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Engineering LibreTexts

6.9: Secondary batteries

  • Page ID
    21173
  • Secondary (rechargeable) batteries can be recharged by applying a reverse current, as the electrochemical reaction is reversible. The original active materials at the two electrodes can be reconstituted chemically and structurally by the application of an electrical potential between the electrodes to “inject” energy. These batteries can be discharged and recharged many times.

    Applications:

    These fall into two categories:

    (a) The battery is used as an energy storage device. It is constantly connected to an energy source and charged by it. It can then release the stored energy whenever needed, e.g. in

    • Car battery used to start engine
    • Aircraft systems
    • Standby power resources
    • Emergency no-fail systems

    (b) The battery is used as a primary battery would be but is then recharged instead of being disposed of, e.g. in

    • Electric vehicles
    • Mobile phones
    • Cameras
    • Power tools
    • Toys
    • Portable computers

    Advantages:

    • High power density
    • High discharge rate
    • Good low temperature performance

    Disadvantages:

    • Lower Energy density
    • Poorer charge retention
    • Safety issues
    • Lack of standards
    • High initial costs

    The table below demonstrates the properties of various rechargeable batteries:

    System Nominal Cell Voltage (V) Capacity (Wh/kg) Advantages Disadvantages Applications
    2.00
    35
    Low cost; good high and low-temperature operation
    Low cycle life; low energy density; poor charge retention
    Cars; lawn mowers; aircraft
    Ni/Cd
    1.20
    30
    Good physical durability; good charge retention; good cycle life
    High cost; memory effect
    Aircraft; emergency power applications
    Ni/Fe
    1.20
    60
    Good physical durability; long cycling and standing life
    Low power and energy density; high self discharge; high cost
    Stationary applications; fork lift trucks
    Ni/Zn
    1.60
    27
    High energy density; low cost; good low-temperature performance
    Poor cycle life
    Electric scooters/bikes; military vehicles
    Zn/AgO
    1.50
    90
    Highest energy density; low self discharge; high discharge rate
    High cost; low cycle life; low performance at low temperatures
    Military equipment eg torpedo propulsion, submarines
    Cd/AgO
    1.20
    55
    High energy density; low self discharge; Good cycle life
    High cost; low performance at low temperatures
    Portable power tools; satellites
    Ni/H2
    1.40
    55
    High energy density; good cycle life; can tolerate over charge
    High initial cost; self discharge proportional to H2 pressure
    Aerospace
    Ag/H2
    1.40
    80
    High energy density; good cycle life
    High cost - limited to military and aerospace applications
    Aerospace
    up to 4.2
    135
    High specific energy; good shelf life; moldable; non-volatile
    High cost; expensive control methods needed for charge/discharge
    Mobile phones

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