Charging lithium-ion batteries at high currents first increases lifespan by 50%
eurekalert.org
eurekalert.org
Not to mention, how much does the increased SEI change the impedance of the cell (thus reducing the subsequent charge speed) and the capacity available.
https://electrek.co/2023/08/29/tesla-battery-longevity-not-a...
Plenty of engineered things could be "better" if price wasn't a concern. Most of this board can probably think back to a time where they had to leave long term value on the table because of short term costs concerns. It doesn't seem impossible to me that the engineers would leave some battery longevity (something that's hard to gauge for the consumer) on the table in pursuit of faster charging speed at lower prices (headline marketing items).
If only for a city only car that you mostly charge at home, don't do roadtrips with multiple fast charges in short period of time you may get away with passive cooling. And if you don't live in a hot climate. But those are too many IFs.
Charged at home >50% of the time and pre-pandemic on the 6.6kW chargers at work. I can only recall one attempt we made at a beyond single battery trip, using an EVGo DC charger at the mid-point. I can say it worked, but subsequent trips to that same location were in the ICE car, so take of that what you will.
The car is now 80+% charged at home and is a city/nearby suburb runabout (and used for more trips, albeit not more miles, than the other ICE/hybrid).
It still has about 85% of its original battery capacity, which means we charge it about once a week, which works just fine for us.
It is healthy to know how to maintain car battery. I will probably charge the battery to ~80% except when I need more range.
It’s down 1 bar (of 12) and that was 2 years ago, so the 85% is estimated, but is within -0% to +4%. I have a LEAF Spy but haven’t checked it a long time.
So: higher voltage implies lower heating.
Energy loss though resistance in the pack's internal wiring is likely a lot less than the loss due to the chemistry not being 100% efficient at absorbing (or delivering) charge without heating up. But it does allow for thinner wires to get max power out of the battery.
There should be less heating for higher voltages but if most if the heating is in the battery vs the distribution system then the higher voltages will not help much.
Also, if they make all wires smaller to save money and weight then there might not be any change in heating.
I think the higher voltage allows them to charge more of the battery pack in parallel at a time.
All LiIon and LiPol chemistries have shown the following:
1. deep-cycle discharges below 60% full cuts usable charge cycle counts from 8000 to under 2000 uses.
2. high-current discharge or rapid-charging accelerates capacity losses by about 15% a year
3. Internal resistance goes up as dendrite defect shorts damage the cell. Additionally, the self-discharge rates increase as the cell is degraded.
Very surprising if the technique works for all cell chemistries. =3
This study solely focuses on the very first charge. It doesn't claim that recharging at high currents benefits battery life, only that the first charge at high current forms a larger protective barrier than a first charge at a low current.
Other studies have shown that a larger protective barrier improves lifespan. (See other comments on this thread for more details on the science.)
i.e. they would drop into a constant-voltage rapid charge mode assuming the cell was prepped already.
None of these systems showed any sort of increased capacity or longevity. Quite the contrary results, this is why the new study details are rather intriguing. =3
When they say "very first" they mean it very literally.
In general, we track the internal resistance (+-0.02ohm for Samsung) of the inventory under both new, charged, discharging, and storage levels. While I don't doubt the Papers results, they need to be clear on the methodology so others can validate it is not BS (common in this area.)
Have a nice day =3
It is fascinating news, and I look forward to more details. =3
> 1. deep-cycle discharges below 60% full cuts usable charge cycle counts from 8000 to under 2000 uses.
Presumably these are NMC variant?
Major Chinese LFP brands come with 6000K/10K cycle guarantees (but with specific operational parameters). Are these cycle predictions unrealistic ?
catl/eve/etc
That is, if you do it single time you are down from 8k to 2k? Or it decreases gradually and 2k is the worst case?
Where can I read about it? Not a paper, but something more down to earth for consumers? That is, for a consumer to know how to properly maintain various devices (phone/car) for longevity?
That said, I previously read studies suggesting to keep the batteries between 30-70% SOC for optimal longevity, though I imagine there's been a lot of research so it might be now outdated.
In general, "the battery is the car" for EVs... The bigger the better in my opinion, as it will last longer due to reduced stress on the cells.
Even if people are stressing the vehicle pack, they should still get 5 to 12 years out of the car. Note, some companies hide the expected range loss by over-provisioning capacity.
Best regards, =3
This is definitely true, recently faced issues with my motorbike battery and oh boy are they fragile and lose charge by themselves quickly compared to bigger car batteries.
Basically I left a few times older (10-15 years) diesel bmw standing whole winter without touching it, started always without any issue (I know not the best idea re fuel in the tank, but it worked).
I did that once to completely new motorbike (honda) with good brand battery but I didn't unplug it, and now battery is permanently damaged and loses full charge in less than 2 days to such levels that it can't start the engine even if those 2 days its completely unplugged.
Tip: if a Pb pack is partially discharged, it is more vulnerable to cold-weather related standby failures. Most people that own boats/heavy-equipment get a plug-in trickle-charger for Pb batteries, as the adapter also helps keep the pack slightly warmed.
Best of luck, =3
I don't want to get into the name-and-shame game with other manufacturers. The 3 brands mentioned are generally very good quality, and if you can source new cells without counterfeit/expired nonsense... they will perform as per their app notes.
The cycle limit is a function of whether your charger IC is smart, slow-charge/low-current-discharge, and if your firm uses capacity Boosting (stress costs cycle counts.)
>Or it decreases gradually and 2k is the worst case?
Anecdotally, sensitivity seems somewhat correlated with cell use/age. The more stress, and the faster the cell degrades.
Best of luck, =3
> Removing more lithium ions up front is a bit like scooping water out of a full bucket before carrying it, Cui said. The extra headspace in the bucket decreases the amount of water splashing out along the way. In similar fashion, deactivating more lithium ions during SEI formation frees up headspace in the positive electrode and allows the electrode to cycle in a more efficient way, improving subsequent performance.
There are articles that appear here and elsewhere semi-frequently about how doing something simple extends battery lifetimes a huge amount, but those never get implemented in practice except perhaps for highly niche applications.
Instead what usually happens is they'll then find a way to make them last the same amount of time, but with higher energy density. The "high voltage" lion cells (>4.2V end of charge) are an example of that process; they will last much longer than previous types if charged to 4.2V, but they'd rather advertise them as 4.3 or 4.35 or even 4.4V(!) and the extra capacity that gives.
This finding, however, specifically integrates with existing infrastructure; no new, unproven technology is needed, we just simply juice the batteries more during initial charge. If it pans out after extensive testing, we can see this technique hitting the market within 2 years.
This is a lazy dismissal of any process or efficiency improvements.
If buyers care to pay for efficiency improvements, products with them will be more attractive to them. If they don't, they won't.
If your theory were true, we wouldn't have things like rechargeable batteries, low-energy appliances, or light bulbs that would last more than two months.
There's always some performance point when most people largely stop differentiating products based on efficiency or longevity improvements, and I'm not sure if consumer Li-I batteries are at that point yet.
Read up on the Phoebus Cartel, and more recently how LED lamps which were supposed to last "almost forever" when the technology was first introduced have not lived up to expectations at all. Also, unlike incandescents, LED lamps can last much longer and be more efficient, but they are deliberately made not to --- with some very narrow exceptions: https://news.ycombinator.com/item?id=27093793
I suspect they outlive me at this point.
That's only true under monopoly conditions.
Fortunately, in capitalism, when there are two more more companies doing things like making phones, those companies actually compete on features. And battery longevity is absolutely a feature consumers care about.
And there's certainly no kind of monopoly conditions in cell phones. Competition is thriving. As it is in most types of portable electronics generally -- Bluetooth speakers, laptops, and so forth.
If you're the company that does it first, that means increased profits because suddenly more people buy your product. And if you're the company that does it last, it means decreased profits because less people will buy your product compared to the competition. That's the invisible hand at work.
I'm not into Apple, but I guess that if Apple could have chosen between that "lowering performance on iPhones when the battery capacity was decreased" shit and "precondition the cells to make them last longer", they would have chosen the second and make it very public.
If there's a capacity tradeoff, why not use a slightly modified chemistry (like how LTO is, for example)? Though I guess this article was more about the existence of the phenomenon rather than using it.
'risking it for the biscuit"
If discovery slows down capacity degradation, but now your EV battery is 100x more likely spontaneously fail ($$$) - it's not really an improvement. Maybe ok for consumer device tho.
Modern Tesla's show fairly similar long-tail degradation that is nearly identical for cars that strictly home charge and those that only supercharge (based on customer vehicle tracking). Most will level off at 85-90% of original capacity.
2021: low frequency pulsed charging: https://vbn.aau.dk/ws/portalfiles/portal/451327786/C5.pdf
2024: high frequency pulsed charging https://onlinelibrary.wiley.com/doi/10.1002/aenm.202400190
Not up to really reading them right now, but this is a pretty neat area of research!
Regardless of whether this is a "process tweak" or something "truly fundamental", a 50% increase in battery lifespan would be huge, regardless.
The conspiracy theorist in me though thinks that a lot of consumer electronics makers wouldn't like this, because lower battery capacity has to be a big driver of upgrade cycles. I'm guessing a lot of folks are similar to me: these days, somewhere in the 2-3 year mark my cell battery capacity starts degrading noticeably. My phone otherwise works great, and I certainly don't need the features in the latest model phone, and of course I know I can pay for just a battery replacement, but sometimes I think "Well, if I need to replace the battery, I might as well get a new phone - it's got <some feature that is marginally better but that I'm now convincing myself is super cool to justify my not-really-necessary upgrade purchase>".
I think with 50% more battery lifespan I would rarely, if ever, use dwindling battery capacity as an excuse for an upgrade purchase.
That is, if the results will be reproduced. I'm very skeptic about battery news.
Biggest things is that 20% degradation in a cell phone means it can't survive a whole day; whereas that difference isn't that noticeable in a vehicle, where you're not running it to 0 anyway, just charging when needed.
What nice things can you do if you take 130% longevity and something else?
That's great that you use it as an excuse to get a new phone, but whatever small percentage of people wind up being motivated to upgrade specifically because their battery doesn't hold enough charge, then gets outweighed by people who will buy one phone over another specifically because it's supposed to maintain its capacity for more years. Capitalism at work.
Re: consumer electronics, the obvious big example is cell phones, and notably major manufacturers have started adding features to extend battery lifespan by capping charge levels. Samsung has had this for a few years, originally capped at 85% but changed in a recent update down to 80%. I believe this occurred around the same time they extended their software support to 5 years. Apple added the same thing in iOS 17 with the iPhone 15 models, but despite obviously having the hardware capability ("optimized charging") they didn't enable the feature on earlier models.
At naive face value, "just" adding an extra 30% capacity to offset expected lithium deactivation implies proportional increases in material COGS and package mass/volume, all other factors being equal.
Unless (a) a manufacturer is optimizing for throughput; (b) production is constrained at this initial charge stage; and (c) supply substantially lags demand; this strikes me as a non-starter in most of the consumer space.
On a normalized basis, if current practice yields 91% finished capacity (i.e. 9% deactivation loss), and the new proposed process is expected to yield 70% finished capacity (i.e. 30% deactivation loss), then the question is how much initial material must the new proposed process start with to end with the equivalent finished capacity as the current practice?
FinCap = InitCap * (1 - DeactivationRate)
0.91
0.91 = InitCap * 0.70 --> InitCap = ---- = 1.30
0.70There's a specialized version of this called BC/RL for battery research as well.
This particular article sits about half way the scale. This was an actual study, with actual batteries, that reportedly actually had improved life spans. So dismissing that with a hand wavy this is all just academic nonsense doesn't quite fly here. But of course from here to production is indeed quite a journey. I bet a lot of companies with active investment in battery R&D are paying attention and might be going to try to replicate the success.
Also worth noting that if you only pay attention to the stuff that is at the highest levels, you basically miss out on new things until they are old news. For example if you have been dismissing solid state batteries, you might have missed the news that they are being used in products now.
Faster than what?
It turns out this is about the very first charge after assembly of the cell, not regular use.
However, I doubt that this finding will be used much, except perhaps in applications like aerospace; it is in manufacturer's economic interests that their products have short lives.
Edit: looks like as usual, comments that expose the truth get buried ;-)
> giving batteries this first charge at unusually high currents increased their average lifespan by 50% while decreasing the initial charging time from 10 hours to just 20 minutes.
That's insane
What is surprising about this research is that one small process change (doing that initial charge with a high current instead of a low one) resulted in a 50% increase in the total lifetime of the battery. That's the part that feels like "free money" in that, if accurate, this means battery producers could produce batteries with much longer lifespans without any fundamental change to their battery architecture or chemistry.
They don't exist in a vacuum, and batteries are a commodity market. Cheap ways to improve their product seem like an easy win to me.
Demand for batteries is virtually insatiable. The only constraint is the price, and a better quality product can command a higher price.
That's not true for passenger vehicles, particularly for high-spec products sold in the West. Integration of components such a battery cells that have many critical performance parameters is not trivial and manufacturers are not free to substitute cells from commodity markets. EV manufacturers are either making their own battery cells to their own, proprietary standards, or they secure contracts with suppliers capable of making cells with consistent performance. Any change in cell characteristics, including supposed improvements such as the one appearing in this report, must be integrated by the manufacturer and supply must be assured.
It's not really a commodity market, despite appearances and hype.