This post covers Key Takeaways and Frequently Asked Questions for Honeywell’s Sensor Approach for Lithium-ion Battery Safety. Whether you’re a seasoned professional or a curious newcomer, you’ll find plenty of valuable information watching the webinar. Links to the Webinar, Resources, and Related Content are at the end of the post. A copy of the PowerPoint presentation will be provided for customers that register to watch the recorded webinar. All Snips and Content Compliments of Honeywell Sensing and Safety Technologies.
Company name: Honeywell Sensing and Safety Technologies
Training Date: 3/29/2023
Ajibola (AJ) Fowowe, Sr. Offering Manager, Honeywell Sensing and Safety Technologies
- Ajibola (AJ) Fowowe is a Sr. Offering Manager at Honeywell Sensing and Safety Technologies, leading sensor development for electric vehicles.
Fan Yang, Ph.D. Sr. Advanced Systems Engineer, Honeywell Sensing and Safety Technologies
- Dr. Fan Yang is a Sr. Advanced System Engineer at Honeywell Sensing and Safety Technologies. Dr. Fan has a Ph.D. in Mechanical and Electrical Engineering with and extensive background in battery safety.
LFP (Lithium-Phosphate) Characteristics
- lower cost
- longer life cycle & lower thermal runaway risks
- lower energy density
- more sensitive to cold temperatures
NMC (Lithium, Manganese, Cobalt) Characteristics
- Higher energy density
- Better charging performance in cold climate
- Higher cost
- Shorter cycle life and higher thermal runaway risk
The focus of this webinar is on the peak detection of thermal runaway in Lithium-Ion batteries, which are commonly used in Electric Vehicles (EVs) and Battery Energy Storage Systems (BESS). The batteries now account for a significant portion of the vehicle’s total cost, ranging from 30 to 50%, due to the advancement in battery technologies such as solid-state and flow batteries. To address the high costs, researchers are exploring ways to extend battery life and reduce safety concerns related to overheating.
When it comes to selecting the appropriate battery type, NMC cells may be the better option for applications requiring high energy density in small batteries, such as electronics, laptops, phones, EVs, renewable energy storage systems, portable power stations, etc. These cells have a cycle life of around 2000 to 2500 cycles. On the other hand, LFP cells have a typical cycle life of 5000 cycles and can last up to 7-10 years before degradation. They are a better choice for battery storage applications that require long cycle life, thermal stability, or higher quality, such as EVs, solar systems, and leisure vehicles like motorhomes, boats, etc.
And, It’s worth noting that NMC cells tend to release 70% of their capacity at low temperatures, such as -20°C, while LFP cells release only 55%. However, from a safety standpoint, LFP cells would be the better option since NMC cells can be more prone to causing fires and explosions due to the chemistry of the cell.
So what is thermal runaway in Lithium-ion batteries?
Thermal runaway is an uncontrolled process that can occur in a battery cell, where a series of exothermic reactions leads to a rapid increase in temperature and pressure within the cell, ultimately resulting in its breakdown. This process can occur within a few months or instantaneously, causing the battery to enter an uncontrollable self-heating state. Can be triggered by a number of factors, including overcharging, exposure to high temperatures, physical damage/puncture to the cell, or the presence of impurities or manufacturing defects. Once thermal runaway has started, it can be difficult to control or stop, and can quickly spread to other cells in a battery pack.
In the webinar, Honeywell will discuss their sensor approach to detecting thermal runaway at an early stage, by employing an (BAS Aerosol Sensor) to detect abnormal levels of particulate matter and a (BPS Pressure Sensor) to observe any fluctuations in pressure, which could be potential indications of thermal runaway.
Following the presentation, you can expect to have a clearer comprehension of thermal runaway and the various safety measures employed in current battery applications. Additionally, you will gain knowledge on which sensors are suitable for your specific application.
For my battery pack design, do I need to use a combination of the BPS and BAS sensor?
The combination of both sensors will work in your battery pack design. However, one BAS or one BPS may be sufficient. The battery design team will need to consider the battery pack architecture to determine which sensor type and QTY is most ideal.
Can the BAS and BPS sensors be used in non-automotive application?
The BAS and BPS sensors were primarily designed for automotive applications but can also be used in non-automotive applications. Today, we have customers using these sensors in stationary energy storage systems.
In your presentation, you highlighted gases are released during stage 1 of thermal runaway. What gas sensors do you recommend for this?
“There are two sources of gas generation: (1) The vaporization of the solvents (DMC, EMC, DEC, EC, etc.), once the temperature rises to the boiling point of the solvents, they will gasify and vent from the cell. (2) The gas generated by the decomposition of cell components.
Different gas sensors can be used in this scenario, like photoionization detector to monitor voletile organic compound (VOC), like NDIR sensor to monitor gases with special absorption spectrum, or MOS-type sensor to detect reducing gases.”
I thought this webinar was more about smaller batteries. I would like to know what is risky temperature of Li-ion batteries, like a 7.2v 3300mAH while being charged?
All lithium-ion batteries share similar architecture. The common battery cell types (NMC & LFP) have different temperatures for which they become unstable and very likely to go into thermal runaway. NMC have a lower thermal runaway threshold of 210°C but at 100°C, they may become unstable. For LFP, they have a higher thermal runaway threshold of 270°C but at 170°C they may become unstable. This is why engineers usually use different cooling (liquid or air cooling) to prevent the battery cell temperatures from getting to these unstable thresholds.
I would like to know if these explosion risks increase marginally with charge current?
I mean if we charge 0.5C compare to 0.75C or 1CCharge current will lead to increasing temperature and therefore
Thermal runaway is primarily triggered by temperature. And yes, you’re correct because a larger charging current will lead to a higher temperature and if not cooled appropriately may lead to thermal runaway. Today, battery makers are focusing on high-efficiency cooling system design inside the battery pack.
Is thermal runaway an issue in smaller batteries? such as batteries used for program memory storage, 2032 batteries are common. if it is an issue are there safety sensors designed for smaller batteries?
Thermal runaway applies to all lithium-ion batteries cells and safety must always be a consideration. 2032 battery cells are smaller in size and have a matured design. Typically, they are more reliable. However, if exposed to excessive heat, the cell will go into thermal runaway. Considering the size and since most 2032 battery cell application only require a single cell, you will not have thermal propagation to other cells and the explosion may not be as catastrophic.
Where can we find the BPS test information?
BPS test information will be published at a later date.
How do the batteries compare in terms of recyclability?
“LFP batteries are relatively easier to recycle compared to NMC batteries. LFP batteries use non-toxic and non-hazardous materials, and their cathode materials are simpler, which makes the recycling process more straightforward.
The cathode materials in NMC batteries contain cobalt, nickel, and manganese, which are valuable metals that can be recovered and reused. However, the process for recovering these metals is more complicated and requires more specialized equipment.”
Will regulations recognize the safety advantages of LFP over NMC (ie different/fewer safety requirements)?
At this time, we are not aware of any regulation that specifically considers LFP vs NMC. Most regulations treat them the same.
Are there any applications for sensors to mitigate risk when shipping battery cells or packs?
Risks of thermal runaway is lower when the battery is not in use.Safety during shipping of battery cell or pack is an interesiting topic, and theoretically BAS or a fixed gas instrument can be used in this scenario.
Do you have data logs from sensors during thermal run away ? is it possible to see it?
The BAS and BPS sensor does not have data logs. Data is sent to the battery management system via the CANBUS.
What VOC do you expect to see ? I believe you are using Tvoc sensor now ?
For this experiment, we used Honeywell’s battery safety aerosol sensor. Honeywell offers an aerosol and pressure sensor for thermal runaway detection. In addition, Honeywell recently signed a licensing agreement with Nexceris for access to their Li-ion Tamer technology. Later this year, Honeywell will introduce a sensor using Li-ion tamer technology for VOC released during first vent i.e. before other byproducts such as hydrogen, carbon monoxide, hydrocarbons, and esters.
With Chevy Bolt, how is the battery problem detected?
This is a good question. We recommend that you check with the vehicle manufacturer to understand the safety sensors used in your Chevy Bolt battery pack. Feel free to highlight Honeywell’s BAS and BPS sensors for their consideration.
Resources and Related Content:
Link to Webinar: The Sensor Approach — Ensuring Lithium-ion Battery Safety in the Era of Electrification
Link to Webinar Center: Webinars free, live and on demand
Supplier Center Honeywell Sensing & Productivity Distributor
Honeywell Safety Pressure Sensors: