In the last week, we learned of a recall involving eScooters. This recall came from Lime, an eScooter and eBike manufacturer. However, this is not the first concern about the safety of eScooters and Lime is not the only manufacturer facing consumer safety concerns.
In big cities throughout the world, transportation is being rapidly impacted by more advanced options than those we typically think about: cars, bikes, and public transportation.
Technologies’ rapid advancement combined with the nightmare of slow-moving automobiles and fighting for parking spaces has made Segways and other eScooters an efficient, environmentally friendly, and fun alternative to normal modes of transportation.
San Francisco is 90 miles from our office. On a good day it takes about 2 hours to make it to the city. Upon arriving, I typically want to find a parking place and avoid getting in the car for the remainder of my time in the city. From my interactions, I am not alone in this feeling. In fact, eScooters are a nice alternative to walking around the city and one I plan on trying in the not too distant future. It will allow me to go greater distances in the city, while being fun (because scooters are fun), and I won’t have to fight the traffic in San Francisco.
As with all consumer products and consumer electronics, especially those new to the market, we start to hear stories about the injuries caused and the safety concerns about the new products. eScooter solutions do not appear to be free from these concerns.
Powered by electronics and lithium-ion batteries, we have learned of the potential for fires related to these scooters. You may recall the “hoverboard” fires from a year or two ago. The hoverboards (self-balancing scooters) were a “hot” purchase at Christmastime and then they experienced recalls as a result of battery failures and battery fires.
Again, these recalls are pretty common for consumer products and from my perspective, companies seem to have drastically improved their response to safety issues and rapidly deploy recalls. I seem to see a recall announcement weekly. It is wise to recall a product and prove your company is proactive regarding customer safety. The alternative today, is suffering the Internet-based attacks for failure to do so. Those attacks are likely to be followed by product liability litigation if your customers are injured.
Lime eScooter Recall:
Last week, I read that Lime had recalled some of their scooters from Los Angeles, San Diego, and Lake Tahoe. TechCrunch, among other news outlets, covered the story. The pertinent part of the story is below, some of which was pulled directly from Lime’s blog:
“‘In several isolated instances, a manufacturing defect could result in the battery smoldering or, in some cases, catching fire,’ Lime wrote on its blog. ‘We took this issue very seriously. Immediately upon learning of the defect, we worked with Segway Ninebot to create a software program to detect the potentially affected batteries. We then worked independently to create an even more thorough software program to ensure that no potentially faulty scooters remained in circulation. When an affected battery was identified — with a red code — we promptly deactivated the scooter so that no members of the public could ride or charge it.’
Lime says it then removed those scooters from circulation and ‘at no time were riders or members of the public put at risk.’ But fast-forward to more ‘recently,’ and Lime has received another report that one of its Segway Ninebot scooters may be vulnerable to battery failure. In total, Lime says less than 0.01 percent of its scooter fleet is affected.”
Given the issues with the hoverboards and now eScooters, I wanted to get a better understanding of the issues impacting electronic scooters and the batteries, as the thread that seems to hold all these stories together, is the lithium-ion batteries.
As such, I reached out to one of our experts for his insights on the matter.
Mechanical Engineering, Medical Device and Consumer Product Expert Witness Dr. T. Kim Parnell:
T. Kim Parnell, PhD, PE, is a Professional Mechanical Engineering consultant with strong experience in a number of technology areas. He holds PhD and MSME degrees from Stanford University in Mechanical Engineering and a BES from Georgia Tech. He specializes in the mechanical engineering design and behavior of Biomedical Devices, Superelastic and Shape Memory Metals (Nitinol), Bioabsorbable Polymers, Composites, Fiber-Reinforced Materials, Electronics, and Consumer Products. Dr. Parnell consults actively in these areas using finite element analysis and other advanced technologies to improve designs, to perform failure analysis, and to improve reliability. To learn more about Dr. Parnell, please visit his website: http://parnell-eng.com/.
Nick: In consumer electronics-based batteries, are their common battery defects that may result in smoldering or the battery catching fire?
Dr. Parnell: Yes, there are several failure modes that can ultimately lead to smoke or fire.
External damage is one mechanism that can lead to failure and smoke or fire. By breaching the external battery package, the reactive internal contents will be exposed to air and moisture.
The failure modes generally involve heat and overheating of the battery in some way.
Some of the heating mechanisms are:
- External Short Circuit
- Internal Short Circuit
- Overcharge
- Overdischarge
- External Heating
- Overheating (self-heating)
Each of these heating mechanisms may ultimately result in battery temperature becoming too high.
The elevated temperature leads to gas generation and additional generation of heat internal to the battery.
If this heat generation exceeds the ability to dissipate the heat, a thermal runaway may occur.
If a thermal runaway occurs, then it may be followed by
- venting,
- rupture of the battery container, and then potential
- fire and explosion.
Nick: The article from TechCrunch explains one battery failed and another caught fire. Does a battery have to catch fire to fail?
Dr. Parnell: No. Fire is basically an end failure mode.
Nick: Not just in the instance of these scooters, but more generally, is it possible for a battery to be damaged by the charging process rather than a manufacturing defect?
Dr. Parnell: Yes. The battery may be damaged by the charging process. In particular if the battery is overcharged and if the charge rate remains high after the battery reaches full charge.
Nick: In the article, it seems Lime is able to monitor batteries and detect faulty batteries via software. Can you tell us, in general, how batteries are remotely monitored by consumer electronic companies?
Dr. Parnell: Battery internal temperature is one key parameter that can identify problems. A temperature sensor from each battery cell can provide data that can be remotely monitored and also can be used locally to isolate a cell.
Nick: Can a battery truly be fixed with a software patch? Or, should the defective battery be removed from operation altogether?
Dr. Parnell: A mechanical battery problem cannot be “fixed” with a software patch. A problem battery cell in a battery pack may be identified and electrically isolated.
That is what I’ve got for you this week. Although, it has been brought to my attention (thanks to Kevin Gillespie of TextALawyer), that another blog post about the safety issues in and around eScooter use may be necessary. Stay tuned, as there may be a Part 2.
