lead acid batteries l.
Skip this Video
Loading SlideShow in 5 Seconds..
Lead Acid Batteries PowerPoint Presentation
Download Presentation
Lead Acid Batteries

Loading in 2 Seconds...

play fullscreen
1 / 35

Lead Acid Batteries - PowerPoint PPT Presentation

  • Uploaded on

Lead Acid Batteries . “The motor that could, the battery that couldn’t”. Review of Previous Concepts. A battery is a box that segregates charges Electrons are stripped from the anode This leaves holes in the valence orbits of the atoms of the anode Electrons are forced on to the cathode

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Lead Acid Batteries' - race

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
lead acid batteries

Lead Acid Batteries

“The motor that could, the battery that couldn’t”

review of previous concepts
Review of Previous Concepts
  • A battery is a box that segregates charges
    • Electrons are stripped from the anode
      • This leaves holes in the valence orbits of the atoms of the anode
    • Electrons are forced on to the cathode
      • This places extra electrons in the valence orbits of the atoms of the cathode
review continued
Review Continued
  • When an anode and cathode are coupled, you have a capacitor
    • Constructed as anode-insulator-cathode
  • If current is allowed to flow from the cathode to the anode, the capacitor will discharge
    • This tends to happen very quickly, so capacitors are not practical for the storage of large amounts of energy
review continued4
Review Continued
  • For a battery to be functional, we must have a way to keep stripping electrons from the anode and adding them to the cathode
    • This is possible through a chemical reaction
  • A battery is nothing but a mechanical assembly designed to extract energy from a chemical reaction
    • What is this similar to?
    • What can we say about the efficiency of lead acid batteries?
potential difference video
Potential Difference Video
  • Watch the video on potential difference
    • What is potential difference?
mechanism of chemical reaction
Mechanism of Chemical Reaction
  • Anatomy
    • Anode
      • Made of lead dioxide PbO2
    • Cathode
      • Made of pure lead Pb
    • Electrolyte
      • Water H2O
      • Sulfuric Acid H2SO4
      • “Poor, poor Willy, he is no more. What he thought was H2O was really H2SO4”
mechanism of chemical reaction continued
Mechanism of Chemical Reaction Continued
  • Physiology
    • H2SO4 breaks apart into two ions when dissolved in H2O
      • H2 forms a positive ion
        • Shortage of electrons in orbits
      • SO4 forms a negative ion
        • Excess of electrons in orbits
    • Ions are not happy
      • Their valence shells aren’t full, or are over full, so they’re unstable
      • Ions will seek out atoms to bond with to fill their shells
mechanism of chemical reaction continued8
Mechanism of Chemical Reaction Continued
  • Physiology of Cathode
    • SO4 negative ions bond with the lead of the cathode
      • This bond forms lead sulfate PbSO4
      • This lead sulfate molecule has an extra electron
      • Because of the extra electrons, the cathode is negative
mechanism of chemical reaction continued9
Mechanism of Chemical Reaction Continued
  • Physiology of Anode
    • SO4 negative ions wants to bond with PbO2
      • The O2 must be dumped for the Pb and the SO4 to bond
      • O2 dissolves in the electrolyte
        • When the O2 leaves, it takes several electrons with it
    • SO4 bonds with Pb creating PbSO4
      • Because the O2 took several electrons, the net result is a shortage of electrons in the anode
      • A shortage of electrons makes the anode positive
mechanism of chemical reaction continued10
Mechanism of Chemical Reaction Continued
  • Physiology of Electrolyte
    • The electrolyte started as H2SO4
      • It gave up the SO4 molecules to the anode and cathode
      • This leaves H2 atoms in the electrolyte
    • The anode started out a PbO2
      • It gave up O2 to the electrolyte
    • The electrolyte now contains three things:
      • H2O
      • H2
      • O2
further reactions in the electrolyte
Further Reactions in the Electrolyte
  • It is our hope that the dissolved H2 and O2 combine into H2O
  • As the battery discharges, the electrolyte goes from mostly H2SO4 to H2O
discharged battery
Discharged Battery
  • Discharged batteries freeze more easily
  • The density of the electrolyte changes
    • We can use a hydrometer to measure the amount of H2SO4 in the electrolyte
    • This is a predictor of state of charge
problems in the electrolyte
Problems in the Electrolyte
  • Sometimes, not all of the H2 and O2 combine into water
    • This results in H2 off gassing
  • H2 is a highly flammable gas, that will ignite with a small spark
    • For this reasons, sparks should be avoided around batteries
  • Question: How do we avoid sparks when jump starting vehicles?
chemical reactions
Chemical Reactions
  • We know that batteries work by chemical reactions
    • Electrons are stripped from the anode
      • Leaves holes in valence shells
      • This lack of electrons makes the anode positive
    • Electrons are placed on the cathode
      • Places extra electrons in the valence orbits of the cathode
      • These extra electrons make the cathode negative
  • How can we predict if two chemicals will react?
    • If we know the pattern, we can figure out other systems
driving force video
Driving Force Video
  • Watch the video on the driving force behind reactions.
    • When will two chemicals react?
    • What are some examples?
    • When will they not?
mechanism of chemical reaction recharging
Mechanism of Chemical Reaction-Recharging
  • Charging a battery simply reverses the discharge process
    • This is possible because energy is added by the charger
    • The current sent through the plates break chemical bonds
      • PbSO4 breaks down into Pb and SO4
      • SO4 is released into the electrolyte
      • Plates return to Pb
mechanism of chemical reaction recharging17
Mechanism of Chemical Reaction-Recharging
  • At the same time, H2O is split into H2 and O2
    • H2 combines with SO4 to form sulfuric acid
    • O2 combines with the Pb in the anode to form lead oxide PbO2
  • The reaction has now been fully reversed, and the battery is recharged
testing state of charge
Testing State of Charge
  • Because some of the H2O in the electrolyte has been converted to H2SO4, the density of the electrolyte increases.
    • This will show up on a hydrometer test
the entire cycle
The Entire Cycle



characteristics of the reaction
Characteristics of the Reaction
  • There are three basic ways to measure the characteristics of the reaction taking place
    • Potential difference developed
    • The rate at which the reaction happens
    • The overall energy released by the reaction
measuring potential difference
Measuring Potential Difference
  • Potential Difference is the amount of “push” that makes the electrons want to flow through the wire
  • “Push” as you will recall is voltage
    • Voltage can be measured with a voltmeter
measuring potential difference continued
Measuring Potential Difference-Continued
  • The potential difference depends on the chemicals reacting
    • The best possible combination is Lithium and Flourine
      • This would produce a potential difference of 5.9 volts
      • These material are unrealistic
    • Common batteries use lead and sulfuric acid
      • These reactants produce 2.1 volts potential difference
getting 12 volts
Getting 12 volts
  • Each cell of a battery produces 2.1 volts
  • Cells are stacked up in series to add voltages
  • 6 cells are stacked to make 12.6 volts in a healthy battery
  • Batteries showing less than 12.6 volts should be charged before further testing
critical question
Critical Question
  • If the chemical reaction produces 12.6 volts, how is it possible to get 9.6 volts under load?
characteristics of the reaction rate
Characteristics of the Reaction - Rate
  • Voltage is not a good predictor of the health of a battery
    • Would a 9 volt battery crank your engine?
      • Why not?
  • What is really important is the power available
  • One definition of power is the rate at which energy is being converted.
characteristics of the reaction rate26
Characteristics of the Reaction - Rate
  • When we measure the power output of the battery, we are measuring the rate at which the chemical reaction is happening.
  • The rate of the chemical reaction determines the electrical power available from the battery.
  • There are a number of factors that affect the rate of a chemical reaction.
chemical kinetics video
Chemical Kinetics Video
  • Watch the video on chemical kinetics.
    • What factors affect the rate of the chemical reaction?
    • How are these factors optimized in lead-acid batteries?
energy content testing
Energy Content Testing
  • Batteries are rated for energy content in Amp-Hours
  • Testing energy content involves measuring current vs. time and voltage vs. time.
  • Current and voltage are then multiplied to find power.
  • Most tests are conducted at a constant current.
energy content testing current
Energy Content Testing- Current
  • Amperage is held constant
energy content testing voltage
Energy Content Testing- Voltage
  • Voltage is allowed to vary throughout the test
  • Test stops when voltage drops to 10.5 volts
energy content testing power
Energy Content Testing- Power
  • Power = Volts X Amps
energy content testing energy
Energy Content Testing- Energy
  • Energy is defined as the potential to do work
  • Energy = Power X Time
  • How is this reflected in the graph?
finding area under the curve
Finding Area Under the Curve
  • How might you find the area under the curve?
  • See if you can figure it out on the worksheet!
energy density
Energy Density
  • Now that you know the energy in the battery, we can calculate energy density.
  • We know that the battery contains about 1.2 kilowatt-hours of energy
  • To make our comparison, it is necessary to convert that number to kilojoules
    • To get kilojoules from kilowatts, multiply by 3600
    • 1.2 kilowatt-hours X 3600 kilowatt-hours per kilojoule = 4,320 joules
energy density continued
Energy Density-Continued
  • To find the energy density, divide the energy content by the mass
    • Our battery has a mass of about 15 Kg
    • 4,320 kilojoules / 15 kilograms = 288 Kilojoules per kilogram
  • Gasoline has an energy density of 46 megajoules per kilogram
  • What can we say about the viability of the lead acid battery in weight sensitive applications?