Half charging lithium ion batteries for longer life expectancy - Page 1
Forum section: electronics / general

author: jonovid
author_rank: Super Contributor
timestamp: May 26, 2022, 07:44:57 am
content: battery half charging and battery life expectancywhy is it that electric vehicles can have a battery life expectancy of over 10 years or more!but most call phones , e-bikes and other electronic appliances that use the same lithium ion batteries have a battery life expectancy only 2 or 3 years.can half charging lithium ion batteries for longer life expectancy work on call phones and other electronic appliances too?how would you do this? in a charger design. add a timer? if you know the full charge time.

author: tom66
author_rank: Super Contributor
timestamp: May 26, 2022, 09:30:01 am
content: Both my laptop and smart-watch can limit the peak state of charge to increase battery lifetime. In the case of the watch, it charges overnight to 75%, then predicts you will use it just before getting up, so it finishes off the charge to 100%.My impression is that Li-Ion battery life is just naturally improving anyway. I had a 6 year old iPhone at one point which would easily do over a day on a full charge and the internal diagnostics indicated it was at 90% health. Similarly, the battery in my PHEV has a good remaining lifespan, at least 95% original capacity left since 3 years past when it was replaced (recall due to water ingress, not cell failure).

author: jogri
author_rank: Frequent Contributor
timestamp: May 26, 2022, 09:30:27 am
content: There's a lot more to unpack here...-electric cars use a different cell chemistry for their battery packs (compared to mobile devices) that boasts a higher cycle count (number of times you can charge/discharge the battery before it's "dead" due to a drastically lower capacity)-phones and mobile devices are designed to have the highest volumetric energy density possible (so you can use smaller batteries), while that's not as important for cars. And you don't really need a battery with a life expectancy of 10 years for a smartphone because no one is going to use it that long -> better to use something with a higher initial capacity as something that will outlast the rest of the phone three times over-car batteries never get charged to 100 % capacity: That shortens the lifetime of the cells, so the battery managment system always keeps them between 20-80 % to ensure a longer life-most cars have "additional" batteries: If you buy a car with let's say 45 kWh chances are the manufacturer installed something like 50-55 kWh to counter the decreased capacity a few years down the road -> you observe that the range stays the same while the car had to compensate for a loss of range by using additional batteriesSo TLDR: keep your batteries between 20-80% if you want them to last longer and refrain from fast charging and discharging

author: Siwastaja
author_rank: Super Contributor
timestamp: May 26, 2022, 10:24:11 am
content: Cell phones, ebikes etc. do not fundamentally make the batteries last for just 2-3 years. Whenever this happens, it's either because the manufacturer bought lowest tier crap cells, or somehow failed the battery system design.EV manufacturers use decent quality cell, even if the same chemistry.

author: ebastler
author_rank: Super Contributor
timestamp: May 28, 2022, 09:54:42 am
content: Quote from: jogri on May 26, 2022, 09:30:27 amIs that so? First time I read this; would you have a reference? Thanks!

author: Microdoser
author_rank: Frequent Contributor
timestamp: May 28, 2022, 10:51:09 am
content: Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life, so if you charge to 4V, you will get four times the amount of charge/discharge cycles.If your project uses large numbers of charge/discharge cycles but does not use the full battery capacity, undervolting will greatly increase the working life of your batteries.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 28, 2022, 07:43:46 pm
content: Quote from: Siwastaja on May 26, 2022, 10:24:11 amUh, yeah. Sure. There are just things that are impossible to design much better in such tiny volumes. That's all. Just taking a look at Varta Li-ion batteries, which are not exactly crap, let's compare say, the 2P/LIC 18650-26 battery (19 Wh) and the Easy Blade 24 (1502 Wh), meant for electric vehicles and other industrial uses. The former has a cycle life of 300 cycles ≥ 80 %, the latter 1,200 cycles ≥ 80 %, 4 times the cycle life expectancy.300 cycles is pretty typical for the kind of LiPo batteries used in cell phones and other small mobile devices. Of course that figure doesn't mean "dead after 300 cycles", it means it still has at least 80% of initial capacity (so possibly as low as this), but what happens for say double the cycles is almost never stated, and often not that pretty in practice. Just the above figures show that the chunky industrial battery packs have a much higher cycle life.I don't know enough about battery design to fully understand where the differences lie, but I know for a fact, from experience and from tens of datasheets that the small pouch LiPo batteries have a much lower cycle life in general than the large battery packs used in EVs and for large industrial power supplies. And, for the former, not just with the "crap" ones, but pretty much all of them.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 29, 2022, 02:34:09 pm
content: I have measured some of those "300 cycle" cells and they perform way better.I guess they just leave some leeway for process variance, i.e., don't want to guarantee more than 300 cycles.On the other hand, exotic cells that are guaranteed to very large cycle ratings (LFP and LTO chemistries; thousands or tens of thousands of cycles) have the tendency of underperforming when the manufacturer is too eager to market their fancy product and do not understand all the aging mechanisms involved.Unsurprisingly, the optimal case is to use cheap enough mass technology, but commit to buy in hunderds of millions $, then work in close cooperation with the manufacturer to find how that 300 cycles can be made 1500 cycles without significant or expensive changes in the product. This is what all the EV manufacturers are doing. No magical special EV chemistries, but notexactlythe consumer cell product lines either.Tesla started with bog-standard off-the-shelf consumer cells in Roadster, IIRC. That was revolutionary; others were working with battery manufacturers too early with too little budget. Time was not ripe for that kind of cooperation or "custom EV chemistries" then. Using COTS consumer cells first was a bold move but the right one. Then Tesla went on and started to refine the process, so the cells stopped to beingexactsame consumer cells, but were still very close. For example, Panasonic NCR18650B for the early Model S, IIRC, where the major modification was the removal of PTC cap but there could have been other minor modifications as well; if nothing else, more careful screening.

author: madires
author_rank: Super Contributor
timestamp: May 29, 2022, 02:59:45 pm
content: Yesterday I've read an interview with a Varta product manager. He told that each Li-Ion cell is a tradeoff between Ah and charge cycles. In a mobile phone the cells are optimized for Ah, and in a car for charge cycles.

author: ConKbot
author_rank: Super Contributor
timestamp: May 29, 2022, 05:20:13 pm
content: Quote from: madires on May 29, 2022, 02:59:45 pmYep, the battery manufacturers have quite a few tuning knobs to adjust during cell design to get different resulting cells. Even "high quality" cells meant for hobbyist drone/RC applications have an appallingly bad service life. A coworker of mine at work handles drone stuff on occasion. He is obsessive over discharging packs to storage voltages within a few hours of wrapping up the days activities, because letting them sit at 4.2v/cell for a week or two will start to puff them pretty bad. And with the high discharges, even after a few dozen cycles, they start to get at least a bit of puff.The manufacturers have tuned these cells for 1)high rate discharge capacity. 2) low cost. 3) storage capacity. Nowhere on their priority list is cycle life, or ability to be stored full. If a consumer goes out flying on weekends, a battery that lasts 100 cycles lasted long enough.I would expect a consumer drone (dji,etc ...) Would have a better service life as they have a well characterized load, the battery ampacity is good enough, and consumers would expect it to be power-tool like. But the hobbyists with a custom build, uncharacterized load, and just want more amps for cheap take that hit in cycle life as a hidden cost.And for a 3rd type of high current battery, power tool batteries have to have a lot of amps, runtime, and cycle life, so the cost creeps up.

author: tooki
author_rank: Super Contributor
timestamp: May 29, 2022, 05:58:03 pm
content: Quote from: jonovid on May 26, 2022, 07:44:57 amFYI, this is not how you would go about it. Lithium cells are far too fickle to charge properly with just a simple timer cut-off, so you need much more advanced charge termination detection and state of charge detection. Devices that do it properly, which includes every phone, tablet, laptop, car, etc., accomplish this with dedicated ICs for both charging and state of charge monitoring. The latter are commonly called “fuel gauge” ICs, and they do it by actually counting coulombs flowing in and out of the battery, and adapt constantly to account for cell wear. (And they must be configured by the device manufacturer to calibrate them for the load.) So you would use the state of charge data from the fuel gauge IC to decide when to stop charging early.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 29, 2022, 06:07:39 pm
content: Quote from: ConKbot on May 29, 2022, 05:20:13 pmOh, but that whole market is lowest tier crap.Just flashy marketing.

author: tom66
author_rank: Super Contributor
timestamp: May 29, 2022, 06:20:21 pm
content: A key property for Li-ion battery lifespan is high coulombic efficiency.You will find many phone batteries, RC car batteries etc. get quite warm under charge, indicating relatively high loss. But, even if you cooled the cell down so that it is still at room temperature, it will deteriorate. It is not the heat that is damaging the cell, but the cause of the heat.

author: David Hess
author_rank: Super Contributor
timestamp: May 30, 2022, 12:15:05 am
content: Quote from: tom66 on May 26, 2022, 09:30:01 amMy experience is that while base battery life may be improving, consumer grade equipment charges the cells to a higher maximum capacity limiting cell life to not much more than a year.

author: james_s
author_rank: Super Contributor
timestamp: May 30, 2022, 02:45:36 am
content: Seems I read that for most Li-ion chemistries charging to 80% is optimal for long life. Temperature also plays into this, the absolute worst case for them is fully charged to 100% and elevated temperature.

author: Foxxz
author_rank: Regular Contributor
timestamp: May 30, 2022, 03:17:07 am
content: I have a pixel 6 phone that uses the alarm clock to guage how fast it should charge. If you have an alarm for no later than 10am and you plug it in in the evening it will charge and stop at 80%. Then about 2 hours before the alarm it will slowly bring the battery up to 100%

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 30, 2022, 10:34:20 am
content: I do not use my phone much and the battery lasts somewhere between 12 to 16 days.Sometimes I forget to charge it, then it turns itself off and it can sit there for a month or so.I'm guessing it's about 7 years old now and it still works as intended. Battery capacity is better then when new (apparently it has to go through 5 to 10 cycles before it reaches maximum capacity)I would have liked a bigger battery. Say a phone that's 5mm thicker and a battery that lasts a month or 2, or at least 4 days when GPS (& OsmAnd) is on, but nobody makes such phones so I have to drag power banks around when I go hiking. Those phones are all the same thin flimsy things, except maybe for some extremely expensive "ruggedized" models, which also have a short battery life.I also do not understand why people spend EUR1000 on a phone. My EUR 160 Phone works just fine. (It's got a big Mc'Donalds "M" on it's case. Is that a brandname?)I also read (a long time ago) you can "optimize" battery capacity for charge cycles by increasing the charge voltage. 4.2V gives more capacity for reduced charge cycles, and phone companies like both, while cutoff at 4.1V gives a bit (10% or so?) lower capacity, but many more charge cycles. But there are apparently a lot of different Li-Ion chemistries and this may not be true for all those variants. But for me, the battery is still good after all those years so I can't complain.I also do not understand the whining about the non-replacable batteries. If it needs replacement I'll just mill out the back of the phone and put in a bunch of 18650's and cover it with hot snot to make it waterproof again.

author: ebastler
author_rank: Super Contributor
timestamp: May 30, 2022, 11:43:22 am
content: Quote from: Doctorandus_P on May 30, 2022, 10:34:20 amMotorola? You might have come across them, they have dabbled in electronics.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 30, 2022, 04:01:37 pm
content: Quote from: Doctorandus_P on May 30, 2022, 10:34:20 amIs 13.2Ah big enough?QuoteThere's an app for that, if your device supports it:https://f-droid.org/en/packages/mattecarra.accapp/

author: Miyuki
author_rank: Frequent Contributor
timestamp: May 30, 2022, 06:13:25 pm
content: Temperature plays a huge role hereAs the electrolyte is highly volatile and with limited stability at elevated temperaturesYou can clearly see it on some EVs without proper cell temperature management, they have only limited lifeIt is a really narrow range when you can safely charge it without causing degradationYou want to keep them like 10-30*CPhones and laptops can get really hotEven storage at elevated temperatures shortens life significantly

author: Siwastaja
author_rank: Super Contributor
timestamp: May 31, 2022, 06:57:10 pm
content: Quote from: Miyuki on May 30, 2022, 06:13:25 pmThis. Basically, you would want like +30degC during use, and as cold as possible during non-use. Low-ish discharge current, or very low charging current counts as non-use.But the problem with smart phones is, they are "in use" most of the time, either discharging or charging, and only rarely is charge/discharge current insignificant or zero.They heat up and might be always at temperatures optimal for battery charge/discharge, sometimes a tad over the optimal, but never optimal for storage.But, storage degradation is something that happens all the time, even during use. And it's accelerated by high temperature. Combination of high state-of-charge and high temperature is the worst. Dropping from 100% to 80% might not help as much as people expect. Go to 60% and below for best lifetime increase.And for products that have distinct and long non-use periods, you can even store the batteries in refrigerator or freezer. Or just at 30-50% SoC. Either gives very long storage life, possibly 10 years. Combined - who knows how long. There might be some special wear-out mechanisms that step into picture after 10-20 years, that we normally don't see.

author: james_s
author_rank: Super Contributor
timestamp: May 31, 2022, 11:03:01 pm
content: Quote from: Siwastaja on May 31, 2022, 06:57:10 pmI have quite a few LiPo packs for my RC airplanes and other toys. During the off season when I'm not using them I use the charger to get them to ~50% state of charge for storage and then I store them in a drawer in my refrigerator. Many of these packs I bought in 2014 and have flown hundreds of cycles and they are still in good shape despite the fact that I have almost always charged them rather rapidly at 4C. I know other guys that aren't as diligent that burn through batteries like crazy, they puff up and/or lose capacity.