NE 1396029G

Two dissimilar metals in an electrolyte Electrolyte can be

Also known as a voltaic cell Only able to be used once

Primary Cells

RevisionRevision

Alkali (Base)Acid

Salt

Can’t be recharged

Primary Cells

RevisionRevision

Dependant on electrode type

Dependant surface area of electrode

Cell Voltage:

Cell Current:

Suffers from:“Local Action”“Polarisation”

Plates generally are of the same material Electrolyte is:

Chemical reaction is reversible

Secondary CellsSecondary Cells

• Acid• Alkali (Base)

Plante CellPlante CellDeveloped by Raymond Gaston Plante

1834 - 1889

Lead (Pb) Lead (Pb)

Sulphuric Acid (H2SO4)

Chemical ProcessChemical ProcessCharged Discharged

Pb + HSO4+ + H2O

Anode

Cathode

PbO2 + 3H3O+ + HSO4- + 2e-

PbSO4 + H3O+ + 2e-

PbSO4 + 5H2O

Lead Sulphuric Acid

Water

Lead Peroxide

Lead Sulphate

Acid No AcidCell Voltage = 2V

CharacteristicsCharacteristicsCharged∙ Anode or Negative plate Lead

∙ Cathode or Positive plate Lead peroxide (Brown)

∙ Acid as electrolyte

Discharged∙ Both Negative & Positive plates Lead

Sulphate

∙ Water as electrolyte

Lead is soft, plates distorted easily

Amps/m2 small, surface area needed to be increased (post card size only produces 1 Amp)

Plates change size as they take on sulphate

Cannot remain uncharged as Sulphate crystals grow (can’t be converted back)

PlantPlantéé Cell Problems Cell Problems

Pasted Platé Cell (Faure Cell)

Developed by Camille Alphonse Faure (1840 - 1898)

1880coated lead plates with a paste of lead oxides, sulphuric acid and water, which was then cured. The curing process caused the paste to change to a mixture of lead sulphates

1881Plates were perforated to provide a key for paste and to increase surface area

Red lead

Pb3O4

Cast perforated lead plate

Pasted lead plate

Separator

Modern Lead Acid BatteriesModern Lead Acid Batteries

Additives alloyed with lead to increase strength may include:

• Antimony• Tin• Calcium• Selenium

Plates are made thin and stacked to increase current outputNumber of plates indicate cells output

Variations to Lead Acid Variations to Lead Acid BatteryBattery

Designed to provide high currents for short periods of time :- CC (Cranking Current)

DischargeTypical = 5-10% of capacityMaximum = 20% of capacity

Standard Automotive Batteries

Variations to Lead Acid Variations to Lead Acid BatteryBattery

Designed to provide Low currents for long periods of time

DischargeMaximum = 80% of capacity

Standard Automotive BatteriesDeep Cycle batteryDeep Cycle battery

Plates are thicker & may be solid construction

Variations to Lead Acid Variations to Lead Acid BatteryBattery

Designed to start motors and provide some low currents for periods of time

DischargeMaximum = 50% of capacity

Standard Automotive BatteriesDeep Cycle batteryDeep Cycle battery

Plates standard construction but are thicker

Hybrid, or Marine batteryHybrid, or Marine battery

Variations to Lead Acid Variations to Lead Acid BatteryBatteryStandard Automotive BatteriesDeep Cycle batteryDeep Cycle battery

Hybrid, or Marine batteryHybrid, or Marine battery

Maintenance Free or VRLA Maintenance Free or VRLA batterybattery

Maintenance Free/VRLA Maintenance Free/VRLA BatteryBattery

Valve Regulated Lead Acid • Absorbent glass mat (AGM)

• Gel Cell

Chemical reaction causes release of:

• Hydrogen• Oxygen

Recombination of Gasses Replacement of Antimony

Increasing the capacity of the negative plate

• Calcium• Selenium• Tin

Negative plate gives off Hydrogen when fully charged

If area of –ve plate is larger than +ve plate it will never reach full charge.

Absorbent glass mat (AGM)Absorbent glass mat (AGM)electrolyte is absorbed into a mat of fine glass fibres

like wet cell lead acid battery in a rectangular case

• wound plates are thin

• lead in their plates are purer as they no longer need to support their own weight

• internal resistance is lower than traditional cells due to close plate proximity and the pure lead plates have lower resistivity

• Flat

• Cylindrical/Spiral

Gel CellGel Cell• Sulfuric acid is mixed with a silica fume, which

makes the resulting mass gel-like and immobile

• Do not need to be kept upright (though they cannot be charged inverted).

• Virtually eliminate the electrolyte evaporation, spillage (and subsequent corrosion issues) common to the wet-cell battery

• Often referred to as sealed lead-acid (SLA) batteries

• Antimony in the lead plates is replaced by calcium

• often referred to as a lead-calcium battery

Nickel IronNickel Iron

Negative / Anode:

Positive / Cathode: Nickel oxide-hydroxide

Iron

Electrolyte: Potassium hydroxide

Cell Voltage: 1.2 Volts

Nickel IronNickel IronInvented by: Waldemar Jungner 1899

Developed by: Thomas Edison 1901

Also invented the Nickel-Cadmium battery

1903 to 1972 by the Edison Battery Storage Company

1972 the battery company was sold to the Exide Battery Corporation which discontinued making the battery in 1975

Only manufactured in china as of 2008

Nickel IronNickel IronAdvantages

• Very long life ≈ 20Years • Tolerant of abuse• Plates do not corrode like Lead Acid• Can be left discharged• Does not contain dangerous chemicals

• Overcharge• over-discharge• short-circuiting• thermal shock

Disadvantages• Low energy to weight ratio • Slow to take/ deliver charge• More expensive than lead acid

1.-1 hr discharge rate2.-2 hr discharge rate3.-3 hr discharge rate4.-4 hr discharge rate5.-8 hr discharge rate6.-10 hr discharge rate7.-20 hr discharge rate8. Normal charge9. Rapid charge

Nickel Cadmium

Problem where the Ni-Cd battery would remember the amount of discharge for previous discharges and limit the recharge life of the battery

Memory effectMemory effect

Crystal growth can occur when a modern Ni-Cd battery is recharged before it is fully discharged. The crystal growth can eventually prevent the battery from discharging beyond that point and/or cause rapid self-discharge of the battery

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Cell ConfigurationsCell Configurations SeriesSeries

ParallelParallel

Series/Series/ParallelParallel

Higher voltage than a single cell can supply

Higher current than a single cell can supply

Higher voltage & current than a single cell can supply

2 Volt0.5 A

2Total Voltage =

46

Total Current = 0.5 A

2 Volt0.5 A

Total Voltage =

2

Total Current =

0.51.01.5

Cell Internal Cell Internal ResistanceResistance

Materials used in the cell Surface area of the electrodes Distance between the electrodes Operating temperature of the cell Cells state of charge

Dependant upon:

Look at this next lesson

Limit in the maximum current that can be supplied by the cell

Terminal voltage drops as current increases

Cell Internal Cell Internal ResistanceResistance

Causes a:

2V

0.2 2/0.2 =10 Amps

Ri

2.0 2/2 =1 Amp

20 2/20 =0.1 Amp

Maximum Maximum CurrentCurrent

2V

0.2 2-(0.2 x 0.1) =1.98 Volts

Ri

2.0 2-(2 x 0.1) = 1.8 Volts

20 2-(20 x 0.1) = 0 Volts

Terminal Terminal VoltageVoltageLoad Current = 0.1 Amp

Internal Resistance in Internal Resistance in BatteriesBatteries Parallel connected

CellsRi

Ri = 0.1

Ri = 0.10.050.033

Ri = 0.033

V = 2 V

V = 2 V

Number of cells

Internal Resistance in Internal Resistance in BatteriesBatteries Series/Parallel connected Cells

Ri x Number of series cells in branch

Ri =

Ri = 0.15

V = 6 V

V = 6 V

Number of Branches

Ri = 0.3

0.3

20.15

Cell Capacity Cell Capacity MeasurementMeasurement

CCACCA

CACAmeasurement of the number of amps a battery can deliver at -17° C for 30 seconds and not drop below 7.2 volts

Cold Cranking Amps

measured at 0° C. This rating is also called Marine Cranking Amps.

Cranking Amps

Hot Cranking Amps is seldom used any longer but is measured at 26.7°C

Cell Capacity Cell Capacity MeasurementMeasurement

CCACCA

CACA

RCRC

AHAH

Cold Cranking Amps

Cranking Amps

the number of minutes a fully charged battery at 26.7° C will discharge 25 amps until the battery drops below 10.5 volts.

Reserve Capacity

If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours

Amp Hour

Amp Hour RatingAmp Hour RatingStandard lengths of time are 10 or 20

Hours

100Ah battery should supply:

1 Amp for 100 Hours2 Amps for 50 Hours5 Amps for 20 Hours10 Amps for 10 Hours

10 hours for standard batteries

20 hours for deep cycle batteries

100 Amps for 1 Hour

Not possible as battery may not be able to deliver this

current

Decreasing the discharge period decreases the AH output of the battery

Battery Battery ChargingCharging

Cell ChargingCell Charging Appling a voltage that is larger than the cells

terminal voltage

Current then flows in the opposite direction

Chemical change takes place

Energy is stored as a chemical change

Cell Internal Cell Internal ResistanceResistance

Materials used in the cell Surface area of the electrodes Distance between the electrodes Operating temperature of the cell Cells state of charge

Dependant upon:

Cell Internal Cell Internal ResistanceResistance

Increases as cell discharges

Decreases as cell charges

Cell Capacity Cell Capacity MeasurementMeasurement

CCACCA

CACA

RCRC

AHAH

Cold Cranking Amps

Cranking Amps

Reserve Capacity

Amp Hour

How do we measure Cell How do we measure Cell Capacity?Capacity?

Measurement of open circuit terminal voltage

Measuring the acid concentration

Placing the battery under a controlled load

Coulomb counting

Electrochemical Impedance Spectroscopy

Voltage MeasurementVoltage Measurement

Cell Type Cell temperature Cell age Time since last charge

Factors to consider:

ElectrolyteTemperature

(Celsius)

100%SoC

75%SoC

50%SoC

25%SoC

0%SoC

48.9° 12.663 12.463 12.253 12.073 11.903

43.3° 12.661 12.462 12.251 12.071 11.901

37.8° 12.658 12.458 12.248 12.068 11.898

32.2° 12.655 12.455 12.245 12.065 11.895

26.7° 12.650 12.450 12.240 12.060 11.890

21.1° 12.643 12.443 12.233 12.053 11.883

15.6° 12.634 12.434 12.224 12.044 11.874

10.0° 12.622 12.422 12.212 12.032 11.862

4.4° 12.606 12.406 12.196 12.016 11.846

-1.1° 12.588 12.388 12.178 11.998 11.828

-6.7° 12.566 12.366 12.156 11.976 11.806

-12.2° 12.542 12.342 12.132 11.952 11.782

-17.8° 12.516 12.316 12.106 11.926 11.756

Lead Acid

ElectrolyteTemperature

(Celsius)

100%SoC

75%SoC

65%SoC

50%SoC

25%SoC

0%SoC

48.9° 12.793 12.563 12.463 12.313 12.013 11.773

43.3° 12.791 12.561 12.461 12.311 12.011 11.771

37.8° 12.788 12.558 12.458 12.308 12.008 11.768

32.2° 12.785 12.555 12.455 12.305 12.005 11.765

26.7° 12.780 12.550 12.450 12.300 12.000 11.760

21.1° 12.773 12.543 12.443 12.293 11.993 11.753

15.6° 12.764 12.534 12.434 12.284 11.984 11.744

10.0° 12.752 12.522 12.422 12.272 11.972 11.732

4.4° 12.736 12.506 12.406 12.256 11.956 11.716

-1.1° 12.718 12.488 12.388 12.238 11.938 11.698

-6.7° 12.696 12.466 12.366 12.216 11.916 11.676

-12.2° 12.672 12.442 12.342 12.192 11.892 11.652

-17.8° 12.646 12.416 12.316 12.166 11.866 11.626

Lead Acid (Ca)

ratio of the density of a given solid or liquid substance to the density of water at a specific

temperature and pressure.

Acid Concentration Acid Concentration MeasurementMeasurementSpecific Gravity

Generally at 4°C and 1 atmosphere

Battery Standard = 30° CBattery Standard = 30° C

Can’t be measured on Alkaline Can’t be measured on Alkaline cellscells

ElectrolyteTemperature

(Celsius)

100%SoC

75%SoC

50%SoC

25%SoC

0%SoC

48.9° 1.249 1.209 1.174 1.139 1.104  

43.3° 1.253 1.213 1.178 1.143 1.108  

37.8° 1.257 1.217 1.182 1.147 1.112  

32.2° 1.261 1.221 1.186 1.151 1.116  

26.7° 1.265 1.225 1.190 1.155 1.120  

21.1° 1.269 1.229 1.194 1.159 1.124  

15.6° 1.273 1.233 1.198 1.163 1.128  

10.0° 1.277 1.237 1.202 1.167 1.132  

4.4° 1.281 1.241 1.206 1.171 1.136  

-1.1° 1.285 1.245 1.210 1.175 1.140  

-6.7° 1.289 1.249 1.214 1.179 1.144  

-12.2° 1.293 1.253 1.218 1.183 1.148  

-17.8° 1.297 1.257 1.222 1.187 1.152  

Controlled Load TestingControlled Load Testing 3 x of batteries AH rating is placed across

terminals After 15 - 20 seconds terminal voltage is

measured The higher the voltage the better the battery Voltage should not be less than 9.6V

OR ½ x CCA of Battery

1.6 V

Coulomb Counting Coulomb = Current and Time Computerised Current is measured going into and out of the

battery

Injects Multiple frequencies ranging from 20-2,000 Hertz.

The signals are regulated to very low voltages The results are computer analysed to determine

batteries capacity

Electrochemical Electrochemical ImpedanceImpedance

SpectroscopySpectroscopy

Cell ChargingCell Charging Appling a voltage that is larger than the cells

terminal voltage

Current then flows in the opposite direction

Chemical change takes place

Energy is stored as a chemical changeCompromise between

Plate (Grid) Corrosion or SulfationHigh Voltage Low Voltage

2.45 V 2.30 V

Types of Battery Types of Battery ChargersChargers

Type dependant on how the battery is used

Permanently Connected

Isolated to be charged

Types of Battery Types of Battery ChargersChargers

FloatFloatOutput Voltage lower than normal charges to

reduce danger of over charging

Output Current supplied at very low levels, but above leakage currents

Lead Acid

Lead Acid (Ca)

Lead Acid (AGM)

Lead Acid (Gel)