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Thread: Charging Li-ion to 4.1X v

  1. #1

    Default Charging Li-ion to 4.1X v

    Undercharging of li-ion is very popular them for discussion.

    There are a lot of topics on the Internet with such words:
    "I bought a charger, it charge to 4.1x volt is it faulty?"
    "My expensive *BRAND_NAME* chargerer charge only to 4.1x. Should I send it back?"

    Is undercharging so bad?

    I have used many different chargers for the last few years. Nitecore i2, F1; Miller ML-102v8/v9; Xtar MC1, MC1 ANT, SP1; LiitoKala Lii 100. None of them charge batteries exact to 4.2v. LiitoKala Lii 100 overcharge to 4.24v and lowest voltage was in Nitecore F1, just 4.09v. All other charge from 4.15 to 4.18 volts. (I mean charger cutoff voltage, not battery voltage after charging)

    Then I thought about it. Is there a charger with cutoff voltage at exact 4.2v? I began to search and came across an interesting article on Tesla's website
    This post was published more than 10 years ago!
    https://www.tesla.com/blog/bit-about-batteries

    It says:

    "Voltages over 4.15V/cell (about 95 percent state of charge [SOC]) and voltages below 3.00V/cell (about 2 percent SOC) cause more stress on the insides of the cell (both physical and electrical)"

    "There is a huge difference in cycle life between a 4.2V/cell charge (defined by the manufacturers as “fully charged”) and a 4.15V/cell charge. 4.15 volts represents a charge of about 95 percent. For this reduction of initial capacity (5 percent), the batteries last a whole lot longer. Unfortunately, further reduction of charge has a much smaller benefit on cycle life."

    a huge difference in cycle life between a 4.2V/cell and a 4.15V/cell charge
    the batteries last a whole lot longer

    What does that means? How many more cycles? dozens? hundreds?
    Is this relevant for modern high capacity batteries like GA, MJ1,
    35E ? Does anyone have the experience of cycle to cycle overcharging or undercharging? How does this affect the batteries in real life use?

  2. #2
    Modernflame's Avatar
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    Default Re: Charging Li-ion to 4.1X v

    I'm also looking forward to some expert input here. Since I stumbled across similar findings about a year ago, I never charge my cells beyond 4.15, usually no more than about 4.12, although I do have chargers that will push li-ons to 4.2 However, it's only been a year and I have no way to measure or verify any improvements to the longevity of these cells.
    “May it be a light to you in dark places, when all other lights go out.”
    J.R.R. Tolkien, The Fellowship of the Ring

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    Default Re: Charging Li-ion to 4.1X v

    I usually take my batteries off early for torches, as I almost never charge up Li-Ion to max.

    After I found my laptops and mobile phone batteries ( routinely charged up to 100% ) losing capacity early, I have since switched to using a timer to keep them typically at or just under 80% SoC ....

    Should really be able to custom set "max" state of charge, in my opinion.
    Last edited by archimedes; 09-17-2017 at 06:50 PM.
    ... is the archimedes peak

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    Flashaholic* stephenk's Avatar
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    Default Re: Charging Li-ion to 4.1X v

    I tend to only charge to 4.2V if I know I'm going to be using the light within the next 24 hours, or need to balance batteries for use in series or parallel.

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    Default Re: Charging Li-ion to 4.1X v

    Yes, good point Stephen, in the very rare case I use a Li-Ion series setup ... I use matched sets, topped up to max
    ... is the archimedes peak

  6. #6

    Default Re: Charging Li-ion to 4.1X v

    In some laptops and phones there is an software option that limits charge to 80% or 90%. But is it so necessary?

    Typical 18650 rates to 500 charge/discharge cycles. Let's took half - 250 cycles.

    Let's imagine that I use flashlight 8 hours every night (full night) and have only one 18650. Zebrlight SC63w and NCR18650GA. I use medium mode 60Lm/33hrs. So I need to charge battery every ~4 days.

    250 * 4 = 1000 days = ~3 years to reach half rated cycles!

    Otherwise if I have 3 batteries and use charger twice a week (replace battery in flashlight twice a week) it will take ~8 years!!! to reach half of batteries rated cycles.

    3 batteries * 250 cycles each = 750 cycles / 2 cycles per week = 375 weeks = ~94 months = ~8 years!

    For such long periods of time, lithium aging will have a much greater effect on capacity than charge/discharge cycles, I guess.

    I'll just take the batteries to recycling in "X" years and will buy new. But why are so many people worried about this? Why Tesla worried? Maybe batteries are aging much faster if they are connected in packs?

  7. #7

    Default Re: Charging Li-ion to 4.1X v

    English is not my native language. I easily read and understand speech, but it's hard for me to write correctly, especially on technical topics.

    Maybe someone can send email to Sanyo or Samsung or LG or other lead manufacturer with a request to explain more detail batteries wear.

  8. #8
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    Default Re: Charging Li-ion to 4.1X v

    Specialized replacement battery packs may be very expensive, and there now also seems to be an increasing trend towards integrated (non-replaceable) batteries
    ... is the archimedes peak

  9. #9

    Default Re: Charging Li-ion to 4.1X v

    Battery university has some tables where tests were done concerning this. Charge/ effective full cycle count : 4.25v/200-350 cycles: 4.2v/300-500 cycles: 4.1v/600-1000 cycles: 4.0v/ 1200-2000 cycles. For me this is important when it comes to my iphone. I tend to keep a cellphone for about 4 years before replacement and it has never been for a weak battery. Charging every day 365x4 is 1400 or more cycles before it gets replaced. I try to get my phone to 90 ot 95% state of charge and not go below 30%, but then if they allowed USER REPLACABLE batteries i wouldnt worry about it so much. For flashlights 18650 and 14500 which i use i dont worry about it so much as i maybe put 20 to 40 cycles a year on a battery.

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  11. #11
    Flashaholic* TinderBox (UK)'s Avatar
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    Default Re: Charging Li-ion to 4.1X v

    Buy some 4.35v li-ion cells and only charge them to 4.20v no special equipment required.

    John.
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    Default Re: Charging Li-ion to 4.1X v

    One benefit of fully charging to 4.2v, is that flashlights with FET drivers will have greater output. At least, until the battery depletes down to a lower voltage. Even without a FET driver, I've noticed that a lot of high-powered "constant current" lights still drop quite a bit in output as the voltage goes down.

    I like keeping a fully-charged cell in a thrower (programmed to a single mode of max). Because, with a thrower, I want full power!

    For EDC, not so much.

  13. #13
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    Default Re: Charging Li-ion to 4.1X v

    I have some pany A and pany A cells still in use from...........well must be an easy 5 or 6+yrs. Its that far back i can not remember. Not noticed anything untoward and all my cells are charged to 4.2v or there about. I dont recall any of my cells ever being bellow 4.16-4.18v after being left to sit a while. Although charging to a lower V may benefit these cells, they are so cheap and usually surpassed 12m on.

    Certainly having a charger that can be pre set to 4.1v helps, even taking off the charger before terminating. But for me, the inconvenience is not worth it. Cells that dont get used are stored at a lower V if its months not weeks between uses. Other than that i simply charge up, use and swap out then rotate. Cells age anyway, so i would rather cut down my stock and use the ones i have,rather than sit on many for long term(years). I have been using more cells rather than keep buying new, so now my stock of stored 3.6-3.8v cells are around 20. I should be good for a bit flashlight wise(vape cells get replaced quicker). I dont want a pile of sony vtc4 when i could have vtc7's basically(example).

  14. #14
    ven's Avatar
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    Default Re: Charging Li-ion to 4.1X v

    Quote Originally Posted by TinderBox (UK) View Post
    Buy some 4.35v li-ion cells and only charge them to 4.20v no special equipment required.

    John.

    I have actually done that John, with my KeepPower 16650's in work for my surefires. I have the sanyo 16650(naked) cells in use, these are still charged to 4.35v .

  15. #15
    Flashaholic* TinderBox (UK)'s Avatar
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    Default Re: Charging Li-ion to 4.1X v

    Quote Originally Posted by ven View Post
    I have actually done that John, with my KeepPower 16650's in work for my surefires. I have the sanyo 16650(naked) cells in use, these are still charged to 4.35v .
    I was charging the 4.35v 18650 you gave me today, Thanks

    Trying out my new MiBoxer C2-3000 charger, charging every nimh and li-ion i can get my hands on, It`s very gentle on your battery`s in auto mode, the remaining time function is a total waste of time as it gets the time so so so wrong, best ignored.

    Good value at £19 with a 3 year warranty.

    John.
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    Default Re: Charging Li-ion to 4.1X v

    Welcome John

    Been checking a few chargers out, the dragon and mc3000 still seem up top right now. Still cant decide on what to get next..........

  17. #17
    Flashaholic* TinderBox (UK)'s Avatar
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    Default Re: Charging Li-ion to 4.1X v

    Not a big fan of the display on the dragon, looks like you can only see 2 channels at a time, and i rarely use my mc3000 as it`s massive and i cannot keep it out or my cats will get it.

    I am looking at the Gyrfalcon All-44 or the Nitecore SC4

    John.
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  18. #18
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    Default Re: Charging Li-ion to 4.1X v

    Yes agree on the dragon display, not keen on it not having a low charge rate either(for my smaller cells). If you decide one day the mc3000 wont get used, i may be tempted to buy off you(no rush)

    The 8 channel gyrfalcon would come in handy for me !

  19. #19
    Flashaholic* TinderBox (UK)'s Avatar
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    Default Re: Charging Li-ion to 4.1X v

    Damn, The Gyrfalcon All-44 and 88 cannot charge D size battery`s or maybe 2 squeezed into the outer slots.

    John.
    SkyRC MC3000 - Maha C9000 - LaCrosse BC-900 - Floureon BT-C3100 V2.2 - Accumanger 10 and 20 -Thunder AC6
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  20. #20
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    Default Charging Li-ion to 4.1X v

    If anyone seriously interested in batteries is not sure which charger to get, and the MC3000 is a candidate (not ruled out by price), then get it. Simple as that, IMHO.

    I've become a bit of a collector I guess, and have the Gyrfalcon All-88, SC4, and a bunch of others.

    Don't get me wrong, my impression of the SC4 so far is pretty good as well, and I just ordered a second one. It does what I need to do as a matter of routine pretty well, such as charging 18650a and Eneloops, while keeping an eye on internal resistance.

    There are things it just won't do though, that the MC3000 does, such as charging to 3.92V (or most other voltages within range) when I take a battery out of rotation.

    Edit to add: with the SC4, i haven't checked termination with Eneloops, but it charges the cells without me noticing a worrying temperature increase, so I'm carefully optimistic. It'll also default to 2A on 18650s, which is fine for me, but might be a bit high for some batteries.
    Last edited by terjee; 09-21-2017 at 01:05 PM.

  21. #21

    Default Re: Charging Li-ion to 4.1X v

    Quote Originally Posted by TinderBox (UK) View Post
    Not a big fan of the display on the dragon, looks like you can only see 2 channels at a time, and i rarely use my mc3000 as it`s massive and i cannot keep it out or my cats will get it.

    I am looking at the Gyrfalcon All-44 or the Nitecore SC4

    John.
    Agreed. I have always felt that the display lettering on the Dragon could be half the size, and show all four channels simultaneously, rather than just two at a time. As it is now, it looks like it's designed for the visually impaired lol.

  22. #22

    Default Re: Charging Li-ion to 4.1X v

    My i4 on the other hand charges it to 4.25v. Is it lethal for the battery, or is is still ok?

  23. #23
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    Default Re: Charging Li-ion to 4.1X v

    Have you verified away from the charger with another source(multi meter for example). It is right at the spec limit, most chargers are + or - 0.05v, so 4.15v to 4.25v is within spec. Personally i feel its a little high and would prefer a termination V closer to 4.2v. Other option is remove off charger before charge is completed. Inconvenient granted, but just a thought if your in the vicinity.

  24. #24
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    Default Re: Charging Li-ion to 4.1X v

    I have noticed that good quality chargers set to the correct charge rate (e.g. using 0.5A for 18650 is too slow!) tend to result in cell voltages that droop slightly once finished, down to somewhere between 4.15V - 4.18V. Personally I think this is a Good Thing - the cells will last longer. Capacity wise you aren't missing out on much. Someone pointed out that FET drivers may be slightly dimmer; while that may be true the flashlight will quickly drop down in brightness anyway as a change of 4.2V - 4.1V is somewhere around 10% of the capacity if I recall correctly.

    If you use a quality charger and set the current too low the cell tends to stabilise closer to 4.2V when finished. I guess people who mind the voltage droop can do this.

    Personally, I say accept the slight droop and enjoy the longer life expectancy of the cells.

  25. #25

    Default Re: Charging Li-ion to 4.1X v

    Do you need more cycles is a different discussion. For some uses like flashlights maybe few hundred cycles is enough. However there are other applications where you need/want more:
    - EV cars
    - phones/laptops
    - battery powered robots

    My EV car actually has a configuration to choose between 100% and 80% charge limit specifically for longer lifespan. So yes it has huge impact and some EV drivers are starting to supply real life data.

    The biggest factor on lifespan is intensity of cycles combined with max charge limit. For EV cars the worst performance was in hot states (Arizona, Florida, California) that have:
    1) higher temps
    2) intense cycles due to high speed driving = higher power = more heat
    3) full 100% charge

    So if you drive on highway causing 1C-3C power on battery, then immediately charge hot pack to 100% then drive again, etc You have high intensity cycles combined with full charge and batteries can die pretty early. There are talks about battery behavior and the point was that most degradation occurs in top 10% and bottom 10% (roughly). Meaning if you stay in the 20%-80% SOC range you can easily double or triple or increase even more lifespan.

    Again for flashlights it may not matter since LEDs use little power compared to electric motors on EV cars and robots. However for cars and robots batteries can die early. For cars in particular batteries and replacement work is super expensive so it does matter.

    Not that it is super important, but if you are using old cells pulled from laptop packs then lower charge voltage can help keep them alive bit longer. It depends on your cell use, how often you use them.

  26. #26
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    Default Re: Charging Li-ion to 4.1X v

    Agreed completely and my own experience mirrors this. I do acknowledge that if the user is willing to take a hit on cycle life for an application such as a flashlight with easier to replace/cheaper cells, then perhaps it is worth having a function added to chargers going forward. It would work by waiting for the charge to end, waiting another 30-60 minutes, and if the voltage has dropped to the 4.15-4.18V range it could then resume charging using a slower charge rate. Nothing unsafe about that, simply a loss of cell life. However it would give people the extra <10% of power that can't always be squeezed in by a fast charger that stops at 4.2V exactly when charging at a higher current.

    The 20-80% SOC rule is one I always try to follow for devices with expensive/difficult to replace cells such as certain laptops and my mobile phone. I have managed to stretch the battery lifespan of my 2 year old cellphone to the point that it almost holds the same charge it did when new because I avoid charging it to 100% at night if the battery is >=80%, and charge before it hits 20%. This will be impractical to those who heavily use the phone however!

    My Samsung laptop also has an option in the BIOS for extending battery life time. It limits the battery to 80% SOC during charging. I also noticed another interesting quirk: If you charge the battery and then let it drain to say 92% and plug in the charger, it does not charge it. It seems to be some method to extend the battery life.

  27. #27
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    Default Re: Charging Li-ion to 4.1X v

    There’s no need to wait, really.

    If you select 2A on a charger, it’ll actually charge in two phases. First a constant current phase, where it charges at 2A. Then, when it reaches 4.2V, it changes to constant voltage mode, and just holds that 4.2V until the current drops to 10% of the initial current. A bit simplified as chargers deviate all the time, but that’s the basics of it.

    What you can do, if you really want to max out, is to just slide those values around. If you terminate at 20% for example, you’d get some more life. Same if you’d switch mode and hold at 4.1V instead of 4.2V, that’d about double cycle life. Or you could terminate at 1% instead of 10%, and most batteries would hold at 4.2V (or so), and drop down less.

    Speaking from (empirical) experience here, the MC3000 lets you do all of these things if you’d like.

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