System and method for battery charging

• US 7,129,675 B2
• Filed: 10/03/2001
• Issued: 10/31/2006
• Est. Priority Date: 10/03/2001
• Status: Expired due to Fees

• Current Assignee: Trojan Battery Company
• Original Assignee: Trojan Battery Company
• Inventors: Brecht, William B.
• Primary Examiner(s): Easthom, Karl
• Assistant Examiner(s): BOATENG, ALEXIS ASIEDUA
• Application Number:
  US10/491,306
• Publication Number:
  US 20050017684A1
• Time in Patent Office: 1,854 Days
• Field of Search: 320/156, 320/161, 320/148, 320/137, 320/131, 320/130, 324/426, 324/427
• US Class Current: 320/137
• CPC Class Codes: H01M 10/06 Lead-acid accumulators semi-lead accumulators H01M10/20
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/446 Initial charging measures
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method for charging a lead acid storage battery to advantageously extend its life is described. The termination of a charging process is based upon an evaluation of the first derivative (dv/dt) and second derivative (d2v/dt2) of the applied charging voltage. By utilizing the first derivative (dv/dt) and second derivative (d2v/dt2) as charging criteria, an amount of overcharge is applied to the battery that takes into account the precise amount of amp-hours previously removed from the battery. A charger arrangement for performing a charging process of the invention also is described.

Claims

1. A method for charging flooded deep cycle lead acid batteries comprising the steps of:

applying charging energy to such a battery;

monitoring the charging energy as to quantity delivered to the battery and its dv/dt and d²v/dt² aspects;

by use of information about a first amount of charging energy delivered to the battery to a point in the process when dv/dt is a maximum and d²v/dt²=0, determining at that point and delivering to the battery beyond that point a defined quantity of charging energy additive to said first amount adequate to overcharge the battery to a predetermined extent related to said first amount.

2. A method for charging flooded deep cycle lead acid batteries comprising the steps of:

applying to such a battery a first amount of charging energy adequate, in combination with an initial charge condition of the battery, to cause the battery to attain a detectable charge state which is less than a full charge condition and which has a known relation to a full charge condition, and

applying to the battery a further second increment of charging energy which is adequate, in combination with the initial charge condition and the first amount of charging energy, to overcharge the battery to a selected extent and the quantity of which is determined as a selected percentage of the first amount of charging energy when the detectable charge state is attained.

3. The method as claimed in claim 2 in which the detectable charge state is the state at which the battery is at substantially 98% of full charge.

4. The method as claimed in claim 3 in which the step of determining the amount of the further second increment of charging energy includes:

dividing a) the product of (i) first amount of charging energy and (ii) the sum of unity (one) and the decimal equivalent of the percent of overcharge by b) 0.98.

5. The method as claimed in claim 4 in which the step of determining the amount of the second increment of charging energy further includes determining the difference between a) the result of the division operation described in claim 4 and b) the first amount of charging energy.

6. The method as claimed in claim 2 in which the detectable charge state is detected by:

determining when the rate of change of an applied charging voltage with respect to time (dv/dt) is a maximum; and

determining when the acceleration of the applied charging voltage with respect to time (d²v/dt²) is zero.

7. A method for charging deep cycle lead acid batteries comprising:

applying charging energy to such a battery;

detecting a point of 98% of full charge in the charging process;

monitoring the charging energy provided in amp hours to attain the 98% full charge point;

determining the remaining charging energy to be applied to fully charge the battery and to overcharge the battery by an amount substantially equal to a predetermined percentage of the quantity of energy applied to the battery from the commencement of charging to the 98% full charge point of the battery; and

applying the remaining charging energy to the battery.

8. The method of claim 7 for charging a deep cycle lead acid battery wherein the step of detecting the 98% full charge point comprises:

determining when the rate of change of an applied charging voltage with respect to time (dv/dt) is a maximum; and

determining when the acceleration of the applied charging voltage with respect to time (d²v/dt²) is zero.

9. Apparatus for charging flooded deep cycle lead acid batteries which includes a DC source, a mechanism operable to measure the amount of charging energy delivered to a battery from the beginning of a battery charging event, and a mechanism operative for detecting when a battery being charged by the apparatus is at a detectable point in a charging event at which the battery has a certain state of charge less than full charge and for determining at that point and controlling the application to the battery beyond that point of a further quantity of charging energy effective to overcharge the battery by a selected percentage of the amount of charging energy delivered to the battery to that detectable point in that charging event.

10. Apparatus as claimed in claim 9 further including:

a dv/dt measurement circuit, a

d²v/dt² measurement circuit, and

a controller coupled to the dv/dt and d²v/dt² measurement circuits, the controller being configured for detecting the point in a battery recharge event at which dv/dt is a maximum and d²v/dt²=0, and at which the battery is at substantially a certain percentage of full charge, and for determining the value of Q_D from the relation Q_S/p =Q_D/(1+x) in which Q_S is the ampere-hours of charging energy delivered to the battery in the interval from the beginning of the recharge event to the detected point, p is the decimal equivalent of the certain percentage, x is the decimal equivalent of a desired percentage amount of replenishment charge to be delivered to the battery as an overcharge amount, and Q_D is the total amount of charging energy to be delivered to the battery from the beginning of the recharge event to the end of that event.

11. Apparatus according to claim 10 in which the value of p is substantially 0.98.

12. Apparatus according to claim 10 in which x is in the range of from about 0.08 to about 0.12.