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Electrical supply control system for a motor vehicle

  • US 5,272,380 A
  • Filed: 03/08/1991
  • Issued: 12/21/1993
  • Est. Priority Date: 09/09/1988
  • Status: Expired due to Fees
First Claim
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1. A control system for the electrical supply of a motor vehicle, the motor vehicle incorporating an electrical storage battery and electrical system including at least one facility which normally consumes current when the vehicle is left unattended and driver operable switch means such that a first switching operation normally occurs when the driver leaves the vehicle and a second switching operation normally occurs when the driver returns to the vehicle;

  • the control system comprising means for generating a first relatively low reference voltage selected to conform to a pre-selected battery condition;

    a first timing means operable for a relatively short period;

    means responsive to said first switching operation to start the first timer;

    first voltage comparison means arranged to compare the actual battery voltage with the first reference voltage after said relatively short period and thereafter to provide a low battery signal if the actual voltage is below the first reference voltage;

    means for isolating the battery from the electrical system in response to the low battery signal and means for reconnecting the battery to the electrical system in response to said second switching operation, characterised by the provision of means for generating a second relatively high reference voltage selected to conform to a different pre-selected battery condition;

    a second timing means operable for a relatively long period and responsive to the first switching operation to start the second timer;

    second voltage comparison means arranged to compare actual battery voltage with the second reference voltage after said relatively long period and thereafter to provide a low battery signal if the actual voltage is below the second reference voltage;

    the means for isolating the battery from the electrical system being responsive to either low battery signal.

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