CS241355B1 - Method of experimental capacity determination of nickel-cadmium accumulators with dropping electrodes - Google Patents

Abstract

The problem of determining the capacity of nickel-cadmium is addressed rechargeable batteries. The essence of the solution lies in the possibility of finding out capacities of nickel-cadmium batteries when charging them. When charging Ni-Cd batteries Charging takes place first cadmium electrodes. After charging the cadmium electrode there is a sharp rise in tension Ni-Cd battery that is related to the transition for ineffective overcharging of the cadmium electrode associated with significant developments hydrogen. The capacity of Ni-Cd batteries is here corresponds to the time when the battery being evaluated reaches the charging voltage value that is ranges from 1.45 to 1.80 V. Value the capacities of the measured Ni-Cd cells are then determines the product of this time and current, charging the battery. The method can be used to determine capacity all types of nickel-cadmium batteries pocket construction.

Description

accumulators with pocket electrodes

The problem of determining the capacity of nickel-cadmium accumulators during their charging is solved.

The essence of the solution lies in the possibility of determining the capacity of nickel-cadmium accumulators during their charging. When charging Ni-Cd batteries, the cadmium electrode is effectively charged first. When the cadmium electrode is charged, the Ni-Cd accumulator voltage rises sharply as a result of the transition to ineffective overcharging of the cadmium electrode, which is associated with significant hydrogen evolution. The capacity of Ni-Cd accumulators corresponds to the time when the evaluated accumulator reaches the value of the charging voltage, which ranges from 1.45 to 1.80 V. The value of the capacity of the measured Ni-Cd cells is then determined from the product of this time and current, which is rechargeable battery.

The method can be used to determine the capacity of all types of nickel-cadmium batteries of the pocket construction.

The invention relates to a method for experimentally determining the capacity of nickel-cadmium accumulators with pocket electrodes.

The capacity of nickel-cadmium accumulators with pocket electrodes, usually expressed in θ / ο of the rated capacity stated by the manufacturer, means the Ah-capacity of these accumulators obtained during the capacity test performed according to CSN 354 »350 ST SEV.

Users of nickel-cadmium accumulators or organizations providing, in the course of normal, medium or general overhaul of equipment containing such accumulators, also checking the capacity of the accumulators associated with the replacement of their electrolytes, mostly in a different way, in particular with respect to and resulting capacity of evaluated accumulators.

According to CSN 364 350 ST SEV, the capacity of nickel-cadmium accumulators with pocket electrodes is determined from the product of constant discharge current I and time t corresponding to the time when the accumulator reaches a final voltage value of 1.0 V or lower according to the discharge current, and the ambient temperature at which the battery capacity is measured.

However, during the measurement of the capacity of a large number of series-connected nickel-cadmium accumulators, due to the rapid voltage drop of the rated accumulators towards the end of discharge, ie from 1.15 V, most users terminate the capacity measurement measurements when reaching 1.10 V / accumulator . The main reason is the increased instability of the discharge current during a portion of the discharge curve and at the same time the difficulty of quickly performing the required disconnection of those accumulators that have reached the final discharge voltage, leading to a significant reduction in the accuracy of battery capacity determination.

These inaccuracies could be partially eliminated by the gradual automatic switch-off of the battery discharge, which reached the desired end of the discharge voltage, but this is not feasible for most users of nickel-cadmium accumulators, because such a demanding device is not produced in our country.

For this reason, most users of pocket-size nickel-cadmium accumulators measure their capacity during operation in essentially two ways:

either using a 1.10 volt voltage as the final discharge voltage for evaluating the capacity of the nickel-cadmium accumulators or evaluating the battery capacity from the voltage achieved after 3.5 hours of discharge at the desired value, ie after 70% of the specified capacity using nickel-cadmium accumulators with pocket electrodes.

In both cases, although greater stability of the discharge current is ensured during the discharge of a plurality of measured accumulators of different capacities, the error resulting from the need to interrupt the discharge when disconnecting the accumulators that reached the final discharge voltage value is not eliminated.

In addition, the two methods described do not allow the exact capacity values of the measured accumulators to be determined, or the accumulators are not discharged up to 1.0 V (possibly below) as required by CSN 36 4350. This does not allow rebuilding the accumulator battery from accumulators of identical capacity. which must always be performed after the test has been carried out in order to avoid a rapid decrease in the capacity of those batteries of the battery system which show significantly lower capacitance values compared to the other batteries of the system during the lifetime of the batteries.

The above-mentioned inaccuracies and existing problems for users are eliminated by the method of experimental determination of capacity of nickel-cadmium accumulators with pocket electrodes according to the invention, which consists in the first discharge of nickel-cadmium accumulators to voltage 1.0 V, followed by charging of measured accumulators a given charging current after diobium before the voltage of the nickel-cadmium accumulators reaches a value of 1.45 V to 1.80 V, depending on the type of accumulators, the value of the capacity of the measured nickel-cadmium accumulators is then determined as the product .

This method is based on the existence of a direct relationship between the capacity value of the nickel-cadmium accumulators determined from the discharge curve after reaching a final discharge voltage of 1.0 V and the capacity value found when charging the accumulator to a steep part of the charging curve. charging, which is associated with a significant increase in voltage of 200 to 300 mV depending on the type of battery and its life.

The value of the capacity of the nickel-cadmium accumulators obtained from the charging curve corresponds to the values of the charging voltage, which ranges from 1.50 to 1.73 V and depends on the type of measured battery.

The method of experimentally determining the capacity of the nickel-cadmium accumulators from the charging curve according to the invention brings the following advantages for the users of these accumulators:

delivers significant electricity savings of 150% of each battery's rated capacity, reduces capacity testing by eliminating 1 discharge / charge cycle, and further ensures greater current stability and thus accuracy of the capacity test by eliminating current interruptions during the current process carrying out a capacity test due to the need to disconnect cells with a completed capacity test when measuring the entire battery system consisting of up to 50 pieces of series-connected accumulators.

To ensure the accuracy of the determination of the capacity of each type of nickel-cadmium accumulator shown in the examples below, an Ah-counter of its own design was used, allowing direct measurement of the delivered and withdrawn capacity of the measured accumulators in Ah.

Discharging of all evaluated nickel-cadmium accumulators was carried out with 0.2 Cs JA], since mainly users of KPH batteries (formerly NKS) cannot meet the existing CSN 36 4350 ST SEV using a discharge current of 1 Ci [A] due to significantly higher demands of the discharge process both in terms of the discharge current and in terms of the entire capacity test compared to the current 0.2 Cs [Al] discharge current used in the previously valid CSN.

Charging of these accumulators was carried out with both 0.2 Cs [A] and 0.25 Ci [A] current.

With respect to the generalization of the respective value of the charging voltage for determination of the capacity of the given type of nickel-cadmium accumulator, the value of the charging voltage was determined in a wide range of lifetime of these accumulators cycled according to the relevant CSNs as well as in operating conditions of their function.

Examples:

He did

Nickel-cadmium accumulators of type KPH 80 (formerly NKS 80) after various cycles according to CSN were subjected to equalization cycles by charging with 0.25 C4 [A] current and discharge with 0.2 Cs [A] current to a final voltage of 1.0 V These cycles were followed by the actual capacity test of the evaluated accumulators, ie charging with 0.2 Cs [A] for 7.5 hours, ie. 150% of nominal capacity. This was followed by discharging these batteries with a current of 0.2 Ci [A] to a final voltage of 1.0 V.

The corresponding charging curve for both types of charging modes are shown in Fig. 1 for one of the KPH 80 rated batteries.

Discharging capacities of evaluated accumulators together with (corresponding values of charging voltage are given in Table 1. Table 2 shows errors caused by measuring the capacity of evaluated accumulators in the current way used by their users when discharging up to 1.10 V together with the error. when determining the capacity of these accumulators using the method proposed by us to determine it from the charging curve.

Table 1 accumulator cycle acc. To CS charging current 0,2 Cs (A) type number-discharge capacity corresponding charging [Ah] voltage (V)

KPH 80 2 630 936 84.7 1.62 KPH 80 831 936 82.3 1.62 KPH 80 371 936 83.9 1.62 KPH 80 371 3 97.6 1.62 KPH 80 1112 3 98.4 1.62 KPH 80 1489 436 93.6 1.62 KPH 80 2 630 537 92.0 1.62 KPH 80 diameter - -. 1.62 Table 2 type measurement errors battery existing ways a new way and Bc % Cj charging 0.2 Cs (A) KPH 80 +12,5 —2.2 —5.0 +12,5 ± 1.3 / 0.01 V

- 7.2 a - Error caused by battery discharging up to 1.10 V b - Error caused by current instability c - Error caused by current interruption when discharging eg 50 accumulators due to gradual disconnection of cells with final discharge (time needed to disconnect 1 battery including discharge reconnection - 15 sec)

Example 2

Nickel-cadmium accumulators of type KPH 80 (formerly NKS 80) after different number of cycles according to CSN were subjected to equalization cycles during charging with 0.25 C4 [A] current and discharge with 0.2 Cs [A] current to the final voltage of 1.0 V These cycles were followed by the actual capacity test of evaluated accumulators, ie charging with 0.25 C4 [A] current for 6 hours, ie. 150 ° / o nominal capacity. This was followed by discharging these accumulators with a current of 0.2 Cs [A] to a final voltage of 1.0 V.

The respective charging and discharging curves for both types of charging modes are shown in Fig. 1 for one of the KPH 80 rated batteries.

The discharging capacities of the evaluated accumulators together with the corresponding values of the charging voltage are given in Table 3. Table 4 shows the errors arising from the measurement of the capacity of the evaluated accumulators used by their users when discharging up to 1.10 V together with the error determining the capacity of these accumulators using the method proposed by us to determine it from the charging curve.

Table 3 Battery CSN cycle

type number KPH 80 2 630 937 KPH 80 831 937 KPH 80 371. 937 KPH 80 371 3 KPH 80 1112 3 KPH 80 1489 436 KPH 80 2 630 537 KPH 80 diameter -

Charging current 0.25 C4 [A] discharge capacity corresponding to charging [Ah] voltage [V]

81.5 1.69 81.0 1.69 82.4 1.68 - - - - - - - -

Battery type

Table 4 measurement errors existing methods b c

2J [% Cj] new charging method 0.25 C4 [A]

KPH 80 +12.5 —2.2 —5.0 +12.5 + 2.1 / 0.01 V

- 7.2 a - error caused by discharging of batteries up to 1.10 V b - error caused by current instability c - error caused by interruption of current when discharging eg 50 batteries due to gradual disconnection of cells with discharged finished (time needed to disconnect 1 battery). including discharging - 15 sec)

Example 1 a d 3

Nickel-cadmium accumulators type KPM 160 (formerly NKT 160) after 2 to 5 years of operation in battery-powered trolleys were subjected to equalization cycles when discharging at 0.2 Cs [A] to a final discharge voltage of 1.0 v: After these cycles Charging at 0.2 Cs [A] for 7.5 hours, ie by supplying 150% of rated capacity. This was followed by discharging these accumulators with a current of 0.2 Cs [A] to a final voltage of 1.0 V.

The respective charging and discharging curves for both types of charging modes are shown in Fig. 2 for one of the KPM 160 batteries evaluated.

The discharging capacities of the evaluated accumulators together with the corresponding value of the charging voltage are given in Table 5. Table 6 shows the errors resulting from the measurement of evaluated accumulators by the current methods used for their users together with the error of determination of the capacity of these accumulators curves.

T a b u 1 k and no. 5 battery type number operating time charging current 0,2 Cs [A] discharge capacity corresponding charging [Ah] voltage [V]

KPM 160 29297 2 years 139.4 KPM 160 26540 2 years 142.6 KPM 160 32855 5 years 110.5 KPM 160 26355 3. cycle 173.9 KPM 160 24261 3. cycle 160.0 KPM 160 22559 3. cycle 164.3 KPM 160 28398 3. cycle 162.7 KPM 160 diameter

Table 6

1.67

1.68 1.68 1.65

1.65

1.66 1,68 1,67 battery type a

measurement errors existing methods b c

Σ [% Cj] new charging method 0.2 Cs [A]

KPM 160 +4.2 +0.8 —5.0 +5.0 + 1.9 / 0.01 {V] —5.0 a - error caused by battery discharge only up to 1.10 V b - error occurred current instability c - error caused by interruption of current when discharging eg 50 accumulators due to gradual disconnection of cells with finished discharge (time needed to disconnect 1 accumulator including reconnection of discharge - 15 sec).

Example 4

Nickel-cadmium accumulators type KPM 160 (formerly NKT 160) after 2 to 5 years of operation in battery-powered trolleys were subjected to equalization cycles when discharging at 0.2 Cs [A] to a final discharge voltage of 1.0 V. After these cycles the accumulators were subjected to Charging at 0.25 Cl [A] for 6 hours, ie by supplying 150% of the rated capacity, followed by a 0.2 Cs charge (Aj to 1.0 V final voltage).

The respective charging and discharging curves for both types of charging modes are shown in Fig. 2 for one of the KPM 160 batteries evaluated.

The discharging capacities of the evaluated accumulators together with the corresponding value of the charging voltage are given in Table 7. Table 8 lists errors resulting from the measurement of the evaluated accumulators by the current methods used for their users together with the error of determining the capacity of these accumulators curves.

Table 7 accumulator operating time charging current 0.25 C4 [A] type number discharge capacity corresponding charging [Ah] voltage [V]

KPM 160 29297 2 years 137.1 1.69 KPM 160 26540 2 years 142.6 1.70 KPM 160 32855 5 years 106.3 1.71 KPM 160 26355 3. cycle - - KPM 160 24261 3. cycle - - KPM 160 22559 3. cycle - - KPM 160 28398 3. cycle - - KPM 160 diameter 1.70

Battery type

Table 8 11 measurement errors existing ways Σ [% Cj] a new way Bc charging 0,25 C4 [A]

KPM160 +4.2 +0.8 —5.0 +5.0 + 1.78 / 0.10 V —5.0 a - error due to battery discharge up to 1.10 V b - error due to current instability c - error caused by power interruption when measuring 50 accumulators due to the gradual disconnection of cells with discharged end (time needed to disconnect 1 accumulator including re-connection of the discharge - 15 sec).

Example 5

Nickel-cadmium accumulators type KPL 118 (formerly NKO 118) after 3/4 years of operation as emergency sources of residential lighting were subjected to equalization cycles when charging with 0.25 Ci [A] current and 0.2 Cs [A] current discharge to the final After these cycles, the accumulators were subjected to a self-capacitance test, i.e. charged at 0.2 Cs [A] for 7.5 hours at 150% of rated capacity. This was followed by discharging these accumulators with a current of 0.2 Cs [A] to a final voltage of 1.0 V / accumulator.

The respective charging and discharging curves for both types of charging modes are shown in Fig. 3 for one of the KPL 118 rated batteries.

The discharging capacities of the evaluated accumulators together with the corresponding values of the charging voltages of all the measured accumulators are shown in Table 9. Table 10 lists the errors resulting from measuring the capacity of the evaluated accumulators by the current methods used by their users. of accumulators resulting from the use of our proposed method of its determination from the charging curve.

Table 9 accumulator charging current 0,2 Cs [A] type number discharge capacity [Ah] corresponding charging voltage [V] KPL 118 3515 114.4 1.69 KPL 118 3566 119.4 1.70 KPL 118 3604 123.8 1.71 KPL 118 diameter Table 10 1.70 type existing ways 2J [% Cj] new method battery measurement errors and Bc charging 0.2 Cs [A]

KPL 118 +3,4 —1,9 —5,0 +3,4 + 3,8 / 0,01 —6,9 a— error caused by battery discharge only up to 1.10 V b - error caused by current instability c - current interruption error when measuring 50 accumulators due to the gradual disconnection of cells with finished charging (time required to disconnect 1 accumulator including re-connection of discharge - 15 sec).

Example 6

Nickel-cadmium accumulators of type KPL 118 (formerly NKO 118) after 3/4 years of operation as emergency sources of residential lighting were subjected to equalization cycles when charging with a current of 0.25 C4 [A] and discharging with a current of 0.2 C5 [A] to the final After these cycles, the accumulators were subjected to their own capacitance test, ie charged at 0.25 Ch [A] for 6 hsdin, ie at 150% of rated capacity. This was followed by discharging these batteries with a current of 0.2 C5 [A] to a final voltage of 1.0 V.

The respective charging and discharging curves for both types of charging modes are shown in Fig. 3 for one of the KPL 118 rated batteries.

The discharging capacities of the accumulators together with the corresponding values of the charging voltages of all measured accumulators are given in Table 11. Table 12 shows the errors caused by measuring the capacity of evaluated accumulators by the current methods used by their users. using the method proposed by us to determine it from the charging curve.

accumulator Table 11 charging current 0.25 C4 [A] discharge capacity corresponding to charging type number [Ah] voltage [V] KPL 118 3515 111.5 1.74 KPL 118 3566 115.2 1.72 KPL 118 3604 117.7 1.73 KPL 118 diameter 1.73 Table 12 type measurement errors battery existing methods L [% Cj] a new way and Bc charging 0.25 Ci [Al KPL 118 +3,4 —1.9 —5.0 '+3.4 + 3.1 / 0.01 V

–6,9 a - error caused by battery discharging up to 1.10 V b - error caused by current instability c - error caused by current interruption when measuring 50 accumulators due to gradual disconnection of cells with finished discharge (time needed to disconnect 1 battery including reconnection) discharge - sec).

Example 7

Nickel-cadmium accumulators of the type KPL 60 (formerly NKN 60) after various cycles according to ČSN 36 4350 ST SEV were subjected to equalization cycles during charging with 0.25 Cd [Aj and discharge with 0.2 C5 [AJ] to the final discharge voltage 1, After these cycles, these batteries were subjected to a charge of 0.2 cs [A] for 7.5 hours, ie supplying 150% of the rated capacity. This was followed by discharging these batteries with a current of 0.2 C5 [A] to a final voltage of 1.0 V.

The respective charging and discharging curves for both types of charging modes are shown in Fig. 4 for one of the KPL 60 batteries evaluated.

The discharging capacities of the evaluated accumulators together with the corresponding value of the charging voltage are given in Table 13. Table 14 shows the errors resulting from measuring the capacity of the evaluated accumulators by the current methods used for their users. determination from the charging curve.

From these results it is clear that even after 1,440 cycles, ie three times higher lifetime of Ni-Cd accumulators of the KPL 60 type than required by the relevant CSN, the accumulators no longer meet the required nominal capacity according to CSN equal values of charging voltage corresponding to their capacity at discharge as early in life.

Table 13 accumulator cycle charge current 0.2 Č6 [A] type number discharge capacity corresponding charging [Ah] voltage [V]

KPL 60 15496 1440 a 1441 25.1 1.55 KPL 60 14612 1 440 a 1441 29.8 1.57 KPL 60 16177 1440 a 1441 36,9 1.56 KPL 60 15496 3 66.0 1.55 KPL 60 14612 3 61.2 1.57 KPL 60 16177 3 62.4 1.56 KPL 60 15496 593 56.8 1.55 KPL 60 14612 593 55.6 1.57 KPL 60 16177 593 53.6 1.57 KPL 60 diameter type battery T a b u 1 k and No. 14 measurement errors existing ways L [% C] 1.56 a new way and Bc charging 0.2 Cs [Aj KPL 60 +4.2 —0.7 —5.0 +4.2 + 1.0 / 0.01 [V] a - error b - error originated originated when the batteries are discharged up to 1.10 V only, with current instability -5.7 c - error originated by discharging the current when discharging eg 50 accumulators due to p>

step-by-step disconnection of the batteries with the discharge discharged (time required to disconnect 1 battery including re-connection of the discharge - 15 sec).

Example 8

Nickel-cadmium accumulators of the type KPL 60 (formerly NKN 60) after various cycles of charging at 0.25 Cl [A] and discharging at 0.2 Cs [A] to a final discharge voltage of 1.0 V. After these cycles, these the accumulators are charged at 0.2 Cs [A] for 6 hours, ie by supplying 150% of the nominal capacity. This was followed by discharging these accumulators with a current of 0.2 Cs [Aj] to a final voltage of 1.0 V.

The respective charging and discharging curves for both types of charging modes are shown in Figure 4 for one of the KPL 60 batteries evaluated.

The discharging capacities of the evaluated accumulators together with the corresponding value of the charging voltage are given in Table 15. Table 16 lists errors resulting from the measurement of the capacity of the evaluated accumulators by the current methods used for their users. determination from the charging curve.

It is clear from these results that even after 1,440 cycles, ie three times higher lifetime of KPL 60 type Ni-Cd accumulators than required by ČSN, these accumulators, which no longer meet the required nominal capacity according to ČSN, achieve the same values of charging voltage corresponding to their discharge capacity as early in life.

battery type number

Table 15 Cycle charging current 0.25 Ci [Al capacitance at discharge corresponding to charging [Ah] voltage [VJ

KPL 60 15496 1440 and 1441 24.8 1.58 KPL 60 14612 1440 and 1441 29.5 1.60 KPL 60 16177 1440 and 1441 36.4 1.59 KPL 60 15496 3 - - KPL 60 14612 3 - - KPL 60 16177 3 - - KPL 60 15496 593 - - KPL 60 14612 593 - - KPL 60 16177 593 - - KPL 60 diameter 1.59

T a b u 1 k and No. 16 type battery and measurement errors existing ways Bc £ [% Cjj new charging method 0,25 C4 [A] KPL 60 +4.2 —0.7 —5.0 +4.2 + 0.7 / 0.01 V

a - error caused by discharging of batteries pause up to 1.10 V b - error caused by current instability c - error caused by interruption of current when discharging eg 50 batteries due to gradual disconnection of cells with finished discharge 15 sec].

The method of determining the capacity of Ni-Cd accumulators according to said patent can be used to determine the capacity of Ni-Cd accumulators for a number of users, such as railway repair and engine rooms, mechanism repair workshops and individual railway stations in railway transport urban transport, individual plants with in-house transport, local economy enterprises and others.

Claims (1)

SUBJECT Method for experimentally determining the capacity of nickel-cadmium accumulators with pocket electrodes, characterized by first discharging nickel-cadmium accumulators to a voltage of 1.0 V, followed by charging the measured accumulators with a given charging current for a time before the voltage OF THE INVENTION The nickel-cadmium accumulators reach a value of 1.45 V to 1.80 V, depending on the type of accumulators, and the value of the capacity of the measured nickel-cadmium accumulators is then determined as the product of the determined time and current with which the accumulator is charged. 4 sheets of drawings