Battery is one of the main power supply methods for explosion-proof electrical equipment, and it is also a technical difficulty that customers often encounter during the explosion-proof testing and certification process of their products. hereZhongnuo TestingShare the basic requirements for batteries and battery packs of explosion-proof electrical equipment in GB/T 3836.2-2021 "Explosive Atmosphere Part 2: Equipment Protected by Flameproof Enclosures".
Appendix E
(Normative)
Batteries used inside explosion-proof enclosures
E.lsummary
This appendix contains requirements for batteries or battery packs that provide power to circuits within equipment protected by explosion-proof enclosures "d".
Regardless of the type of electrochemical cell used, consideration should be given to preventing the formation of flammable mixtures of electrolytic gases (usually hydrogen and oxygen) within the explosion-proof enclosure. Considering this, batteries that may release electrolytic gas during normal use (through natural exhaust vents or pressure relief valves) should not be used inside explosion-proof enclosures.
Note: These requirements do not apply to electrochemical cells used in measuring devices (such as A-type zinc/oxygen cells specified in GB/T 8897.1 for measuring oxygen concentration).
E.2Permitted electrochemical systems
Only batteries that meet the battery standards in Table E.1 and Table E.2 should be used.
E.3General requirements for batteries (or battery packs) inside explosion-proof enclosures
E.3. 1The following usage restrictions should apply to certain types of batteries:
——Exhaust or open type batteries should not be used to form battery packs inside explosion-proof enclosures;
——Valve controlled sealed batteries can be used inside explosion-proof enclosures, but can only be used for discharge purposes;
——When meeting the requirements of E.5, airtight batteries can be charged inside explosion-proof enclosures.
E.3.2The explosion-proof casing containing batteries should be marked with the symbol specified in item d) of Table 14
When the battery and the circuit connected to it meet the requirements of GB/T 3836.4 and the battery does not charge during operation, this requirement does not apply
E.3.3The battery pack and the safety devices connected to it should be securely installed (such as clips or brackets designed for this purpose).
E.3.4There should be no relative displacement between the battery and the safety device connected to it, otherwise it will hinder compliance with relevant explosion-proof requirements.
E.3.5According to the requirements of GB/T3836.1, it should be checked whether it meets the requirements of E.3.3 and E.3.4 before and after the shell test.
E.4Arrangement of safety devices
E.4.1Prevent excessive temperature and battery damage
E.4.1.1Under short-circuit discharge conditions, the battery either meets the following conditions or is equipped with safety devices as required by E.4.1.2:
a)Considering the local ambient temperature inside the casing, the outer surface temperature of the battery should not exceed the continuous operating temperature specified by the battery manufacturer; and
b)The maximum discharge current should not exceed the value specified by the battery manufacturer.
E.4.1.2When the two conditions of E.4.1.1 cannot be met, a safety device is required, which should comply with the provisions of GB/T 3836.4 for "ib" protection level reliable components, be installed as close as possible to the battery terminal, and be one of the following:
——Resistors or current limiters that limit the current to not exceed the maximum continuous discharge current specified by the battery manufacturer;
——Fuses that meet the requirements of GB/T 9364 (all parts) have a melting performance that prevents exceeding the maximum discharge current and allowable duration specified by the manufacturer. If the fuse is a replaceable model, a label should be placed next to the fuse holder to indicate the fuse model and parameters used.
The rated value of resistors or current limiters should be based on the voltage of the battery or battery pack.
E.4.2Prevent reverse polarity of the battery or reverse charging by other batteries within the same battery pack
E.4.2. 1If the battery used has:
a)Capacity not exceeding 1.5Ah (at a discharge rate of 1h), and
b)The volume is less than 1% of the net volume of the shell,
There is no need to provide additional protection against the release of electrolytic gas due to polarity reversal or reverse charging by other batteries within the same battery pack.
E.4.2.2If the capacity and/or volume of the battery exceeds the above specified values, its arrangement should prevent polarity reversal or reverse charging by another battery in the same battery pack.
Here are two examples of how to meet this requirement:
- Monitor the voltage across a single battery (or several individual batteries) and cut off the power supply when the voltage drops below the minimum voltage specified by the battery manufacturer;
Note 1: This type of protection is often used to prevent batteries from entering a "deep discharge" state. If the protection device monitors too many batteries connected in series, it may sometimes lose its effectiveness due to voltage errors in a single battery and protection circuit reasons. Monitoring more than 6 (series) batteries with one protection device is ineffective.
——Use bypass diodes to limit the voltage when the polarity of each individual battery is reversed. For example, the protection circuit provided by a battery pack consisting of three individual cells connected in series is shown in Figure E.1.
In order for this protection circuit to provide effective protection and prevent the voltage drop of the diode for reverse charging of each battery, it should not exceed the safe reverse charging voltage of the individual battery.
Note 2: Silicon diodes are considered to meet this requirement.
E.4.3Prevent charging the battery from another power source inside the casing
If the battery used has:
——Capacity not exceeding 1.5 Ah (at a discharge rate of 1 h), and
——The volume is less than 1% of the net volume of the shell,
There is no need to use additional protection for the battery to prevent the release of electrolytic gas during charging.
When there are other power sources (including other batteries) inside the same enclosure, the battery and its associated circuits should be protected from being charged by other circuits. For example:
——Using the electrical clearance and creepage distance specified in GB/T 3836.3 for the highest voltage that can cause pollution inside the casing to isolate the battery and its associated circuits from other power sources; or
Using a grounded metal barrier/shield inside the casing to isolate the battery and its associated circuits from other power sources, the barrier/shield can withstand the maximum fault current of the power source during the time when fault current may exist (considering the provided circuit protection, such as fuses and ground fault protection); or
——The electrical clearance and creepage distance specified in GB/T 3836.3 are only used to isolate the battery from other power sources, but a blocking diode as shown in Figure E.2 is installed to reduce the risk of a single fault caused by a short circuit between two diodes.
E.4.3The requirements of the example do not apply to circuits that establish voltage reference points connected to batteries or power supply circuits that charge batteries that meet the requirements of E.5.
E.5Charging the battery inside the explosion-proof shell
E.5.1Only the batteries listed in Table E.2 can be charged inside the explosion-proof enclosure.
E.5.2When a single battery or battery pack is charged inside a flameproof enclosure, the manufacturer's documentation should specify detailed charging conditions and safety devices should be used to ensure that these conditions are not exceeded.
E.5.3The charging device should prevent reverse charging.
E.5.4If the battery used has:
——Capacity not exceeding 1.5 Ah, and
——The volume is less than 1% of the net volume of the shell,
There is no need to use additional safety devices on the battery to prevent the release of electrolytic gas during charging.
Note: The above requirements effectively restrict the use of single cells (or battery packs) without safety devices installed, such as those commonly referred to as "button type single cells" used to maintain memory on programmable electronic circuits inside explosion-proof enclosures.
E.5.5In the case where the battery capacity and/or volume exceed the above specified values, if the battery is equipped with a safety device that can cut off the charging current when the voltage of any individual battery in the battery pack exceeds the maximum voltage specified by the manufacturer, and prevent the generation and possible release of electrolytic gas, the battery is allowed to be charged inside the explosion-proof shell.
E.6The rating of protective diodes and the reliability of protective devices
E.6.1The voltage rating of the installed protective diode that meets the requirements of E.4.2 should not be less than the maximum open circuit voltage of the battery.
E.6.2The voltage rating of the series connected blocking diode installed inside the explosion-proof enclosure that meets the requirements of E.4.3 should not be less than the highest peak voltage inside the explosion-proof enclosure.
E.6.3The rated current of the protective diode should not be less than the maximum discharge current limited in E.4.1.
E.6.4The safety devices required in this document constitute the safety components related to the control system. It is the responsibility of the manufacturer to evaluate the complete safety performance of the control system to meet the safety level specified in this document.
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