Lithium ion battery unit adapted to be charged by an alkaline charger

• US 6,304,063 B2
• Filed: 01/26/2001
• Issued: 10/16/2001
• Est. Priority Date: 02/03/2000
• Status: Expired due to Fees

• Current Assignee: Saft Finance Sarl (Totalenergies Se)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Boisumault, Philippe, Jaud, Stéphane, Maloizel, Serge
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/769,357
• Publication Number:
  US 20010011882A1
• Time in Patent Office: 263 Days
• Field of Search: 320/127, 320/128, 320/132, 320/134, 320/136
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

A battery unit includes at least one storage cell, two external connecting terminals, one of which is positive and the other of which is negative, and a safety circuit connected to prohibit entry of charging current into the cell as soon as a voltage applied between the external connecting terminals is greater than a particular maximum safety voltage. An additional protection circuit is connected between the external terminals and the safety circuit to prohibit the entry of charging current into the safety circuit as soon as the voltage applied between the external connecting terminals is greater than a particular maximum charging voltage which is less than the maximum safety voltage. This prevents the safety circuit operating unnecessarily.

Claims

1. A battery unit including at least one storage cell, two external connecting terminals, one of which is positive and the other of which is negative, and a safety circuit connected to prohibit entry of charging current into said cell as soon as a voltage applied between said external connecting terminals is greater than a particular maximum safety voltage, in which battery unit an additional protection circuit is connected between said external terminals and said safety circuit to prohibit the entry of charging current into said safety circuit as soon as said voltage applied between said external connecting terminals is greater than a particular maximum charging voltage which is less than said maximum safety voltage.

2. The battery unit claimed in claim 1 wherein said additional protection circuit includes a MOSFET switch which is controlled to prohibit or authorize entry of a charging current into said safety circuit.

3. The battery unit claimed in claim 2 wherein said switch is controlled by a comparator having a first input which receives said maximum charging voltage and a second input which receives said voltage applied to said external connecting terminals and said second input is connected to said external connecting terminals by a divider bridge having a division ratio which varies to introduce hysteresis into the control of said switch.