Can Unapproved Batteries Be Used in Intrinsic Safe Circuits?

When designing new products, all the components used should ideally be already pre-approved.  But does that mean that if one or more of the components is not, the product will automatically be non-compliant with its applicable safety requirements?

As a Certification Body, we sometimes come across Intrinsic Safe circuits that are using unapproved batteries and the common question we get from the manufacturer is:  will this cause a problem when it comes to testing?

The good news is, if the batteries are not pre-approved components, they can still be tested and accepted based on the following testing requirements:

1. General Testing: Testing of batteries and/or cells to ensure in case of short circuit or reverse charging they will not explode.

Note: Cells used in Batteries that meet requirements of UL1642 or IEC 62133 battery standards are sufficient to meet this requirement

2. Electrolyte Leakage Test for Cells and Batteries: 10 samples of the battery are put through the worst-case scenario from one of the below:

• Short circuit until discharged (this is skipped if the level of protection is “ic” or Zone 2/22 or Category 3)
• Input/charging current, applied within the manufacturer’s recommendations
• Battery is charged, as per manufacturer’s recommendations, with one fully discharged cell or experiencing polarity reversal

Samples are then kept on blotting paper for 12 hours and if there is no electrolyte leakage from the samples, the test is considered a “pass”.

Note: If this test was conducted on rechargeable batteries, they shall be put through fully charged and discharged cycle at least twice. Also, if batteries are encapsulated in the product, they can be tested with encapsulation for leakage test.

3. Spark Ignition & Thermal Ignition Testing: Batteries and/or cells can be either evaluated for spark assessment or tested with spark ignition tester. For Thermal Ignition, they shall be tested for surface temperature requirements with both normal and abnormal conditions for “ia” and “ib”. For “ic”, it is only tested in normal conditions.

So, although using pre-approved components, when designing your Intrinsic Safe circuit, is always the best way to go, there is no need to despair if they’re not already approved. At the end of the day, the key goal is for your system to meet the applicable safety requirements for the intended market and if needed, the goal can still be achieved with just a few additional tests.

For questions about Intrinsic Safety or other Hazardous Locations equipment requirements, please contact LabTest Certification at info@labtestcert.com.