Have you noticed your phone battery draining faster in the heat? There’s a scientific reason behind it. Lithium-ion battery cells, the power source for most devices, are highly temperature-sensitive. When operating at high temperatures, the chemical reactions inside the battery discharge at a fast pace and are volatile and flammable. Electric vehicles (EVs) are powered by lithium-ion battery cells.
Given the record temperatures in the region, tackling the heat challenge becomes imperative to ensure EVs’ sustained viability.
According to Dr. Shayok Mukhopadhyay, a leading researcher and associate professor of Electrical Engineering at the American University of Sharjah, data on the effect of extremely high temperatures on Li-ion batteries is limited. He says that while a substantial body of research is dedicated to characterizing Li-ion battery performance and degradation within the temperature range of approximately 25℃ to 55℃, there isn’t enough on temperatures above 60℃.
Furthermore, he explains that collecting data on battery performance and degradation at high temperatures requires specialized labs and safety measures. “If temperatures continue to rise beyond this point (60℃), the risk of thermal runaway, which can result in sudden and spontaneous fires, increases substantially.” Temperature increase leads to deteriorating battery health and reduced capacity, he adds.
The importance of addressing the effects of heat in Li-ion batteries to ensure their safety and longevity, whether through advancements in battery chemistry, improved cooling techniques, or innovative designs, underscores the need for EVs to gain more credence as sustainable and reliable modes of transportation.
As the world looks to electrify its fleet, several gaps in research question the viability of Li-ion batteries: How do users avoid overheating EV batteries? What is the ecological impact of recycling EV batteries? What are the best practices for EV charging?
OVERHEATING AND BATTERY PERFORMANCE
To view an EV as a ticking bomb in the sun is but a skewed understanding. Research finds EVs are generally less prone to fires than vehicles with gasoline-powered engines.
When it comes to high temperatures, several reactions may trigger one after the other at specific ignition temperatures close to 100℃ or above and may cause an explosion.
Tests with temperatures in the vicinity of 85℃ or higher can only be performed by very well-funded research labs that have the requisite emergency measures and quick-fire suppression measures (hard to do for Li-ion batteries), says Dr. Mukhopadhyay.
This means that the higher the temperature, the amount of data available for characterizing battery performance is not as large. “This may pose difficulty for battery or EV manufacturers to recommend effective safety measures,” he adds.
CHEMICAL REACTIONS AND OPTIMAL CHARGING
Users must be mindful that the heat generated within the battery must be allowed to dissipate to the surroundings so a large portion does not return to the battery itself, raising the temperature further.
Moreover, when an EV is parked, its batteries undergo a series of chemical reactions that affect the overall health and longevity. In this dormant state, analogous to how a flashlight loses power even when turned off, “self-discharge” occurs where the battery loses a small amount of charge.
“Companies may need to invest more in identifying exactly how and when these reactions occur so that battery health may be more precisely modeled,” says Dr. Mukhopadhyay.
He adds that the problem with quantifying the effects of such reactions is usually the inability to gather the required data, as this requires specialized equipment, which requires invasive procedures related to measuring parameters from deep inside a battery.
For a seamless, electrified future, gaps in data must be addressed at the earliest. According to Dr. Mukhopadhyay, finding ways to measure internal battery characteristics or other external measurements, that can offer reliable and precise estimates of particular internal parameters, and then feeding such estimates into an overall battery management system that can react appropriately is the need of the hour.
Maintaining battery pack temperature in the appropriate range via appropriate cooling systems (in hot weather) and heating systems (in cold weather) is also important.
“How to manage the power consumed by such temperature control systems – if the EV has only one power source (the main battery pack) is a challenging problem for the future,” he adds.
HEAVY ENVIRONMENTAL IMPACT
Experts say recycling Li-ion batteries is an environmental burden. Firstly, extracting metals necessitates extensive resource allocation. Mining one metric ton of lithium demands approximately 500,000 gallons of water. While EVs might reduce CO2 emissions throughout their lifespan, their journey starts with a substantial environmental impact due to the manufacturing of their batteries.
“We have to find ways to make it enter what we call a circular lifecycle because the lithium, cobalt, and nickel take a lot of electricity and effort to be mined, refined, and made into the batteries. We can no longer treat the batteries as disposable,” Shirley Meng, professor in energy technologies at the University of California, San Diego, said in a statement to the BBC.
They necessitate a circular approach from inception to end use for a battery.
If you’re an EV owner based in the Middle East, wondering what part you have to play in this – there are dos and don’ts you can follow to maintain the upkeep of your EV battery.
As per Arthi Srinivasan, Director of EV Charging Solutions at Powertech Mobility, a good practice is to avoid charging during peak temperatures in an outdoor parking slot with no shade.
Users should alternate between slow charging (at night) and fast charging.
Srinivasan recommends avoiding charging up to 100%, instead charging mid-range; this helps to optimize the EV battery life and maintain charge capacity.
Users should be mindful of the state of their battery as well. For instance, an older battery at a lower state of charge has a higher internal resistance than a newer one at a higher charge state. Higher internal resistance implies higher heat generation for the same amount of current.
“As a battery ages, the charging and discharging may need to be less aggressive,” says Dr. Mukhopadhyay. Also, if a battery is stored at a higher state of charge (say full charge) compared to a battery at, say, 50% charge, studies report that the battery stored or sitting idle at a higher state of charge experienced greater health degradation with increasing temperature compared to a battery kept idle at a lower state of charge.
As a rule of thumb, battery degradation should be slower if there are fewer increases and decreases in a battery state of charge (in terms of both frequency and magnitude). The key to EV battery longevity isn’t a question about temperature; it is a correlation between acceleration and fast charging. “Frequent rapid EV acceleration and frequent fast charging should be avoided; this is even more important if the ambient temperature is either too hot or too cold,” he adds.
Note to readers: We reached out to a German automaker who declined to respond to Fast Company Middle East’s request for comment.