JP2008233092A - Method for accelerating depolarization of polarized battery to facilitate battery testing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of identifying a polarized battery, and then rapidly depolarizing the polarized battery, and to bring the battery in an appropriate state allowing a correct battery test after the depolarization. <P>SOLUTION: This method of depolarizing a polarized rechargeable battery by charging includes processes of: (a) discharging the polarized battery to cause reduction of at least 0.1 V in an open circuit voltage; (b) detecting the open circuit voltage for determining the speed of change of the open circuit voltage; and (c) repeating the process (a) when the speed of change exceeds 10 mV/30 sec. The method also includes processes of: (a) discharging the polarized battery; (b) detecting the open circuit voltage; and (c) repeating the process (a) when a voltage-to-battery ratio (voltage per one battery) exceeds 2.13 V. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Field of Invention

  The present invention relates generally to rechargeable batteries, and more particularly to a method for identifying a polarized battery and accelerating the depolarization process of the polarized battery to facilitate battery testing. .

  Immediately after charging any rechargeable battery, especially a lead-acid battery, typically to a value between about 80% and total capacity, the terminal voltage slowly drops to a steady state value after removing the charging current. . The terminal voltage is observed to decay as a result of the battery being polarized. Battery polarization is due to at least two reasons. 1) an adsorbed gas such as hydrogen generated during charging; and 2) a difference in electrolyte concentration between the body of the plate and the pores of the plate. The latter occurs because sulfuric acid is generated during the battery charge cycle.

  In general, polarized batteries tend to depolarize over several hours. Depending on the polarization tightness, the battery can take as long as 8-12 hours to depolarize. FIG. 1 is a graphical representation of battery voltage as a function of time, with the time axis measured in h.

  Therefore, in order to be able to perform a battery test immediately after charging the battery, it is necessary to accelerate the depolarization of the polarized battery.

  The present invention provides a method of first identifying a polarized battery and then rapidly depolarizing the polarized battery. After depolarization, the battery is in an appropriate state that allows accurate battery testing.

  The present invention provides a method of first identifying a polarized battery and then rapidly depolarizing the polarized battery. After depolarization, the battery is in an appropriate state that allows accurate battery testing.

  The present invention is useful for any rechargeable battery, such as lead acid, NiCd and NiMH, to name a few. Further, the present invention relates to US Pat. No. 4,745,349 to Palanisamy et al. “Apparatus and Method for Charging and Testing Batteries”, US Pat. No. 4,876,495 to Palanisamy et al. “Apparatus and Method for Charging and Testing Batteries”. And can be advantageously used with the invention disclosed in US Pat. No. 5,160,880 “Method and Apparatus for Charging and Testing Batteries” to Palanisamy et al. All these patents are hereby incorporated by reference.

  It is necessary to depolarize the battery before measuring the capacity of the battery during testing or before performing other tests that measure the health or characteristics of the battery. If the voltage of the battery exceeds 2.13V / battery or the rate of change of the battery terminal voltage is greater than 10mV / 30s, the battery is sufficiently polarized so that the capacity or other test is performed on the battery Must be depolarized before.

  Referring to FIG. 2, a polarized battery is first required to discharge the voltage resulting from the battery's polarization or surface charge, typically with a current load of about 0.5 to about 1.0% of the battery's current capacity. The battery is depolarized by discharging the battery for about 20 minutes. Preferably, this discharge time is a minimum of 30 seconds. For example, the current discharge of a 100 amp-hour (Ahr) rated battery would be 0.5-1.0 amps for a minimum of 30 seconds. However, this discharge time should not exceed the time to release useful energy stored in the battery plate. The battery discharge continues until the battery terminal voltage drops by approximately 0.1 volts.

When the discharge time has passed, the battery is opened and the voltage is continuously tracked. If the battery is still polarized, its terminal voltage will increase instantly and will drop rapidly past the local maximum as seen in the time span 30. This rate of voltage increase indicates the tightness of the battery's polarization. If the voltage change is larger than 10 mV / 30 seconds, the second discharge 40 can be immediately applied to the battery. Also, if the battery is not very polarized, the battery may be placed in a relaxed state for about 5 minutes before being discharged again. The process of discharging the battery and possibly relaxing the battery in the open circuit continues until the rate of change of the battery open circuit voltage is less than 10 mV / 30 seconds. At that point, the battery is depolarized until it can survive the capacity (corrent ramp) test disclosed in the references incorporated herein.
Example As a first step, the actual capacities of three different lead acid batteries were measured in three cycles. The average of these three cycles was taken as the capacity of each battery. The capacities of batteries 1 to 3 were 24, 49 and 91 amp-hours, respectively. These fully charged batteries were polarized to different degrees by applying a voltage of 13.6, 13.8 and 14 volts to each battery for about 10-15 minutes. Polarized battery detection was performed using the rate of voltage change and the voltage magnitude. By measuring the voltages of several fully charged polarized batteries and determining their capacities, we have found that capacity values are inaccurate when the battery voltage exceeds 2.13V / battery. Was found to exceed acceptable levels. The inventors have also found that when the rate of change of the battery voltage exceeds 10 mV in 30 seconds, the capacity values reported by the techniques disclosed in the references incorporated herein are not accurate. .

  These batteries were depolarized according to the disclosed method. After depolarization, current ramp tests were performed as described in detail in the references incorporated herein. The battery capacity was calculated using the magnitude of the current at which the battery begins to generate gas while ramping up as disclosed in the references incorporated herein. The results are shown in Table 1.

Table 1
Measurement of polarization battery capacity by current ramp method

Display voltage Display capacity Capacity due to discharge Current lamp after depolarization (Volt) Ampere-hour (Ah) Capacity
(Ahr) (Ah)
12 25 24 22
6 50 49 47
6 50 49 50
6 50 49 45
12 100 91 93
12 100 91 91

It is a graph showing time required for a battery to reach a depolarized state. It is a graph showing the terminal voltage of the battery which is attached to the present invention and changes from a polarized state to a depolarized state.

Claims (2)

A method of depolarizing a rechargeable battery polarized by charging,
a. Discharging the polarized battery to produce a decrease in open circuit voltage of at least 0.1 volts;
b. Sensing the open circuit voltage to determine a rate of change of the open circuit voltage;
c. Repeating step a if the rate of change exceeds 10 mV / 30 seconds;
Including methods. A method of depolarizing a rechargeable battery polarized by charging,
a. Discharging the polarized battery;
b. Detecting the open circuit voltage;
c. Repeating step a if the voltage to battery ratio (voltage per battery) exceeds 2.13 V;
Including methods.

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