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Cordless dual-battery electric tool

  • US 5,028,858 A
  • Filed: 12/01/1989
  • Issued: 07/02/1991
  • Est. Priority Date: 12/28/1988
  • Status: Expired due to Fees
First Claim
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1. A cordless electrical tool comprising:

  • a housing forming first and second battery mounts;

    an electrical motor in the housing;

    first and second batteries removably carried in said first and second mounts, respectively;

    said batteries being connected in series with each other and across said motor;

    a cutoff switch connected in series between said batteries and said motor and openable to electrically disconnect said motor from said batteries; and

    means including a control circuit for detecting the charge level of each said battery and opening said cutoff switch when the charge level of either said battery drops below a predetermined threshold, said control circuit having first and second light-emitting diodes associated with said first and second battery mounts and hence with said first and second batteries, respectively, and means for turning either said diode on when the charge level of its said associated battery drops below said predetermined threshold, thus to provide visual indication of which said battery needs replacement.

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