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  • Lithium Ion 18650

    This question is not really directly related to solar, but rather batteries. I have a bunch of 18650 cells that I scavenged from old laptop batteries. I would like to charge them to determine their capacities. I read around that charging to 4.2v lessens their lifespan and 4.1v is recommended. I have an IMax B6 charger and it defaults to 4.1v for Lithium Ion cells, which I was reading is around 80% of their capacity. If I charge the cell to 4.1v and a discharge to 3.0 volts yields 1200mah, is it safe to assume that the cell's capacity is 1500mah since 1500*0.8=1200 (these numbers are an example, not my actual cell).

    Or... should I just charge it to 4.2v and discharge to 3.0 to determine capacity, even though it gets very warm around 4.2v?

    Thanks.
    Last edited by mikes; 05-28-2016, 08:40 PM.

  • #2
    Just knowing that it is 18650 (a physical size) does not tell you what the chemistry is. And they are all Lithium Ion.
    LiFePO4 has very different voltage characteristics from other common Li chemistries.
    Do not try to charge them to 4.2 volts unless you know for sure what type you have!
    For more info go to http://www.candlepowerforums.com
    Last edited by inetdog; 05-28-2016, 09:59 PM.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #3
      I agree with the comment that you cannot tell by the size alone what chemistry the batteries are, but you can be reasonably confident that these batteries are not LiFePO4 batteries as they are from a laptop computer.

      To run a capacity test 4.2 volts to 3.0 volts is OK, but not for everyday use. some more information can be found here.http://batteryuniversity.com/learn/a..._ion_batteries and here http://batteryuniversity.com/learn/a...ased_batteries

      With these batteries make sure that the charge current is limited to 1 amp. Too high a charge current at 4.2 volts will overheat your battery.

      Simon
      Off-Grid LFP(LiFePO4) system since April 2013

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      • #4
        Ditto, 18650 just means they are 18 mm diameter, and 650 mm long. It does not tell you what chemistry they are. Depending on type the charge voltage ranges from 2.85 for Titinate up to 4.3 for LiPo. So if those happen to be say LiFeP04 and you charge them to 4.1, you can do a lot of damage as they are charged to 3.65 volts.

        Lastly using voltage to determine SOC for lithium batteries is pretty much pointless as the discharge curves are just too flat.
        Last edited by Sunking; 05-28-2016, 10:53 PM.
        MSEE, PE

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        • #5
          Originally posted by mikes View Post
          This question is not really directly related to solar, but rather batteries. I have a bunch of 18650 cells that I scavenged from old laptop batteries. I would like to charge them to determine their capacities. I read around that charging to 4.2v lessens their lifespan and 4.1v is recommended. I have an IMax B6 charger and it defaults to 4.1v for Lithium Ion cells, which I was reading is around 80% of their capacity. If I charge the cell to 4.1v and a discharge to 3.0 volts yields 1200mah, is it safe to assume that the cell's capacity is 1500mah since 1500*0.8=1200.
          Nope, not a safe thing to assume.

          First off if they are getting hot do not use them with that charger. Li-ions charged within their specs (i.e C/2 or whatever they are rated for) should not get "very warm."

          Second if they are old they might be coke rather than graphite anode; coke anode has a max charge voltage of 4.1 volts anyway.

          If they are old and out of laptops it is unlikely that they are LiFePO4. LiFePO4 in the 18650 form factor is a relatively recent development, and have not been used significantly for laptop batteries.

          Do they have any markings at all?

          If you do a charge/discharge cycle the main part of the discharge curve (average discharge voltage) will tell you a lot. If it's around 3.6/3.7 volts at around C/5 it's probably lithium ion/graphite. 3.5/3.6 volts is probably lithium ion/coke. 3.3 or so is probably LiFePO4. If their discharge impedance is more than a few ohms then the cells are shot.

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          • #6
            Thanks guys, very helpful. I am 100% certain they are Lithium Ion, as I pulled them from the packs myself. They are not "very old" maybe 2 years max. I have a lot of CGR18650CE/MH12210. With a quick google search, people can't seem to agree on what they actually are capacity-wise. I'll stick with 4.1v to be safe.

            I also have a pile of SANYO-UR18650A. The spec sheet says 3.6v but charge at 4.2v. Does that mean I should still charge to 4.1?
            http://www.wickedlasers.com/image/wi...ifications.pdf
            Last edited by mikes; 05-29-2016, 08:29 AM.

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            • #7
              Originally posted by mikes View Post
              Thanks guys, very helpful. I am 100% certain they are Lithium Ion, ]
              Mike you are not getting it. Lithium Ion does not tell you what kind of Lithium Ion Battery you have. You are playing with fire. That is what we have been trying to tell you in this post and your other post. Secondly if the batteries get warm while charging, something is wrong. It either means:

              The batteries are shot
              Charging too fast
              Charging at to high of a voltage.

              Lithium Ion Battery does not mean anything, it is a generic term like Soda Pop. Does not tell you or anyone what flavor it is.

              Anyway CGR18650CE/MH12210 is a generic Panasonic designation. They can be 2200 (Standard Grey) or 3100 (Green Super) mah and can be 3.6 or 3.7. Charge no higher than 4.2 volts. Just because you can go as high as 4.2 volts, does not mean you should go that high. These batteries are unprotected versions and discontinued. They are made for laptops, ecigs, and vaporizers.
              Last edited by Sunking; 05-29-2016, 11:27 AM.
              MSEE, PE

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              • #8
                Originally posted by Sunking View Post
                Mike you are not getting it. Lithium Ion does not tell you what kind of Lithium Ion Battery you have. You are playing with fire. That is what we have been trying to tell you in this post and your other post. Secondly if the batteries get warm while charging, something is wrong. It either means:

                The batteries are shot
                Charging too fast
                Charging at to high of a voltage.

                Lithium Ion Battery does not mean anything, it is a generic term like Soda Pop. Does not tell you or anyone what flavor it is.
                Did you even bother reading the entire post? I included two very specific model numbers off the cells and a link to the spec sheet for one of them. I am not guessing, I am trying to research and learn. I understand the statement made previously about them getting hot and as such have not charged any since until I can figure out what exactly I am working with.

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                • #9
                  Originally posted by mikes View Post
                  Did you even bother reading the entire post? .
                  You still don't get it, you keep saying Lithium Ion. Lithium Ion what?

                  Cobalt, Manganese, Iron Phosphate, Titinate.

                  WTF are they? You can't answer because you do not know what you are doing.That is why you just keep saying Lithium Ion. You do not know there are several types and each has its own unique characteristics like charging voltages.

                  CGR18650CE/MH12210 is a generic Panasonic designation that can be 1 of 2 types. Are they Green, Lime Green, or Gray. There are no longer made by Panasonic and only Chi-Coms make copies.

                  So here is what you need to know. Since you cannot identify if they are LiCo or LiPo, do not charge higher than 4.2 volts. 4.0 to 4.2 is good enough to be safe.
                  Last edited by Mike90250; 05-29-2016, 07:06 PM. Reason: vulgarity deleted
                  MSEE, PE

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                  • #10
                    Originally posted by mikes View Post
                    I also have a pile of SANYO-UR18650A. The spec sheet says 3.6v but charge at 4.2v. Does that mean I should still charge to 4.1?
                    The UR18650A is a cobalt based, graphite anode lithium ion and is normally charged at 4.2 volts. Charging to 4.1 volts will extend their life a bit at the cost of some capacity (10-20%.)

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                    • #11
                      Originally posted by jflorey2 View Post
                      The UR18650A is a cobalt based, graphite anode lithium ion and is normally charged at 4.2 volts. Charging to 4.1 volts will extend their life a bit at the cost of some capacity (10-20%.)

                      Thank you. I was not aware there was multiple chemistries of "lithium ion". I appreciate the helpful information.

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                      • #12



                        Originally posted by Sunking View Post
                        You still don't get it, you keep saying Lithium Ion. Lithium Ion what? Cobalt, Manganese, Iron Phosphate, Titinate.
                        I was not aware there were subcategories of these battery types. You kept talking about "cobalt" and I thought that was an entirely different chemistry. I explained numerous times that I'm here to learn but your "you're doing it wrong" attitude makes it very difficult for me to get accurate information.


                        Originally posted by Sunking View Post
                        So here is what you need to know. Since you cannot identify if they are LiCo or LiPo, do not charge higher than 4.2 volts. 4.0 to 4.2 is good enough to be safe.
                        Thank you.
                        Last edited by Mike90250; 05-29-2016, 07:05 PM. Reason: vulgarity deleted

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                        • #13
                          Originally posted by mikes View Post
                          I was not aware there were subcategories of these battery types..
                          Yes I know, that is what we keep trying to tell you.

                          Lithium Cobalt Oxide or LCO or LiCo: First commercial release. Used in Laptops, Cell Hones, and Tesla Forst release EV. Very unstable and the type that gives lithium a bad name.

                          Lithium Nickel Cobalt Aluminum or NCA. Highest energy density of all the Lithium batteries, Very unstable and requires thermal and charge\discharge management

                          Lithium Manganese Oxide LMO: Safer than LCO but poor high tempuratue. Type used in Nissan Leaf EV

                          Lithium Iron Phosphate LFP Safest most stable with high power output but low energy density. Directly compatible with Lead Acid. Best choice for solar and Renewable energy.

                          Lithium Nickel Manganese LMO: Not used much.

                          Lithium Titinate LTO: Extremely safe and longest cycle life but poor energy density

                          There are more I have not mentioned. Point here there are a lot of them, and each has its own unique application, operating and charge voltages. All 6 above come in 18650 cylinders. What is in them is what you have to know, not what container it comes in. But here is what is important. LFP is the only type compatible with off the shelf solar equipment as it has the same charge requirements as lead acid batteries. It is also one of the safest most tolerant to abuse making it DEFAULT CHOICE for home-owners.

                          Some commercial systems use other types. But they are proprietary using custom designed chargers and controllers made specifically for the type of battery they use. So when you say Lithium battery does not mean anything. Go into a bar and order a Soda Pop. You are going to get a dirty look because you are not telling the bar tender anything except gibberish.
                          Last edited by Sunking; 05-29-2016, 04:25 PM.
                          MSEE, PE

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                          • #14
                            thread closed, cells were heating up and about to light a fire
                            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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