Are you killing your lithium batteries?

Discussion in 'Electric Motorcycles' started by voltsxamps, May 27, 2018.

  1. voltsxamps

    voltsxamps Advolturer

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    Are you killing your lithium batteries?
    Micah Toll

    - May. 4th 2018 9:44 am ET

    Lithium-ion batteries are expensive, and large battery packs such as those in everything from electric cars to electric motorcycles and e-bikes usually make up the single largest cost of the entire vehicle. So it makes sense that you’d want to ensure your batteries live as long and happy a life as possible.

    In order to understand how to increase the life of lithium-ion batteries, we first have to understand why they die. The short answer is that basically, during every charge and discharge cycle, very small parasitic reactions occur between the electrolyte and the electrodes inside a lithium-ion battery cell, building up over time and reducing the amount of energy the cell can both store and output.

    This is of course a seriously over-simplified explanation, but it’s enough for now, as we just want to know how to avoid this parasitic reaction, or at least slow it down in order to keep the battery alive for as long as possible.

    If you want to learn more specifics about the death process of lithium-ion battery cells, I highly recommend watching Professor Jeff Dahn’s lecture on the subject. Jeff Dahn is the leader of Tesla’s battery research partnership with Dalhousie University, and his student protegé now leads Tesla’s battery longevity program. His lecture is over one hour-long, but is well worth it if you’re a battery nerd like me.

    What causes these parasitic reactions to kill lithium-ion batteries?
    There are basically two main factors that speed up the inevitable death of your battery:

    • High temperatures
    • Increased time spent at high voltages (i.e. high charge level)
    Both of these contribute to faster death of lithium-ion batteries. According to Jeff Dahn, high temperatures aggravate the parasitic reactions that occur in a lithium-ion battery’s electrolyte, while high charge levels result in extra performance for a few cycles, followed by a crash in performance and much faster deterioration of the cell.

    Fortunately for us, both of these factors can be controlled to make batteries last as long as possible. The following simple steps can be taken to drastically increase the life of nearly any lithium-ion batteries.

    How to make Li-ion batteries last longer
    The first thing you should do is to avoid letting your battery get hot. Fortunately, many electric vehicles go part of the way there. Tesla’s vehicles and the Chevy Bolt/Volt all use active cooling to keep the battery from overheating, though the Nissan Leaf relies on passive air cooling to keep the battery cool, making battery heat an even larger factor for those vehicles.

    The bigger heat issue that you have more control over is heat during charging. Even for cars with active battery cooling, the battery still heats up considerably during charging, especially when charging at high rates or supercharging. While supercharging is convenient when you need to get back on the road quickly, it is terrible for battery life if performed often. To make your battery last as long as possible, you should try to charge at lower rates, which keeps the battery cooler and happier. A longer charge each night is much better than supercharging over lunch each day.

    Next, you should aim to charge to lower levels when possible, especially if the car will be resting for a long period of time. While it may be comforting to see your battery meter read “100%”, your battery will be anything but comfortable.

    Jeff Dahn states that charging to a level below 100% can have a large impact by reducing the rate of degradation of the battery.

    [​IMG]

    Most people don’t use their entire electric vehicle battery pack capacity every day, and rarely have the need to charge all the way to 100%. By charging a lithium-ion battery to 80%, the lifetime of the battery can be as much as doubled.

    It is important to note that the most damage from high charge levels comes from when the battery rests at such high levels for long periods of time.

    But 100% charging isn’t a big deal in small doses. If you are planning a long trip and will be heading out shortly after you finish charging, a 100% charge will have very little impact on your battery’s lifespan. However, if you will be leaving your battery unused for many days or weeks, a charge level of between 30-60% is much healthier for the batteries over the long-term.

    Does this apply to all lithium batteries?
    Theoretically yes, though LiFePO4 batteries aren’t quite as affected by high charge levels as the rest of the lithium-ion lineup. But generally speaking, these rules apply to all lithium-ion batteries from your electric car to your cell phone and even your electric tooth brush.

    For the most part, these simple methods can greatly increase the lifespan of your battery, and are easy to implement. Avoid supercharging your EV unless necessary. Park your e-bike in the shade when available. Don’t leave your laptop and phone sitting in the sun or your hot car, and avoid charging your lithium-ion battery powered devices to 100% if possible.


    https://electrek.co/2018/05/04/are-you-killing-your-lithium-batteries/
    #1
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  2. chasbmw

    chasbmw Long timer

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    As I understand it, Both Tesla and BMW limit the charging of their batteries to 80% anyway and most of this stuff is done for you if your vehicle has a half decent BMS.




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  3. longslowdistance

    longslowdistance Long timer Supporter

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    And Zero uses about 85+%. I don't know if it's the middle 85% or something different.
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  4. ex250mike

    ex250mike Long timer

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    Every time I buy something with a lithium battery I wonder what charge level it sits at. I have phones, tablets etc as well as drills, trimmers, saws all lithium powered. The batteries often cost more than the tools.

    I take good care of my RC batteries with a programmable charger. Everything else I'm stuck with the manufacturers charger.
    #4
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  5. KMC1

    KMC1 There is no spoon.

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    This is an awesome thread.
    I have 2 questions:

    What is considered to be "high temperature"?

    If I understand correctly, charging to 100% is OK as long as the charge will be used soon. How long is "soon"? I suspect there would be a ratio based on the capacity of the battery, etc.?
    #5
  6. abhibeckert

    abhibeckert Long timer

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    There's nothing you can do to prevent them from being damaged, just accept they will not last forever. Ask how long they're expected to last and try to buy from someone who's prepared to replace anything that doesn't meet that promise (even the best batteries have defects that are impossible to detect until the battery has been used for a while).

    If they're not prepared to make any guarantees... then maybe you should buy a different product. A company is supposed to do rigorous testing for safety reasons, so if they don't understand exactly how the battery performs they might also not understand how safe it is (improperly draining or charging a lithium battery is as dangerous as throwing a lit match into a tank of gas - there will be a fire, and battery fires are worse than petrol fires).

    As part of mandatory safety precautions, all lithium batteries keep a record of how many charge cycles they've gone through and what condition they're currently in (a 100Ah that has been drained half way, then charged fully, then drained half way, then charged, has gone through "one cycle").

    Unfortunately there isn't always any way to access the current cycle count or maximum capacity. You can with an iPhone for example, and mine has done 406 cycles since I bought it over a year ago and this has damaged it so it only holds 86% of the charge it had when it was new. If you know where to look on Apple's website, they say you should expect it to hold 80% of it's original capacity after 500 cycles, so mine is lasting longer than promised by the manufacturer.

    Some batteries (especially larger ones) will be more like 1000 cycles before being reduced to 80%. However it's highly dependant on temperatures your charge/drain usage pattern. You will never get exactly the cycle count they promise.



    The ideal temperature is about 20C, or 70F. Even at this temperature, they'll still be damaged but for every degree cooler or warmer the damage is worse. Batteries also naturally heat up while being used, so even if they air temperature is ideal the battery is likely to be quite a bit hotter. High power draws or fast charging heats them up more than light power draw or slow charging, so keep that in mind (maybe don't use a fast charger if you're happy going to leave it plugged in overnight anyway).

    At extreme temperatures, most batteries will turn themselves off. It's supposed to be impossible to operate any lithium battery at dangerous temperatures.

    50% is the ideal charge level for a lithium battery. Anything more or less isn't ideal, the further away from 50% the faster the battery will degrade. If your battery is going to sit in storage unused for a long time, charge it to around half full.

    Keep in mind "0%" and "100%" on the charge status indicator almost never means it's actually "empty" or "full". Often they do weird things like say it's "100%" when actually it's actively cycling up 95% then down to 90% then back up again (this is better for the battery than leaving it stationary at 90%).

    Nearly all batteries are programmed to shut down before they go completely flat and stop accepting power before they're completely full. It's entirely up to the manufacturer to decide how to calibrate this stuff. And the best approaches are quite expensive. Go for reputable brands if possible.
    #6
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  7. EvrythingAwesom

    EvrythingAwesom Long timer

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    from Endless Sphere: do not charge Lithium is the battery pack is colder than 6 Celcius.
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  8. beemerphile

    beemerphile Unreconstructed Southerner Supporter

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    TMI for me. I am just going to hope that the guys who designed my EarthX BMS and Optimate Lithium charger know all that.
    #8
  9. StuInFH

    StuInFH Been here awhile

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    Very interesting. I've been using liths in motos for over ten years, but only have had them in my RV for a year. Two Battle Born 100 Ah LiFePO4 .

    "Does this apply to all lithium batteries?
    Theoretically yes, though LiFePO4 batteries aren’t quite as affected by high charge levels as the rest of the lithium-ion lineup. But generally speaking, these rules apply to all lithium-ion batteries from your electric car to your cell phone and even your electric tooth brush."

    Been following discussions on the RV and Solar/RV boards for a number of years now. Have never seen anyone bring this up, in fact, it is all about the new chargers or how to modify the traditional multi-stage chargers to stay in Boost to get them to 100% soonest and easiest. Various manufacturers of the RV chargers for liths are all about getting to 100%, including the one I use that told me the hack to keep it in Boost instead of having it maybe cut off before.

    What is the meaning of the "aren't quite as affected" disclaimer for the Iron Phosphates? Because even if the effect is minor, there is no reason for us RVers to be striving for 100% if it is costing us. I'd rather add another batt for capacity and keep them at a lower SOC and save in the long run.

    Thoughts?
    thanks
    #9
  10. FredRydr

    FredRydr Danger: Keep Back 300 Ft.

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    I linked this thread from the CPAP users thread. CPAPs are medical devices for people who suffer from sleep apnea, the bain of motorcycle campers far from mains power!

    Some (if not most) proprietary CPAP lithium-ion batteries have no built-in means of showing the remaining charge (e.g., Transcend CPAP). Is there a device similar to a common battery tester that can be bought to (1) aid in monitoring these expensive batteries while in storage, and (2) show how much capacity the battery can only charge anymore? It's probably too late for me; I've charged my Transcend one-night battery to max a few times a year while in storage. :-(
    #10
  11. chasbmw

    chasbmw Long timer

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    Tesla and BMW EV cars have a pretty sophisticated BAttery management systems which uses active heating and cooling as needed to extend the life of the battery. Tesla is claiming that their batteries should last many more miles than the economic life of conventional cars


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    #11
  12. StuInFH

    StuInFH Been here awhile

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    #12
  13. StuInFH

    StuInFH Been here awhile

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    Would take me a minute to set alarm at 50% and a few bucks to install a charge cut off or the batt manufacturer to set cutoff at 50% in BMS or the charger manufacturer to set cutoff at 50%.
    They don't.
    I'm guessing the answer why not is the projected life, even at "only" 85% is like 20 years of use in RV scenarios.
    Considering new development and lower costs always coming along, not to mention newer rigs and me aging out of traveling, the number of cycles, even at the most conservative of estimates is plenty. Overkill even.
    Reserve capacity is our primary goal.
    Guess I answered my question myself.
    #13
  14. Lesharoturbo

    Lesharoturbo Nerdly Adventurer

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    Heat is a much bigger problem than charging .As mentioned above, most battery pack manufacturers take into account the damage of overcharging and discharging. Most do not really regulate temperature, only try to cool the batteries.
    #14
  15. ctromley

    ctromley Long timer

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    Back in the hobbyist days, lead acid was the only game in town. Range was already short and it dropped way off as temps dipped to freezing and below. It's not hard to fix. Just lining your pack with 1" of styrofoam was a big help if you drove regularly (completely sufficient for many), since driving and charging both develop heat which you could then retain. For really cold temps and/or infrequent use it was easy to install battery heaters. These were either Kapton film or nichrome wire on a heat-resistant substrate (I still have some of these). They are fairly low wattage heaters because you don't need much, so they have little effect on charging rate. Or you could wire them to operate only when charging was done and you were still plugged in. If you wanted to get fancy you could wire them up to be switchable between 120 and 240 V and turn them on and off automatically with a thermostat.

    Cold temps affect lithium too, just not as much. As trivial and cheap as this would be for OEMs to do, I think you're right that most don't. I only have a vague recollection of maybe one having it as an option. Don't remember who.
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  16. Lesharoturbo

    Lesharoturbo Nerdly Adventurer

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    With lithium, it is heat that is the killer .Life drops drastically at anything over 70f, where most companies rate their cycle life . A battery that is rated for 5000 cycles by the manufacturers may one last 3000 at 100f and only 1500 at 122f. Remember, these are battery temps, not ambient (air). Cold is bad also especially below freezing.

    My company uses a series of passive components to buffer the heat and expel it in the summer, while also being able to retain heat in the winter. It is designed mainly for lithium chemistries.
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  17. ctromley

    ctromley Long timer

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    It's important not to be too general here. It's not the 'lithium' part of the battery that's the problem, it's the other elements in the electrodes and the electro-chemical processes they go through during normal use. For example, the early Nissan Leafs (with lithium manganese batteries, IIRC?) had life issues in hot states like Arizona. They fixed that with a different battery chemistry and by the looks of things it worked. This tweaking that the material scientists and electro-chemists are doing is continuous, and can make generalizations worse than useless. Batteries are advancing faster than field experience can verify.

    Just about the time things settle down in the lithium batteries in formats we currently recognize, solid state batteries will start their own rapid and chaotic path of refinement and the whole 'obsolete rule of thumb' cycle will begin again. And then again for lithium-air, or proton batteries, or, or, or....

    Isn't this fun?
    #17
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  18. Lesharoturbo

    Lesharoturbo Nerdly Adventurer

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    Yes, there have been improvements, but the temperature issue is real. It is real for all chemistries, lead, nickel, lithium, etc. Heat is bad according to my battery engineer.

    Thermal management is critical for best battery life and performance.
    #18
  19. Andrew

    Andrew Optimus Primer Super Moderator Super Supporter

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    What's state of the art for battery cooling on electric motorcycles? I was reading MCN reviews on the Zeroes they've tested, and they definitely become sad in the pants when ridden hard and batteries overheat. Could there not be a reasonably lightweight radiator and coolant solution?
    #19
  20. Lesharoturbo

    Lesharoturbo Nerdly Adventurer

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    That is what Tesla does, liquid cooling. It is effective, but can be problematic as the coolant can damage the batteries.

    There are other ways to maintain the the temperature like heat sinks, etc. I can't say more than that due to NDAs and proprietary IP.
    #20