Klarus        
Results 1 to 4 of 4

Thread: NCR18650B cells unreliable

  1. #1
    Unenlightened
    Join Date
    Feb 2019
    Posts
    2

    Default NCR18650B cells unreliable

    Iíve been trying to troubleshoot a problem, but I think I have narrowed it down to the batteries, so Iím posting in this thread for some help.

    Based on the review published here at CPF, I purchased a Jetbeam BC-40 in late 2012, and I also picked up an intellicharger i4 charger, and a couple of NiteCore 2300 mAh 18650 batteries.

    This combo has worked well as a bicycle headlight, though I needed higher capacity batteries for longer ride times, so I picked up some Made in Japan 3400 mAh 18650B cells from r-l sales. Iíve also used these cells in a homemade sled to power my taillight (DesignShine DS-500).

    Hereís the problem.
    Late in 2015, I purchased some additional Made in Japan 3400 mAh 18650B cells from GearBest. These seemed to be fine, though I only rarely used them when my other cells were in need of charging.

    I eventually soldered up a 4-cell battery sled (2S2P), and it worked fine to power my taillight using the GB cells during a 4-hour test run in my living room. Unfortunately, the taillight stopped working during my second ride while using the 4-cell sled with the GB cells. I found that jostling the battery pack can interrupt the circuit, but I inspected all of the solder joints and they were good.

    In trying to troubleshoot, I tried the same GB cells in the Jetbeam, and gave it some hard bumps with my hand to simulate hitting a rough patch of pavement; the light would flicker or quit almost every time. When I removed the cells I noticed that the negative contact on both cells was now concave after tightening the end cap all the way. The r-l sourced cells have never flickered during a ride.

    Are the GB cells possibly defective? Apologies if this is this a known issue that has been discussed here previously.

    The GB cells work fine unless they are jostled in a flashlight or sled, so I donít trust them for use on a bicycle or being handled roughly. Do I write these off for on-road use?

    L-R: GB cells 1-4, r-l cells 5-6
    Cell 3 with concave negative contact


    Cells lined up next to 2-cell sleds I purchased awhile back. This style has worked fine for years, though the contacts are exposed and need to be covered with tape.



    L-R: GB cells 1-2, r-l cells 3-4

  2. #2
    Flashaholic* vadimax's Avatar
    Join Date
    Dec 2015
    Location
    Vilnius, Lithuania
    Posts
    1,988

    Default Re: NCR18650B cells unreliable

    There are two purely mechanical issues:

    1. The wider the contact surface the easier to crush it;
    2. If you do not use springs or cushions of any sort your batteries will be crushed with almost 100% probability.

    If your batteries do not ďfloatĒ on springs or cushions you have to attach them in such a way that only external perimeter on the edges of the cylinder (the strongest part) would accept mechanical pressure, not fragile contact surfaces.

  3. #3
    Flashaholic*
    Join Date
    Nov 2007
    Location
    Germany
    Posts
    726

    Default Re: NCR18650B cells unreliable

    Your cells are of the "protected" type, which is very advisable in multi-cell flashlights like the BC40. This means they have an additional electronics module in the small black disc at the end (see https://lygte-info.dk/info/isMyBatte...cted%20UK.html for lots of pictures and a short explanation). You can see that this additional stuff looks different in the GB vs the r-l cells on your first picture.

    You might have broken some electrical connections in the protection electronics by forcing the GB batteries into that battery carrier. I have some cells here that look identical to your GB cells in every way (that I bought cheap from some chinese dealer) and, while performing very well, they are rather long. All of mine are slightly dented as well because they are a tight fit in many flashlights.
    happens

  4. #4
    Unenlightened
    Join Date
    Feb 2019
    Posts
    2

    Default Re: NCR18650B cells unreliable

    Quote Originally Posted by Helmut.G View Post
    Your cells are of the "protected" type, which is very advisable in multi-cell flashlights like the BC40. This means they have an additional electronics module in the small black disc at the end (see https://lygte-info.dk/info/isMyBatte...cted%20UK.html for lots of pictures and a short explanation). You can see that this additional stuff looks different in the GB vs the r-l cells on your first picture.

    You might have broken some electrical connections in the protection electronics by forcing the GB batteries into that battery carrier. I have some cells here that look identical to your GB cells in every way (that I bought cheap from some chinese dealer) and, while performing very well, they are rather long. All of mine are slightly dented as well because they are a tight fit in many flashlights.
    To clarify a bit, the dented cells were inserted into the flashlight, not the Keystone 1048 sled.

    Here is a picture of the BC-40 and DIY mount. The tailcap has a standard spring contact.



    Here is the 2S2P holder.



    Although I tried using 4 r-l cells, I was still able to interrupt the circuit by bumping the top of the holder, but not the bottom or sides. I wonder if the cells are losing contact at the bottom of the holder since there are no springs there? It may not actually be a battery issue after all. I may try to use a couple of 1048 sleds instead.

    Can anyone recommend a 4-cell sled that will fit the longer (69mm) protected cells? Itís been awhile since I searched. Thanks.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •