No one claimed that the generic storage targets are "wrong". Rather, they are nonoptiimal, and the reasons for that have been enumerated above (and have nothing to do with "someone once told me").
Looking for maintenance and care advice for Lithium ion battery pack
- Thread starter ifoxbox
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No one claimed that the generic storage targets are "wrong". Rather, they are nonoptiimal, and the reasons for that have been enumerated above (and have nothing to do with "someone once told me").
their manufactures recommend, is fine and I would trust them over Gauss
. The 3.85V storage mode on most chargers is a reasonable and well thought out value imo considering all the different conditions, storage times, and chemistries that an average user might encounter. Gauss can calculate right down to the 0.001V what is the ideal storage voltage for his particular cell and ambient temperature if he wants and he will likely see little benefit. Us normal folk have better things to do imo.[/QUOTE]
Yeah, sometimes I like to ignore the accepted science and engineering myself just to see if it blows up in my face. Otherwise you'll never have anything interesting to talk about in the locker room.
. The 3.85V storage mode on most chargers is a reasonable and well thought out value imo considering all the different conditions, storage times, and chemistries that an average user might encounter. Gauss can calculate right down to the 0.001V what is the ideal storage voltage for his particular cell and ambient temperature if he wants and he will likely see little benefit. Us normal folk have better things to do imo.[/QUOTE]Yeah, sometimes I like to ignore the accepted science and engineering myself just to see if it blows up in my face. Otherwise you'll never have anything interesting to talk about in the locker room.
Tachead
Flashlight Enthusiast
Gauss, some people leave their packs and/or 18650's at full charge all year round and still get many years and hundreds of cycles out of them at a respectable capacity. You are making it sound like if you don't keep your cells at the exact "optimum" storage level they will quickly die or explode lol. The actual difference in capacity loss/cycle life between keeping a cell at the exact "optimal" storage to the millivolt, for the chemistry and ambient temperature, or being 0.1-0.2V higher or lower is probably so small that only a person with OCD or no life would even begin to care.
And, I agree with the above poster. Your story of supposedly schmoozing with industry battery experts in Japan and South Korea holds no weight. Anyone can claim anything on the internet and your history around here doesn't exactly inspire confidence. Not too mention, the battery guys from Panasonic, Sony, and LG wouldn't exactly be experts on what other major cell manufacturers(many in other countries) have in their research and testing labs nor would they have unbiased opinions.
The other issue Gauss is you really have no idea how the chemistries of a particular lipo pack compare to the 18650's you are using as your guide. So, basing your charging practices on another cells data, when it could be completely different(and likely is), instead of the using the particular cells manufactures recommendations seams rather foolhardy if you ask me.
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Tachead
Flashlight Enthusiast
You posted while I was typing that post. I was talking about novarider's post(#40).
You agree that you should use the charging recommendations from a totally different type of cell from a different cell manufacturer over what the actual cells manufacturer recommends?:thinking:. Do you use the manual from a Chevy Volt to learn how to use your Ford F250 Powerstroke too?
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Tachead
Flashlight Enthusiast
Nice, business or pleasure? If you have a light with you that could be a good entry for the pictures of lights around the world thread.
Highly doubtful. Keeping packs at high voltages greatly accelerates internal degradation processes.
Where did you get that strange idea? Claiming that storage voltages are nonoptimal implies nothing of the sort. Ditto for the rest of the (deleted) nonsense following that.
The electrochemical processes that govern the major Li-ion battery degradation mechanisms are essentially uniform across all Li-ion chemistries. So your argument makes no sense (yet again).
Mostly pleasure, although I used a lot of the time in the evening to write a technical article I've been thinking about for a while that turned out better than I was expecting.
But getting back to the battery issues, it sounds to me like you both have a lot of knowledge about the subject. Gauss is saying many of the same things I've read here by other knowledgeable people as well as in the technical literature. I've also seen others report the same experiences in practice that you've had. Who is right? Well, I guess that depends on your point of view.
For example, a big manufacturer of batteries with global sales in the tens or hundreds of millions will obviously need to have more conservative standards and recommendations just to cover their butts and because they have deep pockets. And presumably they know their own batteries pretty well. On the other hand, a very experienced user, who knows his batteries and equipment may feel that he can push the envelope a bit without too much risk. I sometimes do the same. Just my two cents, but this seems to me to be at the crux of your disagreement. Others mileage may vary.
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Overclocker
Flashlight Enthusiast
it's funny how people mistakenly think that lipos are fundamentally different from 18650. they seem to think that lipo means lithium polymer, as being different from "lithium ion". but actually it's "lithium ion polymer". i think that's where the confusion comes from.
there was a time when you couldn't change the charge limits on laptops so they ran hot all the time at 100%. cells didn't last long. here are my settings on my ThinkPad
Part of that confusion is due to the fact that the name LiPo or lithium polymer was originally used for cells that employed polymer (vs. liquid) electrolyte, whereas nowadays it generally refers to pouch cells (with polymer casing) but liquid electrolyte (same as in 18650 cells).
But also much confusion is due to rampant misinformation on the web. This is somewhat unique and due primarily to the fact that much of the information is considered proprietary by the manufacturers so not available to the general public. This vacuum was filled by guesses, old wives tales, marketing hype, pseudoscience, etc. It is a very difficult process to correct some of these mistakes when the misinformation has propagated so widely (e.g. to sites like Battery "University" - kudos to Wikipedia for blacklisting it).
Tachead
Flashlight Enthusiast
It's proven Gauss. Many people on here leave their spare cells fully charged all the time so they are ready to use and still get several years of service out of them. Would they have gotten more if they always kept them at storage? Sure but, the difference isn't as drastic as you make it out to be. And, the difference between storing them at their ideal storage voltage(for chemistry and ambient temp) vs. 0.1-0.2V higher or lower is likely hardly even noticeable to the average user. As an example, I have a 4 year old li-ion that has been cycled hundreds of times and was left at 100% charge 8-12 hours per day every day of those 4 years. That's between 11680 and 17520 hours or around 2 years at full charge. It doesn't have the same capacity it once did(nor would any cell this old and cycled this much) but, it still works well and has plenty of capacity.
You don't even know they are "nonoptimal" and have been using data for different cells from different manufacturers to base your claims on. And, then you go on to say that we should disregard the manufacturers charging data because it is outdated and inaccurate when you have no idea or proof if that is even true. You also have no proof that Panasonic, Sony, or LG has any better testing equipment or procedures then any of these lipo manufacturers yet you claim it anyway. You make it sound like these hobby pack lipo manufacturers are just some tiny warehouse in China. One of the companies that makes many of these hobby packs is one of the top battery companies in the world, does over 150 million in battery sales annually, and has over 3000 employees. Remember, they just make batteries too unlike Panasonic, Sony, or LG.
Gauss, you have been claiming that the "optimal" storage voltage is "dependent on chemistry" all along. You even posted some charts to prove it. Now you're saying they are all the same? How does my argument not make sense? The charging data for other cells(18650's in this case) is irrelevant. The only data that matters is the data for the particular cell we are talking about because only the manufacture knows its particular cells chemistry and the best charging procedures for it. But, you are telling us we shouldn't follow the manufactures data because you(Mr expert) think it's flawed. I am sorry but, I am going to believe the manufacturer over some guy on the internet(you) who thinks they are an expert because they have read a few of HKJ's articles and can use google:shakehead.
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Which proves absolutely nothing about optimal storage voltages.
It is ridiculous how much misinformation has propagated in the RC/hobby charger world. Here's one way much misinformation has been propagated: Battery "University" picks up old-wives tales off of hobby forums and publishes them as if they were scientifically-proven facts. These dubious claims are then recycled by Chinese pack manufacturers who have little-to-no research budget so no capability to vet such claims. Some of the lower-tier hobby pack manufacturers actually explicitly refer to Battery University (as if it had some credibility).
Needless to say you'd never find such nonsense from top-tier manufacturers. Caveat Emptor. Look elsewhere for accurate information.
Tachead
Flashlight Enthusiast
You said it was "highly doubtful" I am just showing you that it is in fact quite probable and has been proven many times over by myself and other users. Furthermore, it proves that modern Li-ion/Lipo cells are very resilient and making sure that your cells are at the exact "optimal" storage voltage for all conditions at all times doesn't make a big difference for the average user. Even when abused they still offer a pretty amazing service life.
I like how you always disregard half of my posts lol.
I agree that battery university is not a good place to source your knowledge, neither is wiki, nor from a flashlight forum user who thinks he knows it all and suggests using the data from totally different cells
. It is much safer to go by the manufacturers recommendations imo. All good manufacturers include charging and storage recommendations in the literature that comes with their packs or on the packs themselves. If not, it can be found on their websites or datasheets. I'm looking at one of my hobby packs right now. It says right on the back "Store long term at 3.8V per cell." along with a bunch of other charging and usage info. Why would I ignore that and use the recommendations for a totally different cell from a different manufacturer:thinking:.We are not talking about "low tier" hobby pack manufacturers here though nor 18650's. We are talking about a $235 DJI OEM lipo. Most hobby pack manufacturers don't even make the cells, they just assemble the packs and throw a label on them. And, RC enthusiasts don't use "low tier" packs for the most part either in my experience. I personally would never risk strapping an off brand "low tier" pack to one of my multi thousand dollar helis. Not only would it be too much risk but, it likely wouldn't offer the performance and longevity I require.
Many hobby packs are made by top-tier cell manufacturers. My main supplier has over 200 engineers and technicians dedicated solely to research, development, and testing. I trust their charging recommendations and have had great performance and longevity by following them.
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If you think that the anecdotes that you posted above constitute "proof many times over" then it's no wonder you don't understand what I wrote. Report back after you have hard data from carefully controlled tests so that we can determine precisely how much life you have lost by abusing your packs by storing them fully charged.
Most hobby companies have little-to-nil expertise on such matters. They are simply passing along very rough, old rules of thumb that are far from optimal in many contexts.
Oooook. This thread is becoming a debate between just two members. OBVIOUSLY, you are not going to convince each other. You've each said your part, let's leave it there and let some other folks carry on the discussion. Thank you in advance for your cooperation.
Gauss has still not provided any proof whatsoever to his claims. Lipo batteries and 18650 batteries have very different discharge and charging capabilities and yet he still says they are the same.
"Needless to say you'd never find such nonsense from top-tier manufacturers. Caveat Emptor. Look elsewhere for accurate information"
Please provide a link where a "top-tier" lipo manufacturer says to charge their batteries lower than 3.85v for storage
"Needless to say you'd never find such nonsense from top-tier manufacturers. Caveat Emptor. Look elsewhere for accurate information"
Please provide a link where a "top-tier" lipo manufacturer says to charge their batteries lower than 3.85v for storage
SilverFox
Silver Moderator
There are some interesting ideas in this thread...
The driving question in my mind is at what discharge rate should the 50% state of charge be measured at...?
If my application is set up so I get hours of use from the battery pack, then I would review the data from Texas Instruments and the various cell manufacturers and go with their recommendations. On the other hand if my application only gives me minutes of use, my 50% level would involve higher voltages.
I recently purchased a jump pack. Its LiPo battery is advertised at a momentary maximum current of 4000 amps. Not bad for a 8 Ah battery pack.
I came across a diesel truck that had dead batteries. When I turned the key on, the dash wouldn't even respond. I hooked up the jump pack and discovered that the trucks batteries were at 1.8 volts. I hit the safety bypass on the jump pack and the voltage quickly rose to around 8 volts. I cranked a couple of times and finally the engine started. After disconnecting the jump pack and letting it cool down I checked and it was showing 75% left which corresponds to around 3.9 volts per cell from previous testing.
The next day I had to start the truck again. I hooked up the jump pack and noticed that the truck batteries were showing about 8 volts. I cranked the engine, but my pack ran out of power before the engine would start. I hit the low voltage shut off for the pack. After letting the pack cool down it was showing about 25% left in it.
At roughly 600 amps, 50% state of charge is a little more than 3.9 volts per cell. Does that indicate that the "optimum" storage voltage for me is around 3.9 volts?
I never know when my jump pack will be needed and I want to make sure it does the job when it is needed. I also want to optimize its storage for longevity. My balance is to charge it to 4.0 volts per cell. This is less than full charge but still charged enough to get the job done when it is needed. The lesson I learned is that after using it I need to charge it back up prior to the next severe use.
This thread started with a discussion about optimized storage conditions for a drone's battery pack. If 50% state of charge is the metric I suppose you could run the drone for half of its run time, let the battery cool down and recover, then measure the batteries voltage. This would give you 50% state of charge for this application.
Theoretically, theory and practice should be close to the same. However in actual practice sometimes they are quite different. My round LiIon cells are around 7 - 8 years old. I have optimally stored them at 4.0 volts. They are still working very well...
Tom
The driving question in my mind is at what discharge rate should the 50% state of charge be measured at...?
If my application is set up so I get hours of use from the battery pack, then I would review the data from Texas Instruments and the various cell manufacturers and go with their recommendations. On the other hand if my application only gives me minutes of use, my 50% level would involve higher voltages.
I recently purchased a jump pack. Its LiPo battery is advertised at a momentary maximum current of 4000 amps. Not bad for a 8 Ah battery pack.
I came across a diesel truck that had dead batteries. When I turned the key on, the dash wouldn't even respond. I hooked up the jump pack and discovered that the trucks batteries were at 1.8 volts. I hit the safety bypass on the jump pack and the voltage quickly rose to around 8 volts. I cranked a couple of times and finally the engine started. After disconnecting the jump pack and letting it cool down I checked and it was showing 75% left which corresponds to around 3.9 volts per cell from previous testing.
The next day I had to start the truck again. I hooked up the jump pack and noticed that the truck batteries were showing about 8 volts. I cranked the engine, but my pack ran out of power before the engine would start. I hit the low voltage shut off for the pack. After letting the pack cool down it was showing about 25% left in it.
At roughly 600 amps, 50% state of charge is a little more than 3.9 volts per cell. Does that indicate that the "optimum" storage voltage for me is around 3.9 volts?
I never know when my jump pack will be needed and I want to make sure it does the job when it is needed. I also want to optimize its storage for longevity. My balance is to charge it to 4.0 volts per cell. This is less than full charge but still charged enough to get the job done when it is needed. The lesson I learned is that after using it I need to charge it back up prior to the next severe use.
This thread started with a discussion about optimized storage conditions for a drone's battery pack. If 50% state of charge is the metric I suppose you could run the drone for half of its run time, let the battery cool down and recover, then measure the batteries voltage. This would give you 50% state of charge for this application.
Theoretically, theory and practice should be close to the same. However in actual practice sometimes they are quite different. My round LiIon cells are around 7 - 8 years old. I have optimally stored them at 4.0 volts. They are still working very well...
Tom
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