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Charging the NCR18650B 20ah pack with the Luna charger.

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    Charging the NCR18650B 20ah pack with the Luna charger.

    Hello everyone,

    I was wondering if charging the NCRb 20Ah pack always at 5 amp (luna charger) is a good thing (at ambient temp). I'm pretty sure I have answered my question below, I just want to get opinions!

    The panasonic website recommends 0.5c of charge of the nominal minimum capacity of 3250mAh, so 1625mAh. considering the pack is a 6P, that means I could charge at 9,750A all the time to get 400 cycles. So charging it at 5A (+-0.25c) should be perfect?

    Now charging the pack at 3A is 0.5A/cell is 0.15C...I wonder if it's too low? I know charging a battery with too low current is not good, but how low is too low?

    Next question to the Luna charger owners,

    What is the final voltage after charging to 90% and 80%?

    Thanks

    Seb

    #2
    No love for the subject?

    Comment


      #3
      Originally posted by Sebz View Post
      I know charging a battery with too low current is not good, but how low is too low?

      Seb
      Never heard that before. I always thought charging at low amperage was good for the battery -- as long as you have the patience to wait for the job to complete!

      Comment


        #4
        Yes, the slower you charge is always better. I've never heard of a minimum charge rate before. If it were true, then regen braking would be more complicated and difficult. The regen on my hub charges at different rates, depending on the speed I'm slowing from.

        That being said, there is a point of diminishing return on slow charging. On a 20 amp hour pack, charging any slower than 3ah wouldn't provide much further longevity to your cells since you're already charging at such a low rate per cell. From what I've heard, the sweet spot is a charge rate that would reach full in about 4-5 hours, as a balance between charge time vs charge rate.

        Comment


          #5
          To my knowledge Li-ion cells have a minimum charging amperage, I do not know the exact science for this, I can only say I currently work in the uninterruptible power supply (UPS) industry as a technical service manager, although we still use lead-acid batteries, the use of Lithium batteries was deeply studied and I remember something about this minimum charging current at some point and something about charging efficiency. But I could be wrong, I'm still learning ALOT about li-ion cells.

          Recently I came across Bruno's Youtube channel and he spoke about it but didn't go into details.

          Look out Bruno on youtube, he seems very knowledgeable!

          This video at 4:30

          https://www.youtube.com/watch?v=M41BB5g05bI



          The reason im asking is that I could not find the minimum charging specs on the NCRb, I did find one for the NCRpf and it's clearly 0.6A, So if it's the same on the B, it should be 0.6x6= 3.6A minimum charging current....need proof? Look in bold.



          SPECS NCRpf
          Panasonic 18650PF
          Specifications: Battery type: 18650
          High Drain | Hybrid IMR
          Capacity: 2900mAh
          Max Discharge (constant current): 10A
          Max Discharge Pulse Current (5-6 sec.): 18A
          Full charge: 4.2V Charging method: CV/CC
          Minimum charging current: 0.6A
          Rapid Charging current: 1.35A
          Nominal (storage) voltage: 3.6V-3.7V
          Minimum discharge voltage level: 2.5V
          Dimensions: 18.5mm x 66.5mm *18 mm x 65 mm
          Weight: 46.5g
          Button Top: Yes *No


          Good night!
          Last edited by Sebz; 04-22-2016, 07:16 PM.

          Comment


            #6
            Interesting observation! Now that I check, I see that my Panasonic NCR18650PF cells have the same 0.6A minimum charge rate specification.

            My 14S 52V pack gets only 0.36A/cell at the higher 5A setting, and 0.21S/cell at 3A. You are way above that, at least.

            I don't know what this recommended lower limit is based upon. But I'm sure Panasonic has researched their chemistries well enough to be right about it, as far as achieving the advertised performance. They don't make these things up. Charging more slowly than recommended is probably not optimal for maximum life. I guess I'll stop using the 3A setting, and stay as close to the specification as I can.

            Anybody know more about this?
            Last edited by JPLabs; 04-22-2016, 09:57 PM.
            Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

            Comment


              #7
              Sebz.Thanks for the you tube link. Need to find out more about my cells. I have a 3a/5a Luna charger and maybe I need to be charging them at 5 amps to 80% for maximum life.

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