Now, here’s the story you’re after: We’ve all wondered why EVs cap out at eighty percent charge, and it turns out there are two elegant reasons. First, you need headroom for regenerative braking — nowhere to put that recovered energy if the battery’s already maxed. But the second reason is more fascinating. We think of filling a battery like filling a gas tank, but it’s nothing like that. Every electron has to find its specific spot in the lattice structure. So imagine an auditorium full of seats. You can pack people in fast until it’s mostly full, but then each person has to hunt for their individual seat. After eighty percent, those remaining electrons face exponentially more work finding their spot, so charging slows dramatically and degrades the battery faster. That’s why the last twenty percent takes forever and does real damage to cell life.
Now, CATL
CATL held their Super Technology Day yesterday in Beijing and announced six major battery innovations — third-gen Qilin, third-gen Shenxing superfast charging, sodium-ion scaling, and more. But I’m not seeing an official slide deck or PDF on their main website yet.
The third-generation Shenxing Superfast Charging Battery. It’s an LFP chemistry with 280 watt-hours per kilogram cell-level energy density and 600 watt-hours per liter volumetric density. It charges from 10 to 98 percent in 6 minutes and 27 seconds under normal conditions, and even at minus 30 degrees Celsius it goes from 20 to 98 percent in about 9 minutes. The tradeoff is after 1,000 complete charging cycles it loses roughly 10 percent of its capacity. No pricing disclosed yet.
This battery defies my example of filling an auditorium. We don’t know everything about it yet. We don’t know how long it lasts if you don’t smash it full of electrons. We don’t know how much it costs, and we don’t know what the actual pack density is. We can guess based on other LFP batteries that kilogram for kilogram, it will provide 20 percent more range than current LFP batteries.
For me that is pretty exciting. A Model Y currently has about a 320 mile range. A 20 percent increase would put it at about 380 miles. Quick charging to 80 percent would give about 300 miles range. My experience with various cars is that about 300 to 320 miles of range is comfortable. My Toyota Venza gets about 280 miles and I find that has me stopping more often than I like. My Ram 1500 has about 380 and that seems very roomy. So, if the price for this battery is reasonable, then this could be the one that leverages over the system from gas to electric. As the company has not released the PDF’s and slide deck, we are just looking at news reports and not what the company actually said. That will have to be a later date.
That is a good question. I am guessing that the forcing of electrons in creates heat and the heat damages stuff, but this is way over my training so I do not know. Just my intuition, if they don’t fast charge this battery to 90 plus precent it might not degrade as much. We will have to wait for at least the slide decks and PDFs from CATL for the presentation and even them probably have to wait for a lot of third party testing and analysis.
The instructions with my Ioniq6 says to charge it to 100% once a month. An explanation in an Ioniq6 groujp gave the “parking lot” rather than “auditorium” analogy, but same thing. When you charge you are “parking” electrons. Like a shopping center lot, when it’s near empty you can park anywhere. As it fills up it gets harder, until the lot is 80% full and you are driving more slowly around looking for an open slot. When the lot is 95% full you may have to drive all the way to the other side of the mall to find it, and that takes time. That’s why fast chargers will run at top speed to 80%, then slow down and slow down and slow down as they get close to 100%, for fear of jamming electricity where it doesn’t belong, overheating a cell, and doing long term damage if not actually causing a fire.
But there is nothing wrong with charging to 100% so long as you do it appropriately. (You should not, however, store at 100% for long periods of time.) I have Anker batteries attached to my solar panels, they charge to 100% regularly, as they are designed to do.
For the record, even at 100% there is room for some regenerative braking, but perhaps not if you are descending from Pike’s Peak and using it all the way down. (The 100% is a slightly false reading, tuned down to insure the charge doesn’t go over. Slightly less is better than slightly more.)
Funny you mention that. The owner’s manual of my ZDX states to not fully charge in situations exactly like this - to leave room for regenerative braking on descent. Since EV’s tend to be heavy, friction braking on long steep descents is more problematic than for more ordinary cars.
The electro-chemical processes cause a spike, called a dendrite, to grow inside the battery. Those dendrites have been a huge problem for a long time as they distort both the mediums but also pierce the barriers between them.
A lot of work has gone into chemical make ups that do not grow these crystals/dendrites but they do still happen. This basically destroys the ability of small parts of the battery and they add up over time.