lead acid batteries in critical applications

8/3/2019 Lead Acid Batteries in Critical Applications

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C&D Confidential information Do not copy or distribute without permission

Lead Acid Batteriesin

Critical ApplicationsFlooded vs. VRLA

Erik Jones

C&D Technologies, Inc.


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Compare VRLA and Flooded lead acid batteries

Explain the design factors and applications

Explain how to choose

Solutions

Objective:


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What is a Stationary Battery?

Energy Storage

Electrochemical

Two dissimilar metals and anacid provide electrical current

PbO2 +Pb + 2H2SO4 -------2PbSO4 + 2H2O

Lead Dioxide + Sulfuric Acid------Lead Sulfate +Water

Lead + ? --------- Water + SulfuricAcid (Electrolyte)

Calcium

Tin

Cadmium Antimony


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Post

Strap

Plate

Vent

Cover

Jar

How are they similar & different?

Separator

VRLAFlooded


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Similarities

VRLA Flooded

Alloy Lead alloy Lead alloy

Grid Lead alloy, solid frame Lead alloy, solid frame

Paste Mixture of lead oxide, acid,and additives

Mixture of lead oxide, acid,and additives

Plate Paste filled grid Paste filled grid

Electrolyte Sulfuric acid Sulfuric acid

Chemistry Positive plate is the lifelimiting member

Positive plate is the lifelimiting member


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What is the design difference?

Acid - both similar H2SO4 used for both

Difference is in acid strength (concentration)

Conducts electricity between plates

(flooded) 1.215 s.g.

UPS (flooded) 1.250 s.g.

Valve-Regulated 1.300 s.g.


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What is the design difference?

Chemical reaction & Gassing

+ -

O2

H2+ -

O2

H2O

VRLAFlooded

O2 and H2 generated during reaction

recombines into water

Recombination rate ~ 98-99%

No special ventilation reqd - regularroom air exchange is sufficient

O2 and H2 generated during reaction

leaves the cell through open vent

Recombination rate ~ 25%

Room ventilation must be considered- regular room air exchange is not

sufficient


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Flame retardency

Jar and cover material choice

Standard cover is PVC LOI > 32, Standard Jar isPolycarbonate

Standard container is SAN LOI ~18

Industry has been content with flame retardant covers only.

Polycarbonate is used primarily for impact strength, not flameretardancy (poly LOI ~26)Limiting Oxygen Index (LOI) is used

to rate the ability to support a flame

LOI refers to the minimum oxygen

level required to sustain a flame. Ifthe LOI is above ~20, the plastic will

be self-extinguishing


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Top lead/post design

Copper inserted post

Copper inserts are usedin UPS and Switchgearcell posts to aid in high

rate discharges

Two hole posts allowdouble connectors foradditional high ratecapability and formaintenanceconnectionsExample: Copper inserted post


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Ventilation

Typical design

requires the volumeof Hydrogen not

exceed 1-2% thevolume of the room

At 4% room volume,

explosive

conditions exist

H2 LEL = 4%


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Flooded VRLA

MAINTENANCE

Electrolyte level check X

Electrolyte gravity check X

Hydrogen gas ventilation X

Connector torque X X

MONITORING

Voltage X X

Float current X X

Temperature X X

Visual - external X X

Visual - internal X

Specific gravity X

Maintain?


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FLOODED VRLARobust Intolerant of abuse & hostile

conditions

Predictable performance Unpredictable failures

Requires more floor space Compact design space savings

Requires active ventilation No special ventilation reqd

Must consider spill containment Typically requires no spill

containment

Requires moderate maintenance& monitoring

Requires some maintenance,moderate monitoring

How to choose?


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How to choose?

Failure Points?

Space considerations480V systems


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Typical VRLA failure modes and causes

Dry out

Caused by excessive float current Caused by vents staying open

Grid Corrosion / growth Caused by excessive float current

Thin plate design

Negative Plate Polarization Negative plate does not get fully charged

Bulging, Jar Cracks Caused by build up of pressure from high float current

Caused by faulty vents


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How do they fail?

Flooded common modes of failure

Positive grid corrosion

Loss of active material

Internal shorts

Loss of electrolyte

Plate sulfation

Hydration


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How to choose?

You must consider the following

Application Cycle vs. float

Discharge rate

Capacity

Estimated service life vs. Warranty

Temperature Power Quality and System Design

Space & Accessibility Building Codes, Footprint, environment

Maintenance & Monitoring

COST


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0

100000

200000

300000

400000

500000

600000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Years

Cumulative

Dollars

Flooded appx 120 sq ft

12V Monoblc appx 68 sq ft

Traditional 2V VRLA

Appx 72 sq ft

Total Cost of Ownership

750KVA System 15 Minute Runtime

DOES NOT INCLUDE SPACE, COOLING, and ENERGY COSTS


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Energy Efficient?

Reduce float current

Manage the recombinationprocess

Balanced pos & neg

active materialsprocess/design

Optimize Electrolyte

design and control Control oxygen transfer

through separator

Engineered separator &

plate porosity control -

reactivity0

5

10

15

20

25

30

35

40

45

50

Typical

VRLA2V Hybrid Flooded

Cell Type

FloatCurrentm

A/100A-hr


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Selection

Planning: The system environment will have a profoundaffect on the type of battery selected and its reliability

SystemInputs

Power Quality Conditioning

Cycles over life

PowerRequirementsSystem SizeBattery Type

Site LayoutAvailable Space

Dedicated roomSystem Access

EnvironmentTemperature ControlSystem Protection

Regulatory

CriticalityRedundancyGenerators/Engine

StartMaintenance Interval


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Sizing for UPS System Batteries

What you should know before you start!

Battery load in Watts (Kilowatts) Load duration in minutes

END VOLTS vs. Runtime

Initial Capacity

DC buss voltage / number of cells

Inverter input minimum operating voltage

Inverter efficiency

Operating temperature

Sized to 77F

Rectifier float & maximum output VDC

Redundancy requirement

Desired Life and Warranty Power Quality


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% Capacity vs. Reserve Time

Estimated % Capacity vs. Reserve Time

For a Battery Sized to Provide 10 minutes at 100% Capacity

80%

85%

90%

95%

100%

105%

0 2 4 6 8 10 12Reserve Capacity (minutes)

%

Capacity

80% capacity is NOT 80% of reserve time!


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Commissioning

IEEE

450 1188

Capacity Testing

I and O Manual Equalize

Float Connections

Customer Standards Cabling

NEC AC Input

Experience


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Battery recycling Green Option

Battery Components 100% Recyclable

Over 97% of used lead-acid batteries are recycled

One of the most recycled components

Well established channels exist to ensure proper

disposal of Lead-acid batteries Lead, plastic, and sulfuric acid can be recycled and

reused

Recycled components reused

Source: BCI website


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Questions?

THANK YOU

Erik Jones

(909) 201-4440

[email protected]

lead acid batteries in critical applications

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