ne 139 6029g. two dissimilar metals in an electrolyte electrolyte can be also known as a voltaic...
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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)