Battery Safety Testing 101 For Buyers + Videos

Batteries are an integral component for many of today’s electronics, so battery safety testing should be a key concern for importers.

Don’t forget that, as the importer of either batteries or electronic devices that include batteries, you’re liable for consumer injury should the batteries turn out to be dangerous. You should also assure that your batteries comply with your market’s regulatory demands, which could mean, for instance, not importing batteries made with certain materials.

So, how to assess whether your batteries will be compliant and safe? Battery safety testing.

Are batteries unsafe?

Any battery has the potential to be unsafe, although the degree that things can go wrong does vary a lot between the different types of batteries.

For instance, a primary cell leaking some alkaline solution and a lithium-ion battery that catches fire represent different levels of threats.

So, while all batteries need to be tested, it’s secondary rechargeable cells, such as the Li-ion batteries that are integrated into devices, that will generally need to be on the radar of electronics importers, rather than disposable primary cells (unless you specifically import these or include a set of them with your device), because they contain Lithium ions and highly-flammable electrolyte.

Since Li-ion batteries are fairly ubiquitous in today’s devices, be they cell phones, laptops, IoT devices, and even electric vehicles, let’s look at some of the high-profile safety issues caused by them in recent years:

• Boeing 787 Dreamliner Li-ion battery issues ground planes – until issues were solved, a number of airlines’ planes suffered from overheating batteries which could have been very dangerous.
• The infamous Samsung Galaxy Note 7 – the one cell phone everyone remembers for all the wrong reasons. Some phones exploded and forced a recall of 2.5 million units.
• The Hyundai Kona EV has just been recalled globally (late 2020) due to a fire risk from its Li-ion battery cells – 77,000 vehicles were affected.
• BMW has also recalled thousands of PHEVs in late 2020 due to battery cells with debris inside of them which could cause fire.
• Lithium-ion batteries purchased from Amazon have also exploded in the past.

This doesn’t mean that all Li-ion batteries are unsafe, far from it, but it does mean that, as the importer, you need to take all possible precautions to assure that the batteries are as safe for use as possible because if they fail they pose a fire risk. And that means battery safety testing.

How testing batteries benefits importers

There are 3 reasons to test batteries:

1. To confirm that they’re safe for consumers (or, in a B2B setting, for use in the field)
2. For assessing that their quality reaches your requirements
3. Monitoring your Chinese battery suppliers and assuring that they provide the batteries you have ordered, every single time 

Related 👉 If you’re an American importer, read this whitepaper: Lithium battery safety guidelines for shipping to the US

Don’t battery suppliers test their batteries before selling them?

Yes, they will usually run some basic tests on all of the batteries that they sell, such as charge-discharge cycle tests, but, as we discussed in this episode of our podcast about factory testing equipment (at 15:21 to be precise), they probably will not conduct as thorough a selection of tests as is necessary to assure safety unless contracted to. So this leaves you to take care of safety testing regardless of whether your supplier provides you with a test report (that’s a good thing, but shouldn’t overrule you running your own tests).

The supplier should be able to provide you with an authentic battery specification sheet and battery MSDS. These are good documents for you to have in hand for comparison with your quality plan and lab test results, and they speak to the credibility of the supplier, too.

What battery safety testing do you need to conduct?

When testing battery safety and performance, we suggest performing the following tests, as a minimum:

• Test lifetime in the product (force charge-discharge with max usage)
• Test battery performance in different temperatures (temperature cycle testing)
  
• Measure battery self-discharge
• Other reliability/safety tests advised by professionals on your specific product
• Test to the UN38.3 standard for safe shipping

Battery lifetime test (force charge-discharge with max usage & temperature cycle testing)

This type of cycle testing will help you to assess the battery’s lifetime by measuring how many times it can be used and reused before it deteriorates to the point where it is no longer able to fulfil the power requirements of the device it is powering. This is usually pegged at around when the battery’s nominal capacity falls to less than 80% of its full capacity when new.

Banks of cells (7 recommended as a minimum) are rapidly charged and discharged an average of 20 times using the manufacturer’s specified voltage and charge/discharge limits in order to assess whether their claims on lifetime are correct. If the batteries prove not to provide the correct life cycle, then the buyer may experience costly warranty claims as the batteries will not live up to consumer expectations during the warranty period.

The temperature that the batteries are tested at and the depth of discharge will usually be regulated for the tests, although in some cases they may vary of this provides a more realistic set of results.

It is not recommended to overcharge or over-discharge the cells, as this will negatively affect the lifetime of the battery and will not provide accurate results.

What will be measured?

During the test, the following data will be taken:

• Battery capacity
• Temperature
• Cell impedance
• Power output
• Discharge time

This can be plotted on a graph and, hopefully, the performance between the new battery and tested battery will not vary too much showing that the battery is capable of performing correctly.

How long will it take?

It usually takes around 5 hours to fully charge and discharge a battery, therefore for the 20 cycles you’re looking at around 4 full days to complete the test.

How about temperature cycle testing?

In some cases, you may wish to measure battery life cycle performance at different temperatures if you know that they’re going to need to be able to perform in different conditions. In this case, the above test will be carried out, but in a controlled environment where they’re subjected to either hot or cold temperatures rather than simply the ambient temperature.

Watch this video where such life cycle testing is explained:

Battery load test (capacity testing)

Perform this test to check whether the battery is able to deliver the correct (manufacturer-specified) power and has the right capacity as expected.

The battery is put under a constant current load (equivalent to the expected conditions that match its expected usage which is likely a constant load at the C rate) and the string and individual voltages are measured.

The time it takes for battery voltage to decline to a predetermined level is compared with the manufacturer’s stated time, then this equation is used to provide an accurate result for capacity:

Battery capacity = time actual / time stated X 100%

Note that some load testing will be carried out with variable load levels, such as for EV batteries.

Watch this video on battery capacity tests which will dig into the equipment used in more detail:

You may also like this blog post over on QualityInspection.org: 4 Ways to Test Battery Capacity on an Electrical Product

Battery self-discharge test

If a battery is left idle, it will self-discharge to a certain degree. Being able to measure the amount of energy that it will lose is important so that:

1. The manufacturer’s claims can be verified
2. You’re able to provide this guidance to consumers

Batteries may be left idle if they’re in storage or in a device that is seldom used. In this case, the user needs to know that the device will power up within a reasonable time-frame and how long batteries may be stored for before losing their charge and/or needing to be recharged.

Different batteries self-discharge at different rates. For instance, a rechargeable LiFePO4 battery tends to have a higher self-discharge rate of around 4.5% per month in comparison to a standard Li-ion battery which suffers from only 1.5-2%.

To perform the test, the battery capacity is obtained (performing a load test will provide this) and when fully charged the battery is left for a period of time, say 24 hours, and the remaining percentage of capacity is calculated by discharging it and charging it once again. This will return the percentage that the battery self-discharged by in the time period – this is usually calculated by the month.

Battery Thermal Discharge Test

As you read earlier, flammability is an issue with Li-ion batteries if they get too hot. Given that it’s possible that a defective battery will heat up too much during normal use, thereby becoming a potential fire hazard, running a battery discharge thermal test is a wise option from a safety perspective.

The test measures how much the battery heats up by when being discharged by normal usage and the battery will fail if it gets above a certain temperature.

To perform the test the ambient temperature will be taken and then the battery will be discharged at 2 volts for 10 minutes. Next, the temperature of the battery surface will be taken and the difference between the two temperatures is the ‘delta’ and is the result we’re looking for. If the delta is higher than acceptable for your battery type, the battery fails. This test is performed a couple of times to return an average delta.

In the example in this video, you’ll see how the battery being tested actually fails because the delta went above the 15 degrees C allowed in the test in the second round of testing:

Note: you may wish to perform a thermal discharge test first as if the battery fails this important safety tests, there is little point in carrying out other performance tests until this issue is fixed.

UN38.3 standard for safe shipping

This testing standard is a MUST for the shipping of all types of Lithium batteries as it is globally required by logistics companies and will prevent transport by any means (air, sea, rail, road) unless passed.

This is because Lithium batteries have been identified as a Class 9 dangerous goods as per 49 CFR 173.140:

For the purposes of this subchapter, miscellaneous hazardous material (Class 9) means a material which presents a hazard during transportation but which does not meet the definition of any other hazard class. This class includes:

(a) Any material which has an anesthetic, noxious or other similar property which could cause extreme annoyance or discomfort to a flight crew member so as to prevent the correct performance of assigned duties; or

(b) Any material that meets the definition in §171.8 of this subchapter for an elevated temperature material, a hazardous substance, a hazardous waste, or a marine pollutant.

So, let’s focus on Li-ion batteries which are most likely to be included in many of today’s electronic devices.

They will need to undergo the following tests that must be conducted by a testing laboratory as UN38.3 cannot be a self-certification:

T1 – Altitude Simulation
T2 – Thermal Test
T3 – Vibration
T4 – Shock
T5 – External Short Circuit
T6 – Impact/Crush
T7 – Overcharge
T8 – Forced Discharge

You may note that some of the performance and safety testing that we’ve mentioned earlier is included in the UN38.3 series of tests (thermal and forced charge/discharge), so it may be that testing to this standard may be enough to cover the most common battery testing for many buyers.

As the supplier of the battery in your market, you need to provide confirmation that the batteries have successfully passed the UN 38.3 test series and include the test summary in your certificate of conformity.

The test summary will include:

1. Name of cell or battery manufacturer
2. The manufacturer’s company and contact information, including full address, phone number, website, and email address
3. Name of the test laboratory that carried out the tests, including full contact details as above
4. Unique test report ID number
5. Test report date
6.  Description of cell or battery including type (Li-ion or Lithium metal), material, mass, Lithium content, energy rating in Watt-hours, model number, and physical description and/or image of cell/battery
7. List of tests and pass/fail result for each one
8. Reference to assembled battery testing requires if needed
9. Reference to the version of the ‘Manual of tests and Criteria’ and any amendments of it used if needed

Remember, your supplier may provide you with a test report, but since this is critical battery safety testing, you may choose to perform these tests yourself with a 3rd party as you are liable for any issues caused by defective batteries.

Good news. For further information about UN38.3 in detail, you can download the full UN ‘Recommendations on the transport of dangerous goods manual of tests and criteria’ here as a PDF for free.

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So, there you have it, a description of the key battery safety testing that we advise and often perform for clients.

What kinds of battery testing are you performing to assess performance and safety? Do you have any questions or issues to share? Leave a comment, if so!

What different types of batteries are suitable for your electronic products?

Sourcing batteries for your new electronic product can be confusing. Selecting the most appropriate in terms of cost, features, and performance can be challenging for buyers…

Get it wrong, and consumers will no doubt complain that the device doesn’t perform well, is too expensive, etc, perhaps resulting in returns or sluggish sales.

That’s why we created this guide to the different types of batteries – hit the button to read it, no download required!