Why Lithium Ion Batteries Prematurely Fail
- Thread starter Joseph C.
- Start date
Interesting responses to an email to Jeff Dahn on Tesla Motors Club forum. It's Model S battery-specific but informative nonetheless.
http://www.teslamotorsclub.com/showthread.php/27109-Why-do-Li-ion-Batteries-die-And-how-to-improve-the-situation/page2?p=572297&viewfull=1#post572297
http://www.teslamotorsclub.com/showthread.php/27109-Why-do-Li-ion-Batteries-die-And-how-to-improve-the-situation/page2?p=572297&viewfull=1#post572297
dnmun
1 PW
starts out so boring, but this is a great lecture. he talks about the stuff luke talked about, reactions of the electrolyte with the negative electrode at higher voltages, and then the last question, about overhang was something i had never heard of, but it makes total sense. worth the waste of time imo.
ridethelightning
1 MW
- Joined
- Jul 21, 2013
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- 2,010
great thread! solid advice by the looks...ill be following this.
dogman dan
1 PW
Thanks for the link to an outstanding lecture. Skip to the last bit for practical advice on extending battery lifespan.
Keep it as cool and low v as possible.
Where I live, I'm screwed, and if I want to hop on and ride anytime, I'm screwed. :lol: Sure glad I couldn't afford a Leaf, it would not last in my garage very long. At least the batteries I ruin are bike size in cost.
It's worth a watch. Though a technical subject way past my level of understanding, he does such a great job on the lecture that I could understand his conclusions, even if the graphs were Sanskrit to me.
Very interesting to see why the typical spec chart on a battery cell has so little to do with how it performs on the road. In my case, the road is too hot for too much of the year. But top of charge is something I can control, so I may just use that lower setting on my charger more than I have been.
You do what you can, and figure to solve the rest of the problem with mo money next year. Works for a bike, but imagine having a car size battery crap out early on ya.
One thing never touched on in the lecture, discharge rate. But I did notice that his tests were never at anything like 1c. So there is another thing you have to wonder about. How inconsistent is the max c rate they specify, relative to the cycle life spec? Their tests, if even done at all, may not correlate because of differing temps out on the road.
One last dig on the battery manufacturers. He went on and on about the effectiveness of electrolyte additives. Three guesses which type of battery would be the one with the least additives? Could the brand name start with a Z?
Keep it as cool and low v as possible.
Where I live, I'm screwed, and if I want to hop on and ride anytime, I'm screwed. :lol: Sure glad I couldn't afford a Leaf, it would not last in my garage very long. At least the batteries I ruin are bike size in cost.
It's worth a watch. Though a technical subject way past my level of understanding, he does such a great job on the lecture that I could understand his conclusions, even if the graphs were Sanskrit to me.
Very interesting to see why the typical spec chart on a battery cell has so little to do with how it performs on the road. In my case, the road is too hot for too much of the year. But top of charge is something I can control, so I may just use that lower setting on my charger more than I have been.
You do what you can, and figure to solve the rest of the problem with mo money next year. Works for a bike, but imagine having a car size battery crap out early on ya.
One thing never touched on in the lecture, discharge rate. But I did notice that his tests were never at anything like 1c. So there is another thing you have to wonder about. How inconsistent is the max c rate they specify, relative to the cycle life spec? Their tests, if even done at all, may not correlate because of differing temps out on the road.
One last dig on the battery manufacturers. He went on and on about the effectiveness of electrolyte additives. Three guesses which type of battery would be the one with the least additives? Could the brand name start with a Z?
Ykick
1 GW
Well worth some TV time. Good stuff, thanks!
Just one of many not so obvious benefits of an eBike is that we get to "test & learn" without the large monetary investment required to play with the big stuff.
Those of us doing eBikes for a few years will have much stronger advantage when shopping EV's on showroom floors. EV car salesmen are gonna hate us, LOL....
Just one of many not so obvious benefits of an eBike is that we get to "test & learn" without the large monetary investment required to play with the big stuff.
Those of us doing eBikes for a few years will have much stronger advantage when shopping EV's on showroom floors. EV car salesmen are gonna hate us, LOL....
dogman said:
Lithium Manganese Oxide really doesn't like the high temperatures. The Leaf would be fine in places like Ireland. You'd imagine though that it would relatively easy to install a thermal management system to keep the batteries below 40 degrees C. The task should be made easier by the fact that the battery pack is quite small in comparison to a Model S.
LiFePO4 doesn't seem to be great at dealing with the high temperatures according to the graphs. Lithium NMC is actually quite good.
The Tesla NCA battery appears to be the most desired chemistry for our applications according to that. He reckons it will last decades. I'd imagine that the Samsung NCA that Cellman sells would give a pretty similar performance.
It's a pity they don't make lithium titanate on a mass scale as it would be the perfect solution for grid storage. In the video he maintains that it will last a life-time. Perhaps 50 years or so by extrapolating the probable age of the person who asked the question with the average life span.
It's all very exciting. For Endless-Sphere members we now have much better information as to what chemistries/brands are more suited for certain applications and climates.
Best chemistries for high temperatures:
Lithium Titanate > daylight > lithium NCA > followed by Lithium NMC.
Poor choices for high temperatures:
LiFePO4 > LiMnO2 (terrible choice).
Edit: Really got those chemistries wrong.
http://www.youtube.com/watch?v=pxP0Cu00sZs#t=240
nicobie
100 MW
Ykick said:
I know a couple who already don't like me and my questions that they couldn't answer.
Matt Gruber
1 MW
thanks for that email! more helpful than the video imo.
.
Not all of us live in the desert!
average in summer here 30c,85f
that is why i have an ebike, for a summer breeze.
.
maybe someday i'll change from 10s to 11s
11s will charge to 44.0v or 4.00 per cell on my old charger. battery could last for years after i die LOL
.
Not all of us live in the desert!
average in summer here 30c,85f
that is why i have an ebike, for a summer breeze.
.
maybe someday i'll change from 10s to 11s
11s will charge to 44.0v or 4.00 per cell on my old charger. battery could last for years after i die LOL
dogman dan
1 PW
I was happy to see I have the right chemistry for a hot place. But I told my wife, I'm sure I have the wrong brand. :lol:
What we need is a combination of additives that gets cycle life to 10,000 or better, and gets that at 40c. I found it encouraging that they were running a lot of the tests at 40c. That implies to me that they are looking to improve hot battery cycle life. Better still if they are working on hot battery calendar life.
But I won't hold my breath for that magic combination of additives to be offered dirt cheap from HK. In a way, they'd be stupid to make those kind of batteries last longer.
As long as I am running the cheaply made RC stuff, I just plan to replace half my capacity every year. I know by the end of year three, they will be running at half capacity regardless of cycles. I should be able to maintain 30 ah of 14s that way, with 1/3 new, 1/3 still good, 1/3 tired and only good for 50-70% capacity. Anytime I run 10 ah or less, I'll use the newest ones.
What we need is a combination of additives that gets cycle life to 10,000 or better, and gets that at 40c. I found it encouraging that they were running a lot of the tests at 40c. That implies to me that they are looking to improve hot battery cycle life. Better still if they are working on hot battery calendar life.
But I won't hold my breath for that magic combination of additives to be offered dirt cheap from HK. In a way, they'd be stupid to make those kind of batteries last longer.
As long as I am running the cheaply made RC stuff, I just plan to replace half my capacity every year. I know by the end of year three, they will be running at half capacity regardless of cycles. I should be able to maintain 30 ah of 14s that way, with 1/3 new, 1/3 still good, 1/3 tired and only good for 50-70% capacity. Anytime I run 10 ah or less, I'll use the newest ones.
Wheazel
10 kW
Fantastic lecture, thanks for posting!
Spacey
100 kW
Charging at lower voltage is better for the battery for sure, but we have to make sure that the BMS can balance at that lower voltage otherwise the pack goes out of balance pretty quick.
wesnewell
100 GW
I never bought into the life cycle of lifepo4. That's why I went with rc lipo years ago. This seems to authenticate that for warmer climates. I still charge to 4.2V though. I don't need a pack to last more than 2 years though. I can replace my 10ah 24s pack with all new cells for $275 in minutes.
e-beach
10 MW
Maybe it it time to start recharging them packs in a refrigerator! :lol:
Spacey said:
I don't think fully charging a battery does it much harm if you don't leave it topped up for long periods.
If you used it immediately I imagine the impact would be negligible.
Fully charging it regularly before using it should mean it is always balanced.
Yeah saw this a while back. Super duper great! must watch the whole thing!
Explains how mfg cheat on their spec sheets
A123 seems to have great cycle life at high temp according to the data sheet
But that is because they are charging relative fast at high temps
Also explains how Nissan fcuked up with the Leaf
Also explains additives can matter more than anything in some ways
But remember manganese sucks for ultra long calendar life
Sort of explains why nca rules (a little cobalt goes a long way)
(Aluminum never dissolve in electrolyte like manganese)
a USA lithium battery factory will make more cells in 2015 than all asian manufacturers combined in 2013
who woukd have thought :wink:
Note Tesla hired one of his students
Cant wait for the megafactory to break ground late this year
Explains how mfg cheat on their spec sheets
A123 seems to have great cycle life at high temp according to the data sheet
But that is because they are charging relative fast at high temps
Also explains how Nissan fcuked up with the Leaf
Also explains additives can matter more than anything in some ways
But remember manganese sucks for ultra long calendar life
Sort of explains why nca rules (a little cobalt goes a long way)
(Aluminum never dissolve in electrolyte like manganese)
a USA lithium battery factory will make more cells in 2015 than all asian manufacturers combined in 2013
who woukd have thought :wink:
Note Tesla hired one of his students
Cant wait for the megafactory to break ground late this year
TheBeastie
1 MW
Great video, was really interesting, don't see enough of this type of stuff out there.
So seems like some of the rules that have come up for discussion have been re-enforced by this battery professor.
Don't charge above 4.1 for maximum cycle life, I thought that slide showing dramatic death of cells that they performed the best on all counts for the first 50 cycles when charged at 4.3v then abruptly died was really interesting, while charging to a little less (4.1) appeared to give many times more life cycles.
And try to keep them as cool as possible, think I will ride with my em3ev frame bag with the zip a bit more open from now on.
I am now wondering how different NCA are from say HK Turnigy Lipo, obivously Tesla are cobalt fans and I can only assume that means NCA are a bit more flammable then boring Lifepo4 or lith-Manganese.
As far as lipo performance goes I think from looking at all the talk here on the ES forum about different HK lipo brands that Turnigy are the leaders in "secret sauce" additives as the professor like to put it for better performance.
So seems like some of the rules that have come up for discussion have been re-enforced by this battery professor.
Don't charge above 4.1 for maximum cycle life, I thought that slide showing dramatic death of cells that they performed the best on all counts for the first 50 cycles when charged at 4.3v then abruptly died was really interesting, while charging to a little less (4.1) appeared to give many times more life cycles.
And try to keep them as cool as possible, think I will ride with my em3ev frame bag with the zip a bit more open from now on.
I am now wondering how different NCA are from say HK Turnigy Lipo, obivously Tesla are cobalt fans and I can only assume that means NCA are a bit more flammable then boring Lifepo4 or lith-Manganese.
As far as lipo performance goes I think from looking at all the talk here on the ES forum about different HK lipo brands that Turnigy are the leaders in "secret sauce" additives as the professor like to put it for better performance.
dnmun
1 PW
his thesis is that the pores in the negative electrode which is finely ground graphite, carbon, are being clogged up by the growth of the SEI gunk in between the particles. he has an SEM of the surface so you can see what he was talking about. this growth is the parasitic reactions he was talking about that are faster at higher temperature and which are increased in effect by time at the same temperature. that was what he meant in showing how the graphs of the 1-CE versus charge cycle.
from what he says, it is best to just leave the battery uncharged until needed. just the opposite of what people think they should do since they are used to lead acid batteries.
time at full charge has to be minimized to reduce the total amount of these parasitic reactions which are time dependent. the longer it spends at the high voltage of the charged state then the more of these materials that are produced to clog up the pores.
the temperature is dependent on the current demand. the higher the Crate the hotter the battery so these parasitic reactions increase because the battery is hot, not because the ambient temperature is hot, which does contribute at these low Crates he uses in his experiment.
lipo discharge rates that people use are 3-4 times what he is discharging at so the ambient temp is not as important, during discharge. the temperature at charging is when the effect is greatest on these parasitic reactions as the voltage increases as the charging takes place and electrolyte potential is raised to the level that the reactions are promoted.
the stuff he talked about at the end involving the calorimeter is how they are measuring these reaction rates by measuring the heat given off in the reaction. so that is what he meant when he said this is the direction his research is going. they will use the calorimeter to evaluate the heat released in these reactions as the battery is charged to see what effect additives have on these reactions of the electrolyte with the carbon of the negative electrode.
when the negative electrode is lithium titanate then there is no carbon for these reactions to take place on so the additives have no relation then to the conditions for the carbon electrode. but the lithium titanate has about 1.03 eV potential as i recall and carbon is 0, so the cell voltage of the lico with titanate is only about 3V as i recall. so less energy can be stored. but like luke said, for a stationary power storage it is the best option because then the size and weight don't matter.
so that is why carbon is used and why people put up with the problem. he is trying to minimize the problem by identifying the mechanism that causes this problem to prematurely end the ability of the negative electrode to accept current. in the form of charged lithium ions.
edit: from this lecture the best thing people who use these lipo pouches could do is to put a timer on their charger so that the charger would turn on so it would then charge up just before the battery is needed. then you could charge to 4.2V and have as little damage perhaps as charging to 4.05V and leaving it charged all the time. all this is unknown and unquantified.
from what he says, it is best to just leave the battery uncharged until needed. just the opposite of what people think they should do since they are used to lead acid batteries.
time at full charge has to be minimized to reduce the total amount of these parasitic reactions which are time dependent. the longer it spends at the high voltage of the charged state then the more of these materials that are produced to clog up the pores.
the temperature is dependent on the current demand. the higher the Crate the hotter the battery so these parasitic reactions increase because the battery is hot, not because the ambient temperature is hot, which does contribute at these low Crates he uses in his experiment.
lipo discharge rates that people use are 3-4 times what he is discharging at so the ambient temp is not as important, during discharge. the temperature at charging is when the effect is greatest on these parasitic reactions as the voltage increases as the charging takes place and electrolyte potential is raised to the level that the reactions are promoted.
the stuff he talked about at the end involving the calorimeter is how they are measuring these reaction rates by measuring the heat given off in the reaction. so that is what he meant when he said this is the direction his research is going. they will use the calorimeter to evaluate the heat released in these reactions as the battery is charged to see what effect additives have on these reactions of the electrolyte with the carbon of the negative electrode.
when the negative electrode is lithium titanate then there is no carbon for these reactions to take place on so the additives have no relation then to the conditions for the carbon electrode. but the lithium titanate has about 1.03 eV potential as i recall and carbon is 0, so the cell voltage of the lico with titanate is only about 3V as i recall. so less energy can be stored. but like luke said, for a stationary power storage it is the best option because then the size and weight don't matter.
so that is why carbon is used and why people put up with the problem. he is trying to minimize the problem by identifying the mechanism that causes this problem to prematurely end the ability of the negative electrode to accept current. in the form of charged lithium ions.
edit: from this lecture the best thing people who use these lipo pouches could do is to put a timer on their charger so that the charger would turn on so it would then charge up just before the battery is needed. then you could charge to 4.2V and have as little damage perhaps as charging to 4.05V and leaving it charged all the time. all this is unknown and unquantified.
Spacey
100 kW
I agree with all the statements above, but here is a thought......
I have a 3 year old 12S 1P 12Ah Headway pack that I built, it has been on the charger 100% for 3 years.
It still gives out over 11.5Ah and is in constant use. In the winter not so much use at all but it is still left on the charger with the BMS keeping the pack nicely in balance. I would say it gets used 3 to 4 times a week by the company that own it.
I recently serviced the bike and did a full check on the capacity of the battery and was happily surprised that it was in such good health.
These are facts that I have from the real world.... but it seems at odds with the information we now have, leaving it on the charger at 3.65v a cell on LiFePo4 cells has not had a negative effect on this pack after 3 years?
I have a 3 year old 12S 1P 12Ah Headway pack that I built, it has been on the charger 100% for 3 years.
It still gives out over 11.5Ah and is in constant use. In the winter not so much use at all but it is still left on the charger with the BMS keeping the pack nicely in balance. I would say it gets used 3 to 4 times a week by the company that own it.
I recently serviced the bike and did a full check on the capacity of the battery and was happily surprised that it was in such good health.
These are facts that I have from the real world.... but it seems at odds with the information we now have, leaving it on the charger at 3.65v a cell on LiFePo4 cells has not had a negative effect on this pack after 3 years?
dnmun
1 PW
i wonder if headway is using something like his mystery ingredient on that one mu5 or whatever it was, versus the mu4 without the secret sauce. forgot the symbols.
in some of the first papers i read they talked about their experiment where they charged the lifepo4 cell to 4.4V to fully charge it first for the experiment and i thought that was fatal. but not for single experiments i guess.
but i have overcharged lifepo4 to 4.25 accidentally without killing it. headway 38120 though, never a ping.
maybe the total number of cycles?
in some of the first papers i read they talked about their experiment where they charged the lifepo4 cell to 4.4V to fully charge it first for the experiment and i thought that was fatal. but not for single experiments i guess.
but i have overcharged lifepo4 to 4.25 accidentally without killing it. headway 38120 though, never a ping.
maybe the total number of cycles?
Spacey
100 kW
Could be a lack of daily use, but they would have had at least 500 cycles on it by now. And they are kept on an almost trickle charger where the BMS is fed with just enough power to keep all the cells nicely and very gently topped up at 3.65v.
I had tried timers but it just was not feasible, keeping them on charge all the time all year round whether they were used or not meant that the packs were always in perfect balance.
If a pack goes out of balance from not being charged then sure.... the BMS will balance it.... but it will also take the most charged cells to over 3.8v until the slower cells catch up. This could take days on a pack out of balance by say 3Ah's.
BMS starts burning off extra power stop the charger when a cell goes over 3.65v but only stops the actual charger when a cell goes over 3.8v.
I had tried timers but it just was not feasible, keeping them on charge all the time all year round whether they were used or not meant that the packs were always in perfect balance.
If a pack goes out of balance from not being charged then sure.... the BMS will balance it.... but it will also take the most charged cells to over 3.8v until the slower cells catch up. This could take days on a pack out of balance by say 3Ah's.
BMS starts burning off extra power stop the charger when a cell goes over 3.65v but only stops the actual charger when a cell goes over 3.8v.
dogman dan
1 PW
Don't be hot and charged seems to be the golden rule.
I found pings lasted 3 summers in my horrible climate before they lost much capacity. So maybe the result you see with the headways is either taking longer because that pack is not left in a 40c garage, or it's about to go off the deep end like my pings did, at about 3.5 years.
Both Turnigy and Zippy lico have gone off the cliff for me in capacity for me in 2 years. So the lifepo4 apparently does handle hot storage a bit better.
Both types stored fully charged. I suspect less secret sauce in both brands myself. Likely headway and others use something.
The things I take from this lecture is..
Do what's practicable to minimize full charged time. If that's don't charge at all till about to ride great. But at least store less charged when you can.
Let a hot pack cool before charging. Do what's practicable to store your battery at 20c, rather than leave em in a 40c garage. If room temp is not cold enough, where do I order a china girl kit?
The lico packs I killed the fastest, were discharged deep at a c rate that got them very hot each cycle. Hotter than 40c. About 50 cycles.
I found pings lasted 3 summers in my horrible climate before they lost much capacity. So maybe the result you see with the headways is either taking longer because that pack is not left in a 40c garage, or it's about to go off the deep end like my pings did, at about 3.5 years.
Both Turnigy and Zippy lico have gone off the cliff for me in capacity for me in 2 years. So the lifepo4 apparently does handle hot storage a bit better.
Both types stored fully charged. I suspect less secret sauce in both brands myself. Likely headway and others use something.
The things I take from this lecture is..
Do what's practicable to minimize full charged time. If that's don't charge at all till about to ride great. But at least store less charged when you can.
Let a hot pack cool before charging. Do what's practicable to store your battery at 20c, rather than leave em in a 40c garage. If room temp is not cold enough, where do I order a china girl kit?
The lico packs I killed the fastest, were discharged deep at a c rate that got them very hot each cycle. Hotter than 40c. About 50 cycles.
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