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Thread: Question about best charging current.

  1. #1

    Question Question about best charging current.

    Hello,

    I own a Liitokala 500S charger and I wonder what would be the safest current settings for testing and charging Ion Li batteries, specially 18650. I can choose from 500 maH to 2000 maH but I'm afraid higher currents despite of charging faster can be dangerous for battery cycle. Any ideas?

  2. #2

    Default Re: Question about best charging current.

    With 0.3C you are always on the safe side

  3. #3

    Default Re: Question about best charging current.

    Quote Originally Posted by sbj View Post
    With 0.3C you are always on the safe side
    Well, in my case 500mah thatís the minimum.
    Thank you!

  4. #4

    Default Re: Question about best charging current.

    That depends how fast you want those cells charged and how many cells you have. Ideally, 1 amp is a fine balance of cycles and waiting for them to be done. 500mA if you have spares and/or time isn't a factor

    Currents around 1.5mA or higher
    Would be a last resort charge current option for urgently needing them like an emergency situation like an impending power outage or forgot to charge but suddenly needing them right away.

    In my opinion 1.5 that's when heat generation most likely to happen. Whether it's from the charger itself or from the cells. Heat will for sure degrade cycles faster. I rarely charge my cells no higher than 1A.

    Hope this helps.

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    Last edited by MarioJP; 11-14-2020 at 09:13 AM.

  5. #5

    Default Re: Question about best charging current.

    Quote Originally Posted by MarioJP View Post
    That depends how fast you want those cells charged and how many cells you have. Ideally, 1 amp is a fine balance of cycles and waiting for them to be done. 500mA if you have spares and/or time isn't a factor

    Thatís what I want: faster charge/test but with safety.

    Currents around 1.5mA or higher
    Would be a last resort charge current option for urgently needing them like an emergency situation like an impending power outage or forgot to charge but suddenly needing them right away.

    In my opinion 1.5 that's when heat generation most likely to happen. Whether it's from the charger itself or from the cells. Heat will for sure degrade cycles faster. I rarely charge my cells no higher than 1A.

    Hope this helps.

    Sent from my SM-A516U using Tapatalk
    Thank you so much. Much appreciated!

  6. #6

    Default Re: Question about best charging current.

    I tend to stick with 1A for charging my cells; fast enough for me and they remain nice and cool.

  7. #7
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    Default Re: Question about best charging current.

    Yeah, 1 amp is best for 18650's. You can go slower, but it's not going to result in any benefits. Only use 2 amps if the cell is made for high-drain (such as 20 amps or more). Of course, you can use 2 amps for 10A or 15A cells, and they'll take it okay, but it's a little harder on them.

  8. #8

    Default Re: Question about best charging current.

    I do want to mention that there are some chargers out there like mines that can charge cells up to 3 amps max! But i will never charge 18650 cells at that rate. That's too fast. Just because you can doesn't mean you should lol.


    Also, another thing that has me amazed are li-po cells and quick charge in mobile devices. How it manages to dump 3,000mah within an hour without much heat generated from the usb-c port and phone amazes me.

    The li-po that comes with my phone is rated 4500mah capacity and can easily handle 3A no problems.


    Does this mean that li-pos are more superior than cylindrical cells?

    Quick charge is right. An advancement of charging technology for phones and mobile devices lol.

    Sent from my SM-A516U using Tapatalk
    Last edited by MarioJP; 11-14-2020 at 09:52 AM.

  9. #9

    Default Re: Question about best charging current.

    0.4C is my ceiling when prioritizing longevity.

    Lower in cool ambients

    Higher does no harm when the cells are hot.

  10. #10
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    Default Re: Question about best charging current.

    Best safety margin is charging at 7/10 of cell capacity.

  11. #11
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Question about best charging current.

    1A all day, everyday, even for NiMH Eneloop AAs, 400-500mA for the AAAs.

    Chris
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  12. #12

    Default Re: Question about best charging current.

    Quote Originally Posted by MarioJP View Post
    I do want to mention that there are some chargers out there like mines that can charge cells up to 3 amps max! But i will never charge 18650 cells at that rate. That's too fast. Just because you can doesn't mean you should lol.


    Also, another thing that has me amazed are li-po cells and quick charge in mobile devices. How it manages to dump 3,000mah within an hour without much heat generated from the usb-c port and phone amazes me.

    The li-po that comes with my phone is rated 4500mah capacity and can easily handle 3A no problems.


    Does this mean that li-pos are more superior than cylindrical cells?

    Quick charge is right. An advancement of charging technology for phones and mobile devices lol.

    Sent from my SM-A516U using Tapatalk
    Thank you,Mario!


    Enviado do meu iPhone usando Tapatalk

  13. #13

    Default Re: Question about best charging current.

    Quote Originally Posted by ChrisGarrett View Post
    1A all day, everyday, even for NiMH Eneloop AAs, 400-500mA for the AAAs.

    Chris
    Good to know! Thatís what Iím going to do from now on.


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    Flashaholic* TinderBox (UK)'s Avatar
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    Default Re: Question about best charging current.

    I do as close as i can get 0.5C charge and 0.25C discharge for every type of battery chemistry unless i am in a hurry, Then it`s 1C charge and 0.5C discharge.
    "Build a man a fire, and he'll be warm for a day. Set a man on fire, and he'll be warm for the rest of his life." - Terry Pratchett.

  15. #15

    Default Re: Question about best charging current.

    Fot longevity the max discharge rate can go much higher than the charge rate.

    But the impact of both do vary a lot by temperature.

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    Flashaholic* fivemega's Avatar
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    Default Re: Question about best charging current.

    Quote Originally Posted by Hegner View Post
    Well, in my case 500mah thatís the minimum.
    mAh is measuring of battery capacity. So, you mean 500mA or 0.5A (1/2 A)


    Quote Originally Posted by Dascombe View Post
    I tend to stick with 1A for charging my cells; fast enough for me and they remain nice and cool.
    It depends on battery capacity and type. Charging a 10Ah battery at 1 Amp is 0.1C and charging a 1Ah battery at 1A is 1C (C is battery capacity)
    If your 18650 has capacity of 3300mAh then 1A charging current is about 0.3C and if it has capacity of 1950mAh, at same current 1A is about 0.5C

  17. #17

    Default Re: Question about best charging current.

    Quote Originally Posted by fivemega View Post
    mAh is measuring of battery capacity. So, you mean 500mA or 0.5A (1/2 A)

    Sorry, I meant 0.5A



    It depends on battery capacity and type. Charging a 10Ah battery at 1 Amp is 0.1C and charging a 1Ah battery at 1A is 1C (C is battery capacity)
    If your 18650 has capacity of 3300mAh then 1A charging current is about 0.3C and if it has capacity of 1950mAh, at same current 1A is about 0.5C

  18. #18
    Flashaholic* adamlau's Avatar
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    Default Re: Question about best charging current.

    I usually charge at or close to 1C (based on minimum specified capacity) unless the product data sheet for the cell indicates a lower maximum charging current.
    Last edited by adamlau; 11-17-2020 at 06:42 AM.

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    Default Re: Question about best charging current.

    Quote Originally Posted by adamlau View Post
    I usually charge at or close to 1C (based on minimum specified capacity) unless the product data sheet for the cell indicates a lower maximum charging current.
    That's probably too high, except for high-drain cells. For example, 3.5 amps is way too high for a Sanyo GA or Samsung 35E 3500mAh cell.

    But perhaps you meant 1A, not 1C.

  20. #20

    Default Re: Question about best charging current.

    1C is fine, if your use case demands a very high discharge C-rate also.

    But if concerned about longevity **and** your discharge C-rate stays under 1C

    then 0.4C is a good limit to stick to

  21. #21

    Default Re: Question about best charging current.

    Question. Let say you have a cell that is 4500mAh. So 0.5c equals around 2.2A correct? And will longevity be affected as well?

    I am trying to compare a li-po to a cylindrical cell. Do higher capacities means faster charging or is there a limit to which cylindrical cells can take without overheating?

    It just seems that this is an advantage that li-pos have over cylindrical cells. They can absorb large amount of currents without heating issues.

    Is this is also the reason why most consumer electronics use li-pos instead of cylindrical?

    Thanks.

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    Last edited by MarioJP; 11-25-2020 at 04:56 PM.

  22. #22
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    Default Re: Question about best charging current.

    Quote Originally Posted by MarioJP View Post
    Question. Let say you have a cell that is 4500maAh. So 0.5c equals around 2.2A correct? And will longevity be affected as well?
    Don't use capacity as guideline to how fast to charge. It makes no sense. Instead, use internal resistance as your guide. Low internal resistance means you can put more current into charging that cell (as well as discharge of course), without the resistance causing excess heat. Generally, that means lower capacity cells can actually take more charging current than high capacity cells. Because lower capacity cells are often high drain cells which have very low internal resistance. High capacity cells are designed for capacity, not power, so they have higher internal resistance.

    As a rough guideline, stick with 1A charging for cells rated under 10A discharge. 1.5A for cells up to 15A. And 2A for cells over 15A. You can probably double those rates if you really need to fast-charge your cells, but it will result in significantly decreased lifespan.

  23. #23

    Default Re: Question about best charging current.

    C-rate is **absolutely** the unit for current to use, but as you parallel your 4.5Ah cells, say to create an 18Ah pack, then your 0.5C becomes 9A, same as 2.25A per cell.

    What are you building the packs for? What is the use case? How big in Ah, what voltage? To be stored where, charged where, used where, doing what?

    LiPo is just a set of packaging criteria to get as light a battery as possible, and that is critical in flying models and consumer electronics.

    But it does not specify a particular chemistry.

    The cylindrical cells in 3.6-3.7V nominal range also can have any of a dozen different chemistries.

    Each with widely varying characteristics and behaviours, cycle lifespans, designed for high energy density vs high power density (in opposition to each other) etc

    Within those "families" of chemistries, longevity and safe charge rate is determined lots more by your knowledge level, care treatment protocols and reliability of your infrastructure gear (BMS, chargers, monitor/testers etc)

    than whether you are using NMC or LCO, LMO vs NCA.

    A key characteristic is likelihood of thermal runaway, explosively high burn rate that can quickly engulf your car or a large building full of people. Especially dangerous as they start to wear (SoH% lose capacity, increase ESIR) and most often while charging!

    That is **a lot** more important than your desired fast charging C-rate, or longevity etc.

  24. #24

    Default Re: Question about best charging current.

    I agree that **actual measured** ESIR is useful to determine the actual C-rate a cell can handle **for discharge**

    but that has nothing to do with the blatant lies marketeers use for rating cells.

    And a 20Ah battery will obviously handle a 10A charge rate

    while the same absolute amps may be super dangerous with even the best quality 2.5Ah cell of whatever chemistry, no matter cylinder or LiPo, no matter how low its resistance

    and certainly not conducive to longevity.

  25. #25
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    Default Re: Question about best charging current.

    Again, don't use capacity to determine what your charge rate is. Here is an example:

    Using two popular 18650 batteries:

    1. Samsung INR18650-25R

    2. Panasonic NCR18650B

    The Samsung has a capacity of 2500 mAh, with a max charging rate of 4000 mA. That's a 1.6C charging rate.

    The Panasonic has a capacity of 3350 mAh, with a max charging rate of 1625 mA. That's only 0.48C.

    You can clearly charge the Samsung at a much faster rate, even though it has much less capacity.

  26. #26
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Question about best charging current.

    If you want to Ďknowí the best charging rate for any particular cell, or battery, you need to seek out the manufacturerís data sheet.

    Chris
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  27. #27

    Default Re: Question about best charging current.

    The maximums they cite are "do not approach" extremes, for preventing immediate apparent damage.

    Not at all the specs conducive to maximising longevity.

    Not just current rates but charge termination voltages.

    4.05V up to maybe 4.10V is plenty to get to Full SoC when normal cycling, really no usable extra capacity, just reducing life cycles by going any higher.

  28. #28
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    Default Re: Question about best charging current.

    Quote Originally Posted by john61ct View Post
    4.05V up to maybe 4.10V is plenty to get to Full SoC when normal cycling, really no usable extra capacity, just reducing life cycles by going any higher.
    I normally do 4.10v, unless I'm planning on using it soon for an extended period of time. 4.1v is a lot easier on the cell. You do lose the top 10% of capacity, though. Not a big deal for most uses.

    You might get something like 600 cycles out of a 4.1v charge, vs. 300 cycles with a 4.2v charge. If you use that battery a lot (recharge every couple of days), that's a big difference. If you don't use your cells much, then it probably doesn't matter and you may as well use 4.2v.

  29. #29

    Default Re: Question about best charging current.

    yes, same as the other care factors

    if the use case necessitates "abuse" then so be it and just replace more frequently.

    With batteries costing under $100 nbd, if a bank costs thousands the you care more

  30. #30

    Default Re: Question about best charging current.

    Very informative thread. Just to clear things up. This was merely to try to understand that was lingering on my mind ever since quick charging was introduced.

    So i am using meter that measure the output current coming out from a quick charge usb charger.

    How Samsung manages to have a 4500mAh battery with qc mode. It dumps 3 amps throughout the charging process until it gets around 85%. That's when the current starts tapering off. Even at 85%, the charge current is still at 2 amps.

    I am curious what technology went into these samsung batteries for their devices.

    Apologies for the confusion lol.

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