cell
Select the DXC-13B at 1.903 kW/c x 240 cells = 456 kWb
When Battery kW (“kWb”) is UnknownWhen Battery kW (“kWb”) is Unknown
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When Battery kW ( kWb ) is Unknown
But UPS kVA is Known
When Battery kW ( kWb ) is Unknown
But UPS kVA is Known
Battery kWb = kVA x p.f efficiency of inverter
kVA = kVA is the Inverter output or load
p.f. = the power factor
Efficiency = the efficiency of the inverter
Battery kW = kW/cell X 1.25 for EOL Sizing# of Cells
Sizing Example: Switchgear &Sizing Example: Switchgear &
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Sizing Example: Switchgear &
Control / Utility
Sizing Example: Switchgear &
Control / Utility
Duty Cycle
– Combination of continuous, noncontinuous
and momentary loads – All loads expressed in constant Current or
constant Power
– Time span of the duty cycle is determined bythe requirements/design
Sizing Example: Switchgear &Sizing Example: Switchgear &
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g p w g
Control
g p w g
Control
Sizing Example: Switchgear &Sizing Example: Switchgear &
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g p g
Control
g p g
Control
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Example: Substation Battery DutyExample: Substation Battery Duty
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p y y
Cycle
p y y
Cycle
100
AMPS
45
2
min 1 239
Hours 1 2 3 4
Time
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EnerSys Battery Sizing Program“BSP”EnerSys Battery Sizing Program“BSP”
Register on-line at:
http://www.enersysreservepower.com/
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Engineer, Furnish and InstallEngineer, Furnish and Install
Standby Power Products for the Utility,
UPS and Telecom Applications Application and System Design
– Registered Electrical PE
– Technicians with Electrical Contractor Licenses Installation Services
Start-up Service and Inspection
Battery Load Testing Maintenance Contracts
24 Hour Emergency Service
Battery Recycling/Disposal