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Basic requirements for batteries and battery packs for explosion-proof electrical equipment

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| 2022-02-28|Return

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 atmospheres - Part 2: Equipment protected by explosion-proof enclosures" d ".

Appendix E


Batteries used inside explosion-proof enclosures

E. Lsummary

This appendix contains the requirements for batteries or battery packs that provide power to circuits within equipment protected by explosion-proof enclosures.

Regardless of the type of electrochemical battery used, consideration should be given to preventing the formation of flammable mixtures of electrolytic gases (usually hydrogen and oxygen) inside the explosion-proof enclosure. Considering this, batteries that may release electrolytic gas (through natural exhaust holes or through pressure relief valves) during normal use should not be used inside explosion-proof enclosures.

Note: These requirements do not apply to electrochemical batteries used in measuring devices (such as A-type zinc/oxygen batteries specified in GB/T 8897.1 for measuring oxygen concentration).

E. 2Permissible electrochemical systems

Only batteries that meet the battery standards in Tables E.1 and 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 they can only be used for discharge purposes;

——When meeting the requirements of E.5, airtight batteries can be charged inside an explosion-proof enclosure.

E. 3.2The explosion-proof shell containing the battery should be marked with the markings specified in item d) of Table 14

When the battery and its connected circuit meet the requirements of GB/T 3836.4 and the battery is not charging during operation, this requirement does not apply

E. 3.3The battery pack and its associated safety devices 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 the relevant explosion-proof type 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. 4Layout of safety devices

E. 4.1Prevent high temperature and battery damage

E. 4.1.1Under short-circuit discharge conditions, the battery shall either meet the following conditions or install safety devices as required by E.4.1.2:

A)Considering the local environmental 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. The safety device should comply with the provisions of GB/T 3836.4 for reliable components with a "ib" protection level, be installed as close as possible to the battery's wiring terminals, and should 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 fusing performance that can prevent exceeding the manufacturer's specified maximum discharge current and allowable duration. If the fuse is a replaceable model, a label should be placed next to the fuse holder to indicate the type and parameters of the fuse used.

The rated value of resistors or current limiters should be based on the voltage of the battery or battery pack.

E. 4.2Prevent battery polarity reversal 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 specified values, its arrangement should prevent polarity reversal or reverse charging by another battery within the same battery pack.

Here are two examples of how to meet this requirement:

- Monitor the voltage at both ends of individual batteries (or several individual batteries), and cut off the power 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 series connected batteries, it may sometimes lose its effectiveness due to voltage errors of individual batteries and protection circuit reasons. Monitoring more than 6 (series) batteries with one protection device is ineffective.

——Use bypass diodes to limit the voltage of each individual battery when its polarity is reversed. For example, the protection circuit provided by a battery pack consisting of three individual batteries connected in series is shown in Figure E.1.

To provide effective protection for this protection circuit, the voltage drop of the diode that prevents reverse charging of each battery 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 hour), 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 is another power source (including other batteries) inside the same casing, the battery and its associated circuits should be protected from being charged by other circuits. For example:

——Isolate the battery, its associated circuits, and other power sources inside the casing using the electrical clearance and creepage distance specified in GB/T 3836.3 for the highest voltage that can cause pollution; 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 circuit protection provided, such as fuses, ground fault protection); or

——Using the electrical clearance and creepage distance specified in GB/T 3836.3 only isolates the battery from other power sources, but installing a blocking diode as shown in Figure E.2 can reduce the risk of a single fault caused by a short circuit between two diodes.

E. 4.3The requirements in the example do not apply to circuits that establish voltage reference points connected to batteries or to charging power circuits for batteries that meet the requirements of E.5.

E. 5Charging the battery inside the explosion-proof housing

E. 5.1Only the batteries listed in Table E.2 can be charged inside explosion-proof enclosures.

E. 5.2When a single battery or battery pack is charged inside an explosion-proof 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 limit the use of single cell batteries (or battery packs) without safety devices installed, such as those commonly referred to as "button type single cell batteries" used to maintain memory on programmable electronic circuits inside explosion-proof enclosures.

E. 5.5If the battery capacity and/or volume exceed the specified values, and the battery is equipped with safety devices, the charging current can be cut off when the voltage of any individual battery in the battery pack exceeds the manufacturer's maximum voltage, and the production and possible release of electrolytic gas can be prevented before the battery is allowed to charge inside the explosion-proof enclosure.

E. 6Rating of protective diodes and 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 in 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 current rating 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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