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The Importance of Ebike Battery Safety and Fire Prevention
*This informative article was originally published by LEVA and is now being republished on Electric Bike Report for our valuable readers.-Edward Benjamin-Chairman, Light Electric Vehicle Association
Within the confines of my garage, resides an electric bike equipped with a battery capable of providing enough power to propel not only my 100 kilogram physique but also the hefty Pedego Stretch Cargo Bike, laden with various cargoes (often exceeding 50 kilos of SCUBA gear), at a consistent speed of 20 miles per hour (32 kilometers per hour) for an extended period of time… well over an hour, to be precise. Remarkably, I have never completely depleted the battery’s energy reserve.
Attempting to comprehend the exact amount of energy required to propel my weight, along with the cargo and the bike, at a continuous speed of 20 mph for an extended period, warrants the expertise of a physicist. Sadly, I lack the competence to calculate this intricate measure. Nonetheless, I can confidently affirm that the battery unit housing the tremendous energy density is similar in size to two cigar boxes (or a single shoe box, fortunate for those who don’t indulge in smoking cigars).
Sustaining such a pace of 20 mph consistently necessitates a high current draw (exceeding 30 Amps) to power the wires, connectors, circuit boards, and the exceptionally efficient motor. Decades ago, this level of strain on a lithium manganese battery could have potentially led to an alarming situation where a fire could have ignited. However, in today’s world, fires resulting from such scenarios are incredibly unlikely when it comes to my bike.
Several Compelling Reasons for this Remarkable Result:
1. Sophisticated Battery Management System (BMS) and motor controllers: Unaffected by the intensity of my bike’s performance, the microchip-controlled BMS and controller are equipped with software designed to safeguard the components, curbing any possible danger of a fire. They achieve this feat by constantly monitoring the current consumption and effectively limiting or ceasing it if required. In addition, the BMS includes a temperature sensor, often a thermistor, which facilitates the flow of current when a specific heat threshold is reached, thereby notifying the BMS of the elevated temperature within the battery module. Consequently, the BMS can take action by either shutting down or restricting the current flow using innovative solid-state switches known as MOSFETS (metal–oxide–semiconductor field-effect transistors). Furthermore, the BMS is programmed to prevent overcharging, over-discharging, respond to short circuits, and carefully monitor the battery’s state of charge. The outcome of these advanced features is a controlled shutdown and a waiting period while the system cools down. Alternatively, this may result in certain limitations on usage, which, in all likelihood, go unnoticed to the ordinary user.
2. Integrated Safety Features within the Battery Cells: Ebike battery packs are often equipped with one or more preventive measures, including a component within the cells to control high-current surges and a safety vent that effectively releases excessive pressure gas resulting from any potential malfunctions.
3. Choice of Battery Cell Material: The most commonly utilized material in ebike batteries, Magnesium Spinel, inherently possesses remarkable stability. While it is true that all batteries have the potential to catch fire, Lithium Magnesium Spinel (LiMa) cells provide a stable and reliable solution due to their optimal energy density and cost-effectiveness. These cells are designed and engineered to maintain stability even under extremely high temperatures, surpassing approximately 250°C, which is undeniably scorching hot!
4. Intelligent Charging Solutions: Battery fires frequently occur during the charging process. Therefore, deploying a high-quality charger capable of monitoring the charging process, detecting the state of charge accurately, and shutting off once the battery is fully charged plays a crucial role in preventing potential mishaps. Some chargers are even equipped with thermal monitoring capabilities, allowing them to measure the battery’s temperature during the charging phase. Additionally, certain chargers are designed to exclusively function with a specific electric bike model, preventing any incongruities.
5. In recent times, we have witnessed the emergence of cells and battery packages that possess superior design and the ability to endure high rates of discharge and charge. These advancements signify important lessons learned and commendable progress in the field of technology.
The key takeaway?
It is highly unlikely for an electric bike to experience a battery fire. Considering the staggering number of approximately 300 million electric bikes being utilized worldwide, occurrences of fires are so rare that they manage to grab headlines and capture attention on platforms like YouTube.
However, there is always a caveat – a word derived from Latin, which imparts a sense of intellectual superiority due to its connotation of a warning or limitation.
The crucial components present within battery packages, which make them highly unlikely to cause any trouble, include quality cells, meticulously designed battery packages, expertly crafted battery packages, precisely engineered and manufactured battery management systems, efficient BMS software, impeccable charger design and manufacture, excellent motor controllers, and responsible e-bike owners/operators.
Renowned brand name bikes typically possess these essential elements (although the credibility of the bike owner may be questionable…), and both the bike and battery (along with the charger) undergo extensive testing, often showcasing certifications such as CE, UL, BATSO, and others. Additionally, there are high-quality bikes from lesser-known brands, which also undergo thorough testing and use only top-notch components in their construction.
However, complications may arise with damaged bikes, bikes constructed at home, DIY kit bikes, inexpensive bikes, bikes intended for excessive speeds, or errors in engineering or production. These are the types of bikes that often encounter problems.
Issues can occur when the product manager, responsible for overseeing all aspects of bike production, realizes the exorbitant cost of the battery and attempts to save money by opting for a cheaper alternative. This leads to compromises in design, materials, and features, which predominantly affect the bikes with lower price points.
Now, let’s discuss how to safeguard yourself from a fire and the appropriate steps to take if one does occur.
Large-scale lithium batteries have the potential to trigger intense fires that are incredibly challenging to extinguish. The resulting smoke and vapors are toxic, and extinguishing the flames does not necessarily imply that the incident has concluded. The substantial amount of energy stored within the battery continues to generate heat, causing the battery to reignite even after being extinguished initially.
This phenomenon is commonly referred to as Thermal Runaway.
And there’s more.
To further enhance safety measures, consider setting a timer to restrict the duration of the charging process. An uncomplicated current timer available on platforms like Amazon, priced at approximately $20.00, can be configured to automatically turn off the charger, alleviating any concerns even if you happen to forget.
Furthermore, ensure that you charge your bike or battery in a clean and dry location, devoid of any flammable substances located above, below, or in close proximity to the bike or battery. (Allow me to recount an unfortunate incident involving a charging battery that ignited below a shelf housing gallon containers of isopropyl alcohol and acetone. Needless to say, it was far from a joyful story.)
I also have a few anecdotes to share about batteries overheating and catching fire while charging on wooden work benches, resulting in the destruction of bike shops.
Remember: When charging the battery or bike, choose a location from which you can quickly remove the bike or battery from the premises if you detect any peculiar smells, vapor emissions, smoke, and so forth.
Have a smoke detector installed above the area where you charge your devices.
And now, let’s talk about what to do in case a fire breaks out despite your precautions:
First and foremost, prioritize the safety of everyone present by evacuating the building immediately. Dial 911 to contact the fire department and ensure their prompt arrival. Afterward, assess if you are capable of performing any of the following actions. If you can’t guarantee your safety, refrain from attempting.
1. Avoid inhaling the toxic fumes and smoke. They can cause severe harm to your health. Do not touch the battery, as it is extremely hot and likely to disintegrate. Additionally, the cells might explode, scattering burning materials around.
2. Utilize a fire extinguisher to extinguish the flames. Almost any type of extinguisher will suffice, including water extinguishers or hoses. In my workshop, I always keep a few ABC extinguishers.
3. Cool down the battery pack. Merely extinguishing the fire won’t prevent re-ignition, as the thermal runaway resulting from the stored energy in the cells continues to generate heat. Use an ample amount of water for this purpose.
4. Continue cooling the battery pack. I have a hose connected to a water source that I can employ for this task. Additionally, I keep a bucket as a backup. Remember to avoid inhaling the fumes.
5. Keep the battery pack cooled.
6. Continue to cool the battery pack.
7. By this point, the fire department likely will have arrived and they will likely continue cooling the battery pack. Once they determine it is no longer hazardous, it will be appropriate to relocate it to a secure area, such as the parking lot or driveway.
8. The remnants of the battery pack are of interest to various parties, including the insurance company, the manufacturers and sellers of your bike, and the individuals responsible for designing and manufacturing the battery pack, Battery Management System (BMS), and cells. Take photographs and document what occurred. Keep the battery remains intact and readily accessible for inspection.
9. If you experience a fire incident, please send me an email detailing the situation.[email protected]