System and method for battery charging

• US 20050017684A1
• Filed: 10/03/2001
• Published: 01/27/2005
• Est. Priority Date: 10/03/2001
• Status: Active Grant

• Current Assignee: Trojan Battery Company
• Original Assignee: Trojan Battery Company
• Inventors: Brecht, William B
• Granted Patent: US 7,129,675 B2
• Time in Patent Office: Days
• US Class Current: 320/131
• 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 deep cycle lead acid batteries comprising:

applying charging energy to such a battery;

identifying a 98% charge point in the charging process;

monitoring the charging energy provided in amp hours;

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 a point of full charge of the battery; and

applying the remaining charging energy to the battery.

2. The method of claim 1 for charging a deep cycle lead acid battery wherein the step of determining the 98% charge point comprises:

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

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

3. The method of claim 1 for charging a deep cycle lead acid battery wherein the step of determining the remaining charging energy comprises:

dividing the product of 0.98 and the charging energy applied to charge the battery to 98% of its charge capacity by a decimal equivalent of the percent of overcharge desired.

4. A method for charging flooded deep cycle lead acid batteries comprising the steps of applying charging energy to such a battery according to a selected charging profile;

identifying the point in the process at which the battery state has a known relation to a state of full charge of the battery and determining a first amount of charging energy delivered to the battery from the inception of the process to that point;

determining a second amount of further charging energy, adequate when applied to the battery to cause the battery to be overcharged by a selected amount related to the first amount; and

applying the second amount of charging energy to the battery.

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

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

applying to such a battery an amount of charging energy equal to the initial charge deficiency of the battery, and

applying to the battery a further increment of charging determined from information developed from the battery during performance of the method, adequate to overcharge the battery to an extent predetermined as a selected percentage of the charge deficiency.

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

a DC current source;

a device operative to quantify the amount of charging energy delivered to a battery from the beginning of a pertinent battery recharge event;

a dv/dt measurement circuit; and

a d²v/d^t2 measurement circuit

8. Apparatus according to claim 7 including a controller coupled to the DC current source and the dv/dt and d²v/dt² measurement circuits, the controller being configured for determining the point in a battery recharge event when a battery is at substantially a defined 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 point at which the battery has substantially the defined percentage of full charge, p is the decimal equivalent of the defined 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 ampere-hours to be delivered to the battery from the beginning of the recharge event to reach the overcharge amount.

9. Apparatus according to claim 8 in which the value of p is substantially 0.98.

10. An apparatus according to claim 8 in which x is in the range of from about 0.08 to about 0.12.

11. An apparatus for charging deep cycle lead acid batteries, the improvement comprising the combination which includes a voltage measurement device, a current measurement device, a timer, and a mechanism operative for determining when a battery being charged by the apparatus is at that point in a charging event at which the battery has a predetermined state of charge at or less than full charge and for determining and controlling the application to the battery beyond that point of a 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 point in that charging event.