Smart battery algorithm for reporting battery parameters to an external device

  • US 5,606,242 A
  • Filed: 10/04/1994
  • Issued: 02/25/1997
  • Est. Priority Date: 10/04/1994
  • Status: Expired due to Fees
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First Claim
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1. A smart battery which provides electrical power and which reports predefined battery parameters to an external device having a power management system, said smart battery comprising:

  • (a) at least one rechargeable cell connected to a pair of terminals to provide electrical power to an external device during a discharge mode and to receive electrical power during a charge mode, as provided or determined by said remote device,(b) a data bus for reporting predefined battery identification and charge parameters to the external device,(c) an analog means for generating analog signals representative of battery voltage and current at said terminals, and an analog signal representative of battery temperature at said cell,(d) a hybrid integrated circuit (IC) having a microprocessor for receiving the analog signals and converting them to digital signals representative of battery voltage, current and temperature, and calculating actual charge parameters over time from said digital signals, said calculations including one calculation according to the following algorithm;

    
    
    space="preserve" listing-type="equation">CAP.sub.rem =CAP.sub.rem -Σ

    I.sub.d Δ

    t.sub.d -Σ

    I.sub.s Δ

    t.sub.s +Σ

    ε

    .sub.c I.sub.c Δ

    t.sub.c wherein CAPrem is remaining battery capacity, CAPFC is full charge battery capacity, Id is battery discharge current, Δ

    td is a period of time of the discharge current Id, Is is battery self discharge current and is a function of battery temperature and CAPFC, Δ

    ts is a period of time of the self discharge current Is, ε

    c is a charging efficiency factor and is a function of battery current and temperature, Ic is battery charging current, and Δ

    tc is a period of time of the charging current Ic,(e) a data memory defined within said hybrid IC for storing said predefined battery identification and actual charge parameters, even when nominally fully discharged, said charge parameters including at least full charge capacity and remaining capacity, and(f) a bus controller defined within said hybrid IC for sending battery messages to said remote device over said data bus, said messages including said predefined battery identification and said actual charge parameters.

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