At 9am on Friday 21 August, Krystal Suffling wasn't expecting to spend the day watching a power bank being deliberately pushed into thermal runaway.
Around two hours later, she was at the University of Warwick.
The Telegraph had contacted Firechief® while working on an investigation into lithium battery risks on aircraft. The testing was only confirmed that morning, but it was an opportunity we weren't going to miss.
For Krystal, Firechief’s NPD and Sourcing Manager, the testing itself wasn’t unusual. What was different this time was having The Telegraph there to document a process that Firechief is regularly involved in behind the scenes.
Inside WMG's Battery Safety Centre
The testing took place with Warwick Manufacturing Group (WMG), part of the University of Warwick.
WMG has more than 15 years' experience in battery safety and abuse testing.
Its Battery Safety Centre includes seven specialist test chambers designed to allow batteries to be taken beyond their normal operating limits in a controlled environment.
When Krystal arrived, the WMG team was preparing the equipment while two members of The Telegraph team set up cameras around the facility.
“It felt quite surreal and was exciting to be a part of,” Krystal said. “We do plenty of live product testing, but rarely with such high stakes or with reporters present!”
Photo by: Krystal Suffling
Three tests, one power bank
The team used a new identical model 74Wh Li-Po power bank for each of the three testing scenarios.
It was tested on its own, inside the Firechief® LithShield® Fire Suppression Bag, and finally inside a normal rucksack containing everyday items to create a more realistic travelling scenario.
Four thermocouples continuously measured temperatures at different locations, including the battery cell, heating pad and the internal and external temperatures of the suppression bag.
Photo by: Krystal Suffling
Putting LithShield® through the test
The Firechief® LithShield® Fire Suppression Bag comes in three sizes.
For this test, the largest version, suitable for battery capacities up to 100Wh, was used with the 74Wh power bank.
Photo by: Krystal Suffling
As the battery failed, smoke and gases were produced and the bag visibly inflated. Vapour was able to vent around the zip area.
During this particular test, no flames were observed outside the bag.
That distinction matters.
Testing isn't about creating the neatest possible demonstration. It's about seeing what actually happens under controlled conditions, measuring it and learning from the result.
Once the test was complete and it was safe to do so, the bag was opened and the remains of the battery inspected.
Credit: WMG, University of Warwick.
The test that didn't go to plan
The final test placed the power bank inside a normal rucksack. It was filled with items you would usually see in a bag, such as clothes, notebooks, and a laptop.
Everyone waited for the expected fire.
It didn't happen.
The battery reached temperatures above 300°C, but the rucksack initially refused to ignite. The team spent longer on this test trying to drive the battery fully into thermal runaway.
Eventually, with little apparently happening, most of the team packed up and went home.
Hours later, WMG returned to check the chamber.
The rucksack was on fire.
What initially looked like the least dramatic result became one of the most interesting parts of the day.
It was also a reminder of how unpredictable battery testing can be. An apparently quiet period did not mean that the event was over. Krystal highlighted this after the test as one of the things that made the day particularly interesting.
The part of Firechief® you don't always see
Days like this show another side of what happens behind the scenes at Firechief®.
Product development isn't simply a finished product appearing on a website. It involves working with specialists, asking questions, testing, observing and learning from what actually happens.
What began as a last-minute phone call became an opportunity to spend the day alongside WMG and The Telegraph, seeing lithium-ion battery behaviour first-hand replicated in a real-life scenario.
Sometimes the most useful test is the one that doesn't follow the script.
See the testing in action
Credit: WMG, University of Warwick. Remains of the rucksack and contents after the fire. Just to demonstrate how bad the rucksack fire actually got in comparison to our fire suppression bag which is relatively unscathed.
The Telegraph's investigation, “This is what happens when a power bank explodes on a plane”, includes footage from the testing and looks more closely at the wider issue of lithium batteries in aviation.
Read The Telegraph investigation
Find out more about LithShield®
Firechief® LithShield® Fire Suppression Bags are available in three sizes for different battery capacities.
The largest version, suitable for battery capacities up to 100Wh, was the version used during the WMG testing with the 74Wh Li-Po power bank.
Important information
The testing described in this article was carried out by Warwick Manufacturing Group under controlled conditions using a specific 74Wh Li-Po power bank and defined test setup. The observations relate to those individual tests and should not be interpreted as a guarantee of performance in every battery incident.
Battery behaviour can vary depending on chemistry, construction, capacity, condition, state of charge and the surrounding environment. Always follow product instructions, applicable fire safety guidance and the fire risk assessment for your premises.