Primary batteriesPart 3: Watch batteries BSI Standards Publication... The following dates are fixed: • latest date by which the document has to be implemented at national level by public
Battery dimensions, symbols and size codes
Dimensions and tolerances of batteries for watches shall be in accordance with Figure 1, Table 1 and Table 2 The dimensions of the batteries shall be tested in accordance with 7.1
The symbols used to denote the various dimensions in Figure 1 are in accordance with IEC 60086-2:2015, Clause 4
The overall height of the battery must not exceed the specified maximum (h1), while the minimum distance between the positive and negative contact flats (h2) is crucial for safety Additionally, the flat negative contact must have a minimum projection (h5) to ensure proper functionality The battery's diameter is defined by both maximum and minimum limits (d1), and the flat positive contact must meet a minimum diameter requirement (d2), as well as the flat negative contact (d4).
NOTE This numbering follows the harmonization in the IEC 60086 series
Table 1 – Dimensions and size codes D im en sio ns in m ill im et re s D iam et er d 4
H ei ght h 1 / h 2 C ode a d 1 Tol e- ra nc e
The tolerance values for various codes are specified as follows: Code 10 has a tolerance of 0 – 0.10, while Code 12 has a tolerance of 0 – 0.25 Codes 14, 16, and 20 also have tolerances of 0 – 0.15, 0 – 0.18, and 0 – 0.20, respectively Codes 21 through 27 maintain a tolerance of 0 – 0.20, and Codes 30 to 32 have tolerances ranging from 0 – 0.25 to 0 – 0.30 Notably, open boxes in the matrix may not be available for standardization due to overlapping tolerances, as referenced in Annex A.
Table 2 – Dimensions and size codes
NOTE Open boxes in the above matrix are not necessarily available for standardisation due to the concept of overlapping tolerances a See Annex A.
Terminals
Negative contact (–): the negative contact (dimension d 4 ) shall be in accordance with
Tables 1 and 2 This is not applied to those batteries with a two-step negative contact
Positive contact (+): the cylindrical surface is connected to the positive terminal Positive contact should be made to the side of the battery but may be made to the base.
Projection of the negative terminal (h 5)
The dimension h 5 shall be as follows: h 5 ≥ 0,02 for h 1 /h 2 ≤ 1,65 h 5 ≥ 0,06 for 1,65 < h 1 /h 2 < 2,5 h 5 ≥ 0,08 for h 1 /h 2 ≥ 2,5
The negative contact should be the highest point of the battery.
Shape of negative terminal
The space requirements shall be contained within an angle of 45° (see Figure 2)
The minimum values of l 1 , for different heights of h 1 /h 2 , are given in Table 3
Figure 2 – Shape of negative terminal Table 3 – Minimum values of l 1
Mechanical resistance to pressure
A force F (N), detailed in Table 4, applied for 10 seconds via a 1 mm diameter steel ball at the center of each contact area, must not result in any deformation that could impair the battery's functionality Following this test, the battery is required to successfully pass the specified tests.
Table 4 – Applied force F by battery dimensions
Battery dimensions Force d 1 h 1 /h 2 F mm mm N
Deformation
The dimensions of batteries shall conform with the relevant specified dimensions at all times including discharge to the defined end-point voltage
NOTE 1 A battery height increase up to 0,25 mm can occur, if discharged below this voltage
NOTE 2 A battery height decrease can occur in B and C systems as discharge continues.
Leakage
Undischarged batteries and, if required, batteries tested according to 7.2.6 shall be examined as stated in 7.3 The acceptable number of defects shall be agreed between the manufacturer and the purchaser
Marking
General
Battery markings must clearly indicate the designation and polarity without obstructing electrical contact Additional information, such as the designation per normative Annex A or common standards, and the expiration date or manufacturing date (year and month or week), can be placed on the packaging instead of the battery itself The manufacturing date may be encoded, using the last digit of the year and a number for the month, with October, November, and December represented by the letters O, Y, and Z, respectively.
In November 2014, important specifications for batteries were outlined, including the polarity of the positive (+) terminal, nominal voltage, and the supplier's name or trademark Additionally, cautionary advice regarding battery safety and warnings against ingestion must be provided For detailed guidelines, refer to IEC 60086-4:2014 (sections 7.2 a and 9.2) and IEC 60086-5:-1 (sections 7.1 l and 9.2).
NOTE Examples of the common designations can be found in Annex D of IEC 60086-2:2015.
Disposal
Marking of batteries with respect to the method of disposal shall be in accordance with local legal requirements
Electrochemical system, nominal voltage, end-point voltage and open-circuit
The requirements concerning the electrochemical system, the nominal voltage, the end-point voltage and the open-circuit voltage are given in Table 5
Letter Negative electrode Electrolyte Positive electrode Nominal voltage End- point voltage
B Lithium (Li) Organic electrolyte Carbon monofluoride (CF) x 3,0 2,0 3,70 3,00
C Lithium (Li) Organic electrolyte Manganese dioxide (MnO 2 ) 3,0 2,0 3,70 3,00
L Zinc (Zn) Alkali metal hydroxide Manganese dioxide (MnO 2 ) 1,5 1,0 1,68 1,50
S Zinc (Zn) Alkali metal hydroxide Silver oxide (Ag 2 O) 1,55 1,2 1,63 1,57
Closed circuit voltage U cc (CCV), internal resistance and impedance
Closed circuit voltage and internal resistance shall be measured according to 7.2
AC impedance should be measured with an LCR meter
Limit values shall be agreed between the manufacturer and the purchaser.
Capacity
The capacity shall be agreed between the manufacturer and the purchaser on the basis of a continuous discharge test lasting approximately 30 days, according to 7.2.6.
Capacity retention
Capacity retention refers to the ratio of capacities measured under specific discharge conditions between fresh batteries and a sample from the same lot that has been stored for 365 days at a temperature of (20 ± 2) °C and a relative humidity of 55 ± 20%.
The ratio of capacity retention shall be agreed between the manufacturer and the purchaser
The minimum value should be at least 90 % for a period of 12 months The capacity measurement is carried out according to 7.2.6
For the purpose of verifying compliance with this standard, conditional acceptance may be given after completion of the initial capacity tests
The use of sampling plans or product quality indices should be agreed between manufacturer and purchaser
Where no agreement is specified, refer to ISO 2859 and ISO 21747 for sampling and quality compliance assessment advice
Shape and dimensions
Shape requirement
The shape of the negative contact is checked preferably by optical projection or by an open gauge according to Figure 3
The measurement method shall be agreed between the manufacturer and the purchaser
Electrical characteristics
Environmental conditions
Unless otherwise specified, the sample batteries shall be tested at a temperature of
During use, batteries may be exposed to low temperatures; it is therefore recommended to carry out complementary tests at (0 ± 2) °C and at (–10 ± 2) °C.
Equivalent circuit – effective internal resistance – DC method
The resistance of an electrical component is calculated by determining the ratio of the voltage drop (\( \Delta U \)) across the component to the current (\( \Delta i \)) flowing through it, expressed by the formula \( R = \frac{\Delta U}{\Delta i} \).
NOTE As an analogy, the internal d.c resistance R i of any electrochemical cell is defined by the following relation:
The internal d.c resistance is illustrated by the schematic voltage transient as given below in Figure 4
As can be seen from the diagram in Figure 4, the voltage drop ∆U of the two components differs in nature, as shown in the following relation:
The first component ∆U Ω for (t = t 1) is independent of time (ohmic drop), and results from the increase in current ∆i according to the relation:
In this relation, R Ω is a pure ohmic resistance The second component ∆U (t) is time dependent and is of electrochemical origin (capacitive reactance).
Equipment
The equipment used for the voltage measurements shall have the following specifications:
In the following tests, it is crucial to ensure that measurements are taken during the flat period of the voltage transient, as shown in Figure 5 Failing to do so may result in measurement errors caused by capacitive reactance, which can lead to lower internal resistance.
The time ∆t' necessary for the measurement shall be brief in comparison to ∆t, and the measurement equipment compatible with these criteria
1 open-circuit voltage U oc (OCV)
3 closed circuit voltage U cc (CCV)
Measurement of open-circuit voltage U oc (OCV) and closed circuit
First measurement U oc: The switch is left open while this measurement is being carried out
Next measurement U cc : The battery being tested shall be connected to the load R m The switch shall be left closed during the duration ∆t according to Table 6
Figure 6 – Circuitry principle Table 6 – Test method for U cc (CCV) measurement
Test method Battery with KOH electrolyte a All other batteries
When testing a battery, it is essential to account for the resistance of the connection lines and the contact resistance of the switch For applications with high peak current, Method A is recommended, as it requires specialized test equipment In cases where Method A equipment is unavailable, Method B can be utilized Method C should only be employed with mutual agreement between the manufacturer and the purchaser.
Calculation of the internal resistance R i
The internal resistance may be determined by the following calculation: m cc cc i U oc /R
NOTE The relation U cc / R m corresponds to the current delivered through the discharge resistance R m (see 7.2.4).
Measurement of the capacity
There are two methods for measuring capacity:
– the recommended method is method A, which is more indicative of watch requirements; – method B is a more general method and is already specified in IEC 60086-1 and IEC 60086-2
When presenting capacity data, the manufacturer shall specify which test method was used
7.2.6.2 Method A a) Circuitry principle (see Figure 7)
Figure 7 – Circuitry principle for method A b) Procedure
The duration of the discharge test at the resistor R d approximates to 30 days
The resistance value \( R_d \) of the resistive load, as detailed in Tables 7 and 8, must encompass all components of the external circuit and maintain an accuracy of ±0.5% Additionally, the capacity determination is essential for precise measurements.
The measurements of the open-circuit voltage U' oc and that of the closed circuit voltage
U cc tests are conducted daily on the battery connected to R d until the U cc value falls below the endpoint voltage specified in Table 5.
1) First measurement U' oc : the resistance R d being much higher than R m , U' oc approximates to U oc
The switch is left open while the measurement is being carried out
2) Next measurement U cc : the battery being tested is connected to R m The switch is left closed during the duration ∆t according to Table 7
Table 7 – Test method A for U cc (CCV) measurement
Batteries with KOH electrolyte All other batteries
3) Calculation of the capacity C: the capacity of the battery is obtained by adding the partial capacity amounts C p , calculated after each measurement with the following formula: d i p oc R t
C U′ × where t i is the time between two measurements
4) Near the end of discharge, it is recommended to carry out several measurements a day in order to obtain sufficient accuracy
7.2.6.3 Method B a) Circuitry principle (see Figure 8)
The circuitry principle for method B is illustrated in Figure 8 For detailed procedures, refer to section 7.2.6.2 b) The capacity determination occurs when the on-load voltage of the tested battery first falls below the specified endpoint outlined in Table 5, at which point the time \( t \) is calculated and defined as the service life.
The capacity is calculated by the following formula:
U cc (average) is the average voltage value of U cc during discharge duration time (0-t); t is the service life.
Calculation of the internal resistance R i during discharge in case of
After measuring U' oc and U cc as outlined in section 7.2.6, the internal resistance R i of the battery can be calculated using the formula: \$ R_i = \frac{m_{cc}}{U_{cc} - U'_{oc}} \$
Code number according to the dimensions
Code number according to the dimensions
NOTE Blank values under consideration.
Test methods for determining the resistance to leakage
Preconditioning and initial visual examination
Before carrying out the tests specified in 7.3.2 and 7.3.3, the batteries shall be submitted to a visual examination according to the requirements stated in Clause 8
For tests in 7.3.2.1 and 7.3.2.2, batteries shall be pre-stored at the specified temperature
Batteries must be transferred from the preconditioning chamber to the high temperature and humidity test chamber within minutes to prevent cooling and minimize the risk of condensation at elevated humidity levels The testing is conducted at temperatures of 40 °C and 45 °C for a duration of 2 hours.
High temperature and humidity test
The battery shall be stored under the conditions specified in Table 9
Table 9 – Storage conditions for the recommended test
Temperature Relative humidity Test time °C % days
The test time of 30 days may be used for an accelerated routine quality control test, whereas the test time of
90 days applies to qualification testing of new batteries
After agreement between the manufacturer and purchaser, the following testing conditions may be chosen (see Table 10)
Table 10 – Storage conditions for optional test
Temperature Relative humidity Test time °C % days
The test time of 20 days may be used for an accelerated routine quality control test, whereas the test time of
60 days applies to qualification testing of new batteries.
Test by temperature cycles
The battery shall be submitted to 150 temperature cycles according to the schedule in Figure 9:
Figure 9 – Test by temperature cycles
8 Visual examination and acceptance conditions
Preconditioning
Batteries must be stored for a minimum of 24 hours at room temperature and a relative humidity of 55 ± 20% before conducting the initial visual examination or after the tests outlined in Clause 7.
After the crystallization of the electrolyte, it is essential to monitor for any leakage If needed, the storage period can be extended beyond 24 hours This assessment is applicable to both new and used batteries, as well as those that have undergone various tests.
Magnification
The visual examination shall be carried out at a magnification of x15.
Lighting
The visual examination shall be carried out under a diffuse white light of 900 lx to 1 100 lx at the surface of the battery to be inspected.
Leakage levels and classification
The visual examination shall be carried out under a diffuse white light of 900 lx to 1 100 lx at the surface of the battery to be inspected (See Table 11)
Table 11 – Leakage levels and classification (1 of 2)
Minor salting was observed near the gasket, impacting less than 10% of its perimeter, as detected under a magnification of x15 The leak remains undetectable to the naked eye.
Visible traces of salting can be observed near the gasket, and at a magnification of x15, it is evident that these salts impact over 10% of the gasket's perimeter.
Salt spreads on both sides of the gasket can be detected with the naked eye, but do not reach the flat of the negative contact
Leaks can occur in clouds on either side of the gasket, reaching the edges of the flat negative contact but not extending to the central area of the flat negative contact.
C2 Leaks spread in clouds, which reach the central part of the flat negative contact
IEC IEC IEC IEC IEC
The accumulation of crystallised liquid coming from the electrolyte swells up on part of the cloud spread, which covers the entire surface of the flat negative contact
The accumulation of crystallised liquid coming from the electrolyte swells up on the entire cloud spread, which covers the entire surface of the flat negative contact
Acceptance conditions
The acceptable level, as well as the proportion of defective pieces, shall be agreed between the manufacturer and the purchaser
Fresh batteries, with a level of leakage exceeding S1, shall not be submitted for qualification
The acceptance criteria may be less restrictive for batteries which have been tested according to 7.3.2 If necessary, photographic references may be established
Watch batteries designed to meet specific standards are labeled with a system of coded letters and numbers Notably, the letter W signifies compliance with IEC 60086-3.
Electrochemical system letter according to Table 5
Round cell: (according to IEC 60086-1)
Dimension: height in tenths of millimetres
Letter P may be left out in the case of electrochemical system letter S
IEC 60068-2-78:2001, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady state
ISO 8601:2004, Data elements and interchange formats – Information interchange –
Representation of dates and times
ISO 2859, Sampling procedures for inspection by attributes package
ISO 21747, Statistical methods – Process performance and capability statistics for measured quality characteristics