Fireproof, explosion-proof – these are the features that sellers of cheap protective bags for lithium-ion batteries use to advertise themselves. Now C’T’s fire test shows that you should not trust such advertising promises. A cheap charging case failed the test completely. Shortly after the first battery cell exploded, flames began to come out of it. After the fire, only a few fragments remained.
Advertisement
For the test, we selected a charging bag for e-bike batteries, which was offered by a Chinese seller on Amazon.de for around 20 euros. It was advertised as “fireproof” and “explosion-proof”. The description said, “The three-layer composite is robust and reliable for maximum insulation against explosions and debris.” As a fire load, we chose a new, fully charged e-bike battery with 375 watt hours – a reasonable rival for the cheap bag, as e-bike batteries with over 700 watt hours exist.
We carried out the test at the company Fisacon in Rheda-Wiedenbrück. It develops charging boxes for batteries, so it competes with manufacturers of charging cases, even if Fisacon boxes are in a different segment with prices above 1500 euros. We chose the bags and batteries ourselves; Fisacon only provided the ignition device and the fire container.
A few minutes after turning on the igniter from a safe distance, the first grey clouds of smoke came out of the bag and five minutes later the first battery cell exploded with a bang. Just ten seconds later the bag caught fire, as shown in our video:
E-Call: Abandoned cell phone triggers massive operationMore exploded cells flew around the fire container without any hindrance. If the test had taken place in an apartment, the battery would have set fire not only to furniture in the immediate area, but also possibly to flammable objects located a few meters away.
We don’t want to spread panic: based on the number of batteries sold, cases of fire are very rare and even when the batteries are externally intact, cases of fire are very rare.
Expert: Bags may do more harm than good
However, in an emergency, a defective bag can do more harm than good. “The heat is concentrated in a pocket, which makes the battery’s chain reaction more likely and even accelerates it,” says Sascha Bruns, battery expert at the Gesellschaft für Werkstoffprüfung (GWP), who has carried out numerous fire tests himself. If several cells explode, the battery can tear or burn the bag and the result can ultimately be even worse than without the container.
Bruns emphasizes that, in principle, a bag does not prevent flammable, health-damaging gases from escaping from it. Because when the electrolyte evaporates its volume increases many times over. If you are unlucky, the gases will ignite outside the bag, causing a dangerous deflagration. This is another reason why it is important to store batteries in as low a fire hazard as possible, possibly under an open window or in a cool enough place outside.
Similar bags are still available
We informed Amazon about the results of our simulated fire test and pointed out that, in our opinion, most bag models in the same price range offer equally poor protection against fire. The company removed the bag model we tested from the platform. “We have removed the relevant product pending investigation,” a spokesperson said. In general, they “proactively remove products in the event of product safety concerns.” However, you can still find many apparently identical models on Amazon.de. Many of these bags are even advertised by sellers as “fireproof” and “explosion-proof”.
You can read more about this topic here:
(CWO)
macOS 15: Apple plans weekly reminders for screen recording permission
