New research from the University of California, Riverside, has demonstrated how the heat generated by fast-charging can significantly damage EV batteries.
Engineers from UC Riverside (UCR) experimented on Panasonic NCR 18650B cylindrical lithium-ion batteries of the kind found in Tesla vehicles. Using the same industry fast-charging method as deployed along US freeways, they found that after just 40 cycles, the batteries were achieving just 60 per cent of their original capacity.
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“Industrial fast-charging affects the lifespan of lithium-ion batteries adversely because of the increase in the internal resistance of the batteries, which in turn results in heat generation,” said UCR doctoral student Tanner Zerrin, co-author of the study, published in Energy Storage.
After 60 charging cycles, the industry method battery cases cracked, exposing the electrodes and electrolyte to air and increasing the risk of fire or explosion. High temperatures of 60 degrees Celsius/140 degrees Fahrenheit accelerated both the damage and risk.
“Capacity loss, internal chemical and mechanical damage, and the high heat for each battery are major safety concerns, especially considering there are 7,104 lithium-ion batteries in a Tesla Model S and 4,416 in a Tesla Model 3,” said Mihri Ozkan, a professor of electrical and computer engineering at UCR.
To counteract the damage caused by this type of fast-charging, the researchers developed their own fast-charging algorithm that monitors and adapts to the battery’s internal resistance. This significantly reduced battery degradation compared with the industry-standard fast-charging. Batteries charged using the industry method fell to 80 per cent capacity after 25 charging cycles, while internal resistance method batteries lasted 36 cycles before reaching this point. What’s more, this technique did not result in the catastrophic failures witnessed using existing fast-charging methods.
“Our alternative adaptive fast charging algorithm reduced capacity fade and eliminated fractures and changes in composition in the commercial battery cells,” said Cengiz Ozkan, professor of mechanical engineering at UCR.
The researchers have applied for a patent on the adaptive internal resistance fast-charging algorithm that could be licensed by battery and car manufacturers.
So while people continue to try and devise a foolproof power dense battery system which seems to generate unforeseen negative consequences, why is there not a drive to find an alternative way of packing that energy in? Hydrogen and fuel cells (or even direct burning of hydrogen) comes to mind which offers longer lifetime and almost limitless flexibility compared to the fixed charging infrastructure needed for batteries. This has the separate advantage of not needing battery recycling facilities and eliminates demand for the materials to make batteries in the first place. Fuel cell systems can use exactly the same motor and transmission systems as any EV, replacing the heavy and bulky batterries with a liquid fuel tank for much greater energy density and capacity.
Most EV’s (apart from Nissan Leaf) have battery thermal management to prevent damage to the expensive battery from rapid charging, E.g. my Renault Zoe has lost 3% of its original capacity after 100 – 150 Rapid Charge cycles and 21500 miles on the clock of 13 months use.
Hydrogen is 3x less efiicent than electric vehicles when you include Hydrogen production from Renewable electricity, transportation, liqufaction or compression and losses in the fuel cell and electric motor. Petrol cars are 4x less efficient than electric vehicles. Average hydrogen passenger vehicles cost £60k average electric passenger vehicles cost £25k, discuss.
To put in perspective how bonkers what they are doing to these batteries is, in order to reproduce 60 of these charge cycles in a live vehicle, you would have to:
1. Completely disable any thermal management system in both your vehicle and a fast charging station.
2. Drive the vehicle until its dead at 0.5C. For a Chevy bolt, that would be 30kw draw, which would maintain 80-90mph on level ground.
3. Charge it at a fast charger station that once again completely ignores the battery temperatures (assuming the vehicle will even allow charging at up to 2C, which our bolt does not, but just pretend).
4. Repeat 60 times (in that chevy bolt, that would be 9,600 miles, or across the US 3 times), only taking a break every 10 (1,600 miles).
No one ever will do that to a vehicle and expect it to live.
The quality of the paper in article is questionable. Automotive grade cells do not show such drastic reduction in capacity after only 60 cycles. The Panasonic 18650 is an precious gen cell no automotive use anymore. Their ‘industrial charging method’ is nothing more than a step charge up to 2C C-rate, a lower CC phase then a CV hold. Constant current at 2C can be very damaging to subpar cells at moderate to high state of charge. This is such a basic charging method nobody uses in automotive industry. I am not even sure what ‘industry’ they refer to. Diagram of fast charging power vs time are available on the Internet of major EV cars and none of the OEM uses CC-CV fast charge like this.
The Panasonic 18650B cell is one of the least suitable cells for fast charging that is on the market. If you charge and discharge lithium cells at a rate that does not get them warm or hot, they will last a very long time.
So they took the previous generation of cells, removed them from from their battery back and thermal management system, completely removed the vehicle’s charging control systems, and subjected them to very high power charging. Are they actually surprised by the result?
I would think that the super capacitor technology is most visble option and the most cost efficient.
More research should br availed to it. Its much more safer and environmentally friendly.
Regarding Hydrogen, I believe it solves not only the electric car range problem, but also the spare (wind, solar) energy storage problem. Why is this technology not being fast tracked?
Tom Foreman’s info about his Renault’s battery performance is very interesting. It shows that the problems are being overcome and electric cars are getting nearer to being sensible purchases: I’d still buy a diesel myself as I like range and easy filling, but if I did in-town driving I’d look at at differently.
Would note that Tom’s comparison of efficiency of I/C versus electrical drive forgot to allow for conversion to electricity and transmission of this, which reduces the difference massively. Also, EVs do not pay any fuel tax, which greatly distorts the market.
Shaun: Evidently, you have NOT seen what happens when, for any reason, a large capacitor bank is shorted: A huge kind of “explosion”. Years ago I had a friend that worked repairing all kinds of electronic equipment, from TVs to large Radars and some industrial equipment. One day he was repairing a professional photographer’s Studio Flash when by accident, he moved the apparently defective wire harness, and produced a short circuit. The resulting fast discharge reached such a large instantaneous current, that it vaporized not only the harness wires, but the large screwdriver tip he was using to remove the nylon ties that held the harness in place. The “explosion” left hundreds if not thousands of copper and steel droplets impressed under the ceiling of his shop, and the sound was akin to a large caliber firearm shooting.
The problem with large capacitors, is that contrary to batteries that present some internal resistance, the capacitors have almost none, there lies their danger. If a large capacitance to yield enough energy to propel the vehicle for any reasonable distance, the stored charge can be quite dangerous during a mishap, inevitably.
Nick (and others) : If you think batteries are heavy and bulky, run some fast numbers (“Napkin calculations”) for comparing to either the thick-walled, large storage tanks or cryogenic ones, or the adsorbed or absorbed metals or substances needed to store Hydrogen. It is a matter of “energy content density”. For a hard and fast fact: Gasoline packs MORE punch than Dynamite, both by mass and by volume. If you have trouble imagining that, picture a cylinder packed with explosive, like those grenade launchers used in WW-II on surface ships against submarines… but replace the grenade with a small sedan. Now replace the explosive with plain gasoline and enough oxygen for complete combustion: a single liter of gasoline would launch the car to a distance of about 15 or more miles away (!)… That is the reason for gasoline or diesel yields: a large energy density. Hydrogen is MUCH less energy-dense, plus it requires a lot more difficult containment to carry it on the vehicle. About 2,700 times less dense than gasoline.
The development of batteries is very creditable and offers many useful applications. It is unfortunate that politicos have managed to make this a virtue issue and throw out the well developed I/C engine in the UK, France etc.
The rest of the world will gratefully take up these products as they progress, with low-cost oil to make things even better. However, we can sit back and say look at all the CO2 that we have saved – pity that it did not reduce the world figure!